Polyphenols are a class of organic compounds primarily found in plants that can be classified into four main families: lignans, phenolic acids, stilbenes and flavonoids. They play a number of critical roles including growth, pigmentation, pollination and resistance to pathogens of plants.¹ Polyphenols also influence the taste and colour characteristics of fruit and vegetables. Brightly coloured fruit including cherries, blackcurrants, blueberries, blackberries and pomegranate are particularly good sources of polyphenols, which have been investigated for their healthpromoting, anti-oxidant and anti-inflammatory properties.

• The promotion of fruit and vegetable intake to support general health has been advocated for years. A greater understanding of the emerging role of polyphenols in favourable health, exercise performance and recovery outcomes further strengthens the public health message to maintain a high intake of fruit and vegetables. A summary of emerging research on outcomes relating to exercise performance and recovery from polyphenol ingestion follows below. Polyphenols appear to mimic some aspects of exercise training and may have an additive effect alongside exercise.²
• Polyphenols, by virtue of their antioxidant and anti-inflammatory properties, may reduce oxidative stress, inflammation and muscle pain associated with muscle damage induced by exercise, thereby enabling an earlier return to normal muscle strength/force.^{2, 3, 4, 5, 6}
• Early studies on quercetin (a type of flavonoid) supplementation promoted reduced perception of exercise effort, perhaps related to improved blood flow, including cerebral.⁷
• A meta-analysis of studies on blackcurrants showed an overall improvement to performance of high intensity prolonged exercise, predominantly cycling, with a greater effect in higher level athletes than sub-elite.9 Polyphenols may also reduce muscle soreness and improved recovery post exercise.^{4, 5, 6}
• Flavonoids may reduce the incidence of upper respiratory tract infections in healthy adults.⁸
• Anthocyanins (a type of flavonoid) may enhance nitric oxide production, facilitating blood flow during exercise.⁷
• Tart cherries contain melatonin which may aid sleep.⁵

• In addition to whole fruit and vegetables, there are a number of supplemental forms in which fruit polyphenols may appear. These forms are summarised in Table 1.
• There are a number of products on the market, however many do not state the exact content of active compounds, which makes it difficult to determine an effective dose.

Table 1: Fruit-derived polyphenols and sport performance >

• The absorption and metabolism of most polyphenols is thought to be slow and incomplete. However, the benefits to gastrointestinal health and gut bacteria are likely to play an important role in the mechanism of action of polyphenols, but at this stage have been poorly investigated.
• Apart from quercetin, cherries and blackcurrant, there is insufficient human data to recommend an effective dosing strategy of other polyphenols.
  • Quercetin: 1000 mg/day for at least 7 days prior to competition.³ Effects of chronic intake uncertain but probably best avoided.
  • Blackcurrant: 105-210 mg blackcurrant anthocyanins/day for 7 days prior to competition.6 Effects of chronic intake uncertain but likely ill advised. The majority of research has been conducted on New Zealand black currant, however provided the anthocyanin dose is achieved, there is no indication that other products would not have equal efficacy.
  • Tart Cherries: 90-200 cherries (in the form of cherry juice, cherry juice concentrate or capsulated powder) in a split dose for 4-7 days before and 2-4 days after eccentric exercise or endurance exercise that induces inflammation (such as a marathon). This includes competition which must be repeated multiple times within one day or multiple times over consecutive days.
• Approximately 150g blueberries or 300g mixed berries is sufficient to achieve the polyphenol content provided in many research studies.

1. There remains little consensus on specific doses of most of these fruit polyphenols.
   • Athletes are encouraged to consume a wide range of fruits and vegetables within a well-chosen diet to supply a variety of phytochemicals.
   • Furthermore, there may be variations in anthocyanin content of different variants of berries according to the conditions they’re grown in.
   • Further research is required to compare different variants of berries, including their bio-availability.
2. The research may only be relevant to specific variants of the fruit – such as New Zealand blackcurrants, Montmorency cherries
   • It is important to check the source / variant of the fruit in any supplement.
3. Gastrointestinal distress in those with sensitive gastrointestinal tracts
   • Cherries are known to have a laxative effect, and high doses of other berries may also cause gastrointestinal distress in those with sensitive gastrointestinal tracts. This may be particularly of concern in athletes with physical impairments that limit voluntary bowel control. As such, increasing berry/ cherry intake or the use of berry/ cherry juices (or derived products) should be trialled outside of exercise first.
4. The role of flavonoids on upper respiratory tract infections in athletes is yet to be fully researched.
5. Research indicates consuming high doses of antioxidants and anti-inflammatory compounds reduce the adaptive response to exercise training.
   • While consuming a wide range of fruits is strongly supported in the daily diet of athletes, supplementation of high doses of these fruit-derived polyphenols is NOT recommended during day to day training periods.

Gatorade Sport Science Institute
www.gssiweb.org/docs/default-source/sse-docs/bowtell_sse_195-v3_final.pdf?sfvrsn=2

Supplement safety information and batch tested product list
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Bowtell, J., & Kelly, V. (2019). Fruit-derived polyphenol supplementation for athlete recovery and performance. Sports Med, 49, 3-23.
2. Somerville, V., Bringans, C., & Braakhuis, A. (2017). Polyphenols and performance: A systematic review and meta-analysis. Sports Med, 47, 1589-1599.
3. Bowtell, J., Kelly, V. (2019). Fruit-derived polyphenol supplementation for athlete recovery and performance. Sports Med, 49, S3-S23.
4. Kashi, D.S., Shabir, A., Da Boit, M., Bailey, S.J., Higgins, M.F. (2019). The efficacy of administering fruit-derived polyphenols to improve health biomarkers, exercise performance and related physiological responses. Nutrients, 11, 2389.
5. Vitale, K.C., Hueglin, S., Broad, E. (2017). Tart cherry juice and athletes: A literature review and commentary. Curr Sports Med Rep, 16, 230-239.
6. Cook, M.D., Willems, M.E. (2019). Dietary anthocyanins: A review of the exercise performance effects and related physiological responses. Int J Sport Nutr Exerc Metab. 29:, 322-30.
7. Kressler, J., Millard-Stafford, M., & Warren, G. L. (2011). Quercetin and endurance exercise capacity: a systematic review and meta-analysis. Med Sci Sports Exerc, 43: 2396-2404.
8. Somerville, V.S., Braakhuis, A.J., Hopkins, W.G. (2016). Effect of flavonoids on upper respiratory tract infections and immune function: A systematic review and meta-analysis. Adv Nutr, 7, 488-497.
9. Braakhuis, A. J., Somerville, V. X., & Hurst, R. D. (2020). The effect of New Zealand blackcurrant on sport performance and related biomarkers: a systematic review and meta-analysis. J Int Soc Sports Nutr, 17, 1-10.
10. Levers K, Dalton R, Galvan E, O’Connor A, Goodenough C, Simbo S, Mertens-Talcott SU, Rasmussen C, Greenwood M, Riechman S, Crouse S, Kreider RB. (2016). Effects of powdered Montmorency tart cherry supplementation on acute endurance exercise performance in aerobically trained individuals. J Int Soc Sports Nutr, 26, 13:22.
11. Howatson G, Bell PG, Tallent J, Middleton B, McHugh MP, Ellis J. (2012). Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. Eur J Nutr, 51(8), 909-16.
12. Ammar, A., Bailey, S.J., Chtourou, H., Trabelsi, K., Turki, M., Hökelmann, A., Souissi, N. (2018). Effects of pomegranate supplementation on exercise performance and post-exercise recovery in healthy adults: a systematic review. Br J Nutr, 120, 1201-16.

• Vit. C is a water-soluble antioxidant vitamin that acts as an electron donor for numerous biochemical reactions in the body. Vitamin C plays important roles as a cofactor for enzymes involved in collagen hydroxylation, plus carnitine and catecholamine biosynthesis. Vit. C also aids in iron absorption. A deficiency of Vit. C is rare given relatively low recommended dietary intake (45 mg per day) and wide distribution in fresh fruit and vegetables.
  • As an antioxidant, Vit. C reacts with potentially damaging reactive oxygen species (ROS) and reactive nitrogen species (RNS) and has beenshown to protect plasma lipids against oxidative damage.¹ Vit. C also strengthens the cellular antioxidant network by helping to maintain Vit. E and glutathione levels.^2-4
  • Vit. C is very labile and thus content in food varies according to season, transport, shelf life and storage time, cooking practices and chlorination of water. Cutting, bruising, heating and exposure to copper, iron or mildly alkaline conditions can destroy ascorbate. It can also be leached into water during cooking.⁵
• Vit. C may enhance immune function through effects on epithelial barriers, white blood cells and inflammatory mediators.6 Through enhancement of immune cell function, Vit. C may be able to prevent and treat respiratory and systemic infections.⁶ Vit. C supplements are promoted to reduce the duration and severity of colds, although the evidence supporting this is mixed:
  • Vit. C supplementation (200-2000 mg per day) has been found to reduce the duration of the common cold by 8% and reduce the severity of cold symptoms.⁷ Neither acute nor chronic Vit. C supplementation influences the incidence of upper respiratory tract infections.
  • Some studies in military personnel and school boarders have found a reduction in incidence of pneumonia by 80-100% with Vit. C supplementation⁸, although findings of these studies cannot be extrapolated to other groups.
• Vit. C may have benefits for athletes undertaking intense exercise. During exercise, our muscles produce increased amounts of ROS and RNS. Excess ROS and RNS can promote damage to proteins, lipids, and DNA, and potentially impair physical performance, recovery, and immune function. Vit. C supplements may act to neutralize some of the damaging effects of exercise-induced ROS and RNS, although studies report mixed findings on exercise-related outcomes:
  • A systematic review found that regular Vit. C supplementation (250-1000 mg per day) reduced the risk of the common cold by over 50% in athletes such as marathon runners and skiers who are exposed to short periods of extreme physical stress.7
  • Some evidence from randomized controlled trials indicate Vit. C supplementation (500-2000 mg per day) can prevent exercise-induced bronchoconstriction.⁹
  • Studies of effects of Vit. C supplementation on muscle function following a bout of intense fatiguing exercise have yielded mixed findings^10-15, drawing into question its use for recovery of muscle function.
  • There is compelling evidence to suggest chronic ingestion of single high dose antioxidants such as Vit. C (1000 mg per day for 8 weeks) can impede training adaptations¹⁶, yet when the same amount of Vit C is ingested via while food sources, performance may actually improve.¹⁷ Collectively this supports a food first approach to achieving Vit. C and other antioxidant nutrient needs, except in unique circumstances

• Vit. C is found naturally in a wide range of fruits and vegetables, including citrus fruits, berries, kiwifruit, tomatoes, broccoli, potatoes, capsicum, and sprouts. Vit. C food sources are presented in Table¹.
• Vit. C (as ascorbic acid and/or sodium ascorbate) is also widely available in oral supplement forms including capsules, tablets, powders or drops. Vit. C may also be intravenously infused if medically indicated. Oral Vit. C powder (as ascorbic acid) is white to off-white or light yellow in colour.
• On average, Australian adults consume approximately 110 mg Vit. C per day5, ~40% of which comes from vegetables, 19% from fruit and 27% from fruit and vegetable juices. Oral Vit. C supplements typically contain Vit. C in the range of 200 – 2000 mg per capsule or tablet.

• The integration of unprocessed, Vit. C rich foods into the daily meal plan is key to achieving not only daily Vit. C needs, but other important nutrients like fibre and phytochemicals.
• Only when directed by a sports dietitians or sports doctor, should an athlete consider acute Vit. C supplementation.
• A daily total dose of between 500-1000 mg supplemental Vit. C may be safe to consume acutely (during illness) to support immune health for most athletes undertaking intense exercise.

Table 1: Dietary sources of vitamin C

Possible impairment of exercise training adaptations

Some of the biological adaptations to training are stimulated by exercise-induced production of ROS and RNS. Antioxidant supplements that act to reduce ROS and RNS may therefore blunt these signals and make the training process less effective. Current uncertainty of evidence warrants an athlete discussing their training and performance goals with their coach and sports dietitian to manage the potential trade-off between possible acute immune-related benefits of Vit. C supplementation and possible impairments in training-induced adaptations. Achieving daily Vit. C intake goals via whole food sources should be a priority.

Side effects at higher doses

Gastrointestinal effects such as bloating and osmotic diarrhoea are the most common adverse effects associated with high doses of Vit. C (i.e. 2-6 g per day) given over a short period of time.¹⁹ However, these effects are attenuated through reduction of intake and adaptation to increased doses. International bodies have imposed a prudent upper limit of intake of 1000 mg Vit. C per day based on these side effects.²⁰

Increased risk of kidney stones or worsening kidney function

There is a concern that high dose Vit. C supplements might promote kidney stones. However, studies in humans using doses between 30 mg and 10 g per day have provided conflicting results^21,22 and it is unclear if Vit. C plays a role in kidney stone formation. Nonetheless, it might be prudent to limit intake to <1000 mg Vit. C per day in individuals who are known kidney stone formers.²³ High dose Vit. C is probably contraindicated in patients with existing hyperoxaluria and end stage renal disease.²²

Excess iron absorption in genetically prone individuals

Concerns have been raised in relation to use of high dose Vit. C supplements by individuals with genetic iron-overload disorders (e.g. haemochromatosis). Since Vit. C is a known enhancer of dietary iron absorption, it has been suggested that excessively high iron levels could damage the liver and heart and promote diabetes. Moderation (or omission) of supplemental Vit. C intake to no more than 500 mg per day is prudent for those individuals with genetic iron overload disorders.²⁴ On the contrary, co-ingestion of 50-100 mg Vit. C with non -haem iron sources significantly increases iron absorption, and thus may be an important to include fresh fruit and vegetables at most meals od the day amongst those with a history of impaired iron status.

Supplement safety information
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Frei, B. (1991). Ascorbic acid protects lipids in human plasma and low-density lipoprotein against oxidative damage. Am J Clin Nutr, 54(6 Suppl), 1113s-1118s.
2. Halpner, A. D., Handelman, G. J., Harris, J. M., Belmont, C. A., & Blumberg, J. B. (1998). Protection by vitamin C of loss of vitamin E in cultured rat hepatocytes. Arch Biochem Biophys, 359(2), 305-309.
3. Henning, S. M., Zhang, J. Z., McKee, R. W., Swendseid, M. E., & Jacob, R. A. (1991). Glutathione blood levels and other oxidant defense indices in men fed diets low in vitamin C. J Nutr, 121(12), 1969-1975.
4. Johnston, C. S., Meyer, C. G., & Srilakshmi, J. C. (1993). Vitamin C elevates red blood cell glutathione in healthy adults. Am J Clin Nutr, 58(1), 103-105.
5. Australian Bureau of Statistics (ABS). Australian Health Survey: Nutrition First Results - Foods and Nutrients, 2011-12. Canberra: ABS; 2014 May 9. Report No.: 4364.0.55.007. Available from: http://www.abs.gov.au/ausstats/abs@.nsf/mf/4364.0.55.007?OpenDocument
6. Carr, A. C., & Maggini, S. (2017). Vitamin C and Immune Function. Nutrients, 9(11), 1211.
7. Hemilä, H., & Chalker, E. (2013). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, 1.
8. Hemilä, H. 2004. Vitamin C supplementation and respiratory infections: a systematic review. Mil Med, 169(11), 920-925.
9. Hemilä, H. 2014. The effect of vitamin C on bronchoconstriction and respiratory symptoms caused by exercise: a review and statistical analysis. Allergy Asthma Clin Immunol, 10(1), 58.
10. Jakeman, P., & Maxwell, S. (1993). Effect of antioxidant vitamin supplementation on muscle function after eccentric exercise. Eur J Appl Physiol Occup Physiol, 67(5), 426-430.
11. Thompson, D., Williams, C., McGregor, S. J., Nicholas, C. W., McArdle, F., Jackson, M. J., & Powell, J. R. (2001). Prolonged vitamin C supplementation and recovery from demanding exercise. Int J Sport Nutr Exerc Metab, 11(4), 466-481.
12. Bryer, S. C., & Goldfarb, A. H. (2006). Effect of high dose vitamin C supplementation on muscle soreness, damage, function, and oxidative stress to eccentric exercise. Int J Sport Nutr Exerc Metab, 16(3), 270-280.
13. Connolly, D. A., Lauzon, C., Agnew, J., Dunn, M., & Reed, B. (2006). The effects of vitamin C supplementation on symptoms of delayed onset muscle soreness. J Sports Med Phys Fitness, 46(3), 462-467.
14. Thompson, D., Bailey, D. M., Hill, J., Hurst, T., Powell, J. R., & Williams, C. (2004). Prolonged vitamin C supplementation and recovery from eccentric exercise. Eur J Appl Physiol, 92(1-2), 133-138.
15. Close, G. L., Ashton, T., Cable, T., Doran, D., Holloway, C., McArdle, F., & MacLaren, D. P. (2006). Ascorbic acid supplementation does not attenuate post-exercise muscle soreness following muscle-damaging exercise but may delay the recovery process. Br J Nutr, 95(5), 976-981.
16. Gomez-Cabrera, M., Domenech, E., Romagnoli, M., Arduini, A., Borras, C., Pallardo, F., Sastre, J., Viña, J. (2008). Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance. Am J Clin Nutr, 87(1), 142-9.
17. Braakhuis AJ, Hopkins WG, Lowe TE. (2014). Effects of dietary antioxidants on training and performance in female runners. Eur J Sport Sci, 14(2), 160-8.
18. Padayatty, S., Katz, A., Wang, Y., Eck, P., Kwon, O., Lee, J.-H., . . . Levine, M. (2003). Vitamin C as an Antioxidant: Evaluation of Its Role in Disease Prevention. J Am Coll Nutr, 22, 18-35.
19. Naidu, K. A. (2003). Vitamin C in human health and disease is still a mystery? An overview. Nutr J, 2, 7.
20. National Health and Medical Research Council (NHMRC), Australian Government Department of Health and Ageing, New Zealand Ministry of Health. Nutrient Reference Values for Australia and New Zealand.  Canberra: National Health and Medical Research Council; 2006.
21. Massey, L. (2005). Safety of vitamin C. Am J Clin Nutr, 82(2).
22. Robitaille, L., Mamer, O. A., Miller, W. H., Jr., Levine, M., Assouline, S., Melnychuk, D., . . . Hoffer, L. J. (2009). Oxalic acid excretion after intravenous ascorbic acid administration. Metabolism, 58(2), 263-269.
23. Traxer, O., Huet, B., Poindexter, J., Pak, C. Y., & Pearle, M. S. (2003). Effect of ascorbic acid consumption on urinary stone risk factors. J Urol, 170 (2 Pt 1), 397-401.
24. Barton, J. C., McDonnell, S. M., Adams, P. C., Brissot, P., Powell, L. W., Edwards, C. Q., . . . Kowdley, K. V. (1998). Management of hemochromatosis. Hemochromatosis Management Working Group. Ann Intern Med, 129(11), 932-939.

• The use of menthol, when co-ingested with or incorporated into a gel or cold/iced-slurry beverage, may be useful during exercise to facilitate a perception of feeling ‘cool’.
• Menthol mimics the cold stimulation of thermosensitive neurons (Transient receptor potential melastatin 8; TRPM-8) when applied to mucous membranes.¹
  • The sensory impact of L-menthol is directly related to the thickness of the skin, density of afferents, concentration of menthol, repetition and length of time of exposure.²
• The internal application of menthol (via mouth rinse or ingestion) is potentially ergogenic when performing endurance activities (>2.5 min) in hot environments by ameliorating athlete’s perception of heat stress by reliably improving thermal sensation, and to a lesser extent, thermal comfort and ratings of perceived exertion in the absence of any change in body (i.e., core and skin) temperature.³
  • Further downstream improvements of internal menthol application may include improvements in nasal patency⁴, alterations in blood flow⁵ and attenuation of thirst.⁴

• In its raw form (pharmaceutical grade; 100% pure), menthol is a stable solid white crystal.
  • Menthol is a natural compound; the (-) isomer is derived from Mentha species (i.e., peppermint, corn mint) and is associated with a characteristic ‘minty’ aroma, taste and cooling sensation⁶.
  • Menthol is widely used as a food ingredient to flavour confectionary, oral hygiene and medicinal products, and is unlikely to be detrimental o health and/or performance unless recommended protocols regarding frequency and concentration are exceeded.
  • Menthol is commercially available through food ingredient (e.g., Melbourne Food Depot) and chemical/laboratory materials supply ompanies (e.g., Sigma Aldrich).
• Currently there is only one commercially available Menthol-containing product range marketed specifically as a sports product (Turbo+, Science in Sport), which is targeted for use during indoor training. However, it has limited availability for purchase in Australia, and contains other ingredients (22 g Carbohydrate, 0.01% active Menthol, 150 mg Caffeine, 1.5 g Beta-alanine, 1.5 g L-Carnitine) which may limit its use to specific sports situations.
• Based on the current understanding of the potential benefits of L-Menthol, individuals may wish to experiment with:
  • Ingesting or mouth rinsing a menthol-containing food-grade product (i.e., confectionary such as Fisherman’s Friend - Original).

• There is no clear consensus on safe and effective menthol use for athletes, practitioners or researchers³. Best practice protocols are yet to be established.
  • Current guidelines should be followed, which proposes a mouth rinse or beverage containing L-Menthol (0.1 – 0.5 g of crushed L-menthol crystals in 1 L water, equivalent concentration of 0.01 – 0.05% Menthol).⁷
• L-Menthol supplementation should only be considered and trialled in collaboration with an accredited sport scientist and/or sports dietitian. Individuals should extensively trial intended uses of menthol and pacing strategies under similar environmental conditions prior to implementing in competition, which may include the following strategies:
  • Repeated internal application every 5-10 min during exercise.
  • Optimising the potential sensory benefits, consider use at strategic time points (e.g., towards the end of a prolonged endurance event).
  • The cooling sensation may be heightened if menthol is co-ingested with or incorporated into cold or ice slurry beverages.⁸

The potential risks of oral menthol application in the heat are not yet fully understood. The following risks have, so far, been identified:

Table 1: Potential Risks of Internal Menthol Use

Limitations to the current evidence supporting menthol use

High-Performance Environment

• Studies among elite athletes, particularly in events that are representative of real-world performances and conditions (e.g., the degree of thermal discomfort tolerated, motivation for success/resist fatigue) is of high priority.

Sex

• L-menthol research has largely been conducted on male cohorts who are recreationally active or trained. It is not known whether the subtle alterations in sub-elite populations will translate to measurable outcomes for elite athlete in the field.³
• Research on female participants is to be encouraged because of identified sex-differences in olfaction and trigeminal sensitivity.¹⁰

Sports/Activities

• More research is warranted on the effects of L-Menthol, on performance of intermittent, dynamic and explosive activities, fine motor movements, or team-based competitive sports due to insufficient research in the field.³

Safety

• To our knowledge, there are no recorded instances of heat-related illness in experiments involving the internal application of L-menthol. Such experiments are ethically bound by strict withdrawal criteria and therefore, careful thermal monitoring during athletic events in less-controlled environments is necessary.

Individual Responses

• Inter-individual difference in response to L-menthol mouth rinsing may be distinguished by the calculation of an individual’s menthol sensitivity index.¹¹
• A clear dose-response has yet to be identified. Individual approaches are warranted above pursuing a ‘more is better’ approach.

Diminishing Returns

• Further understanding of single or repeated mouth rinsing and the reasons for habituation (i.e., diminished response to the repeated application of menthol dose) need to be clarified.

Sports Dietitians Australia
Position Statement: Nutrition for Exercise in Hot Environments

Supplement safety information
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

Material Safety Data Sheet (MSDS) information
www.merckmillipore.com/AU/en/product/msds/MDA_CHEM-105995

1. McKemy, D. TRPM8: The Cold and Menthol Receptor. (2007) In W.B. Liedtke, S. Heller (Eds.) FL, USA: Boca Raton: CRC Press/Taylor & Francis.
2. Stevens, Ross & Vogel. (2020). Development of a menthol energy gel for endurance athletes. IJSNEM, 27, 1-6.
3. Barwood, Gibson, Gillis et al. (2020). Menthol as an Ergogenic Aid for the Tokyo 2021 Olympic Games: An Expert-Led Consensus Statement Using the Modified Delphi Method. Sports Medicine, 50, 1709-1727.
4. Eccles, R. (200). Role of cold receptors and menthol in thirst, the drive to breathe and arousal. Appetite, 34(1), 29-35.
5. Kashimaa, H., Hayashiab, N. (2013). Facial skin blood flow responses to irritant stimuli in the oral cavity. Auton Neurosci Basic Clin, 174(1– 2), 61–5.
6. Eccles, R. (1994). Menthol and related cooling compounds. J Pharmacy and Pharmacology, 46(8), 618-630.
7. Stevens, C. J., & Best, R. (2017). Menthol: A fresh ergogenic aid for athletic performance. Sports Medicine, 47(6), 1035-1042.
8. Riera, F., Trong, T.T., Sinnapah, S., Hue, O. (2014). Physical and perceptual cooling with beverages to increase cycle performance in a tropical climate. PLoS One, 9(8).
9. Kumar, Baitha, Aggarwal, Jamshed. (2016). A fatal case of menthol poisoning. Int J Appl Basic Med Res, 6(2), 137.
10. Hummell, T., Livermore, A. (2002). Intranasal chemosensory function of the trigeminal nerve and aspects of its relation to olfaction. Int Arch Occ Environ Health, 75(5), 305-13.
11. Lee, Kakao, Bakri & Tochihara. (2012). Body regional influences of L-Menthol application on the alleviation of heat strain while wearing firefighter’s protective clothing. Eur J App Physiol, 112(6), 2171-83.

1. Barwood M, Corbett J, White D, et al. (2012). Early change in thermal perception is not a driver of anticipatory exercise pacing in the heat. Br J Sports Med, 46(13), 936–42.
2. Best R, Payton S, Spears I, et al. (2018). Topical and Ingested Cooling Methodologies for Endurance Exercise Performance in the Heat. Sports (Basel), 6(1), 2.
3. Flood T. (2018). Menthol Use for Performance in Hot Environments. Curr Sports Med Rep, 17(4), 135-139.
4. Flood, Waldron, Jeffries. (2017). Oral L-menthol reduces thermal sensation, increases work-rate and extends time to exhaustion, in the heat at a fixed rating of perceived exertion. Eur J Appl Physiol, 117(7), 1501-1512.
5. Galeotti N, Di Cesare Mannelli L, Mazzanti G, Bartolini A, Ghelardini C. Neurosci Lett. (2002). Menthol: a natural analgesic compound. Neurosci, 322(3), 145-8.
6. Jeffries O, Waldron M. (2019). The effects of menthol on exercise performance and thermal sensation: A meta-analysis. J Sci Med Sport, 22(6), 707-715.
7. Le Meur, Y. (2020) Beating the heat with menthol. YLMSportScience. ylmsportscience.com/2020/12/07/beating-heat-with-menthol.
8. Mundel, T., & Jones, D. A. (2010). The effects of swilling an L(-)-menthol solution during exercise in the heat. European Journal of Applied
   Physiology, 109(1), 59-65.
9. Stevens & Dascombe. (2015). The reliability and validity of protocols for the assessment of endurance performance: an updated review. Meas Phys Edu Exerc Sci, 19(4), 177-85.
10. Stevens, C. J., Thoseby, B., Sculley, D. V., Callister, R., Taylor, L., & Dascombe, B. J. (2016). Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice slurry ingestion. Scandinavian Journal of Medicine and Science in Sports, 26(10), 1209-1216.
11. Stevens C, Bennett K, Sculley D, et al. (2017). A comparison of mixed-method cooling interventions on preloaded running performance in the heat. J Strength Cond Res, 31(3), 620-29.

• TRP channels are a group of ion channels located on the plasma membrane of numerous cell types which are mediators of a variety of sensations, including pain, temperature, taste, pressure and stretch. Some of these channels are activated by compounds naturally found in food.
• TRP channel agonists taken as supplements, are a range of products, typically in liquid form, that are designed to prevent or reduce the severity of Exercise Associated Muscle Cramping (EAMC) during or after exercise. Commercial products that provide one or multiple TRP channel agonists as ingredients include pickle juice, and a commercial ‘shot’ that combines lime juice, capsaicin, ginger and cinnamon.
• The active ingredients are food components, that when ingested can activate TRP vanilloid 1 (TRPV1) and TRP Ankyrin 1 (TRPA1) channels in the mouth and upper gastrointestinal tract.¹ These channels are involved in the differentiation of sensory aspects of food (i.e. salty taste and pungency) and can be activated by compounds in food that have these specific properties.³ TRPV1 can be activated by capsaicin, the compound in chillies that give them the spicy flavour (especially in an acidic environment), while TRPA1 is activated by components found in wasabi, mustard or horseradish, garlic, cinnamon, and to a lesser extent onion, garlic, cumin, anise and acidic foods.^2,3
• Activation of TRPV1 and TRPA1 channels is suggested to alter neurological activity, and through the triggering of sensory neurons may reduce the excitability of α-motor neurons in the spinal cord, which influence skeletal muscle contraction.¹ This in turn is theorised to increase the neurological threshold for muscle cramping or reduce the frequency or severity of muscle cramps during exercise.

Current products include:

• Pickle juice, typically sold commercially in beverage form. The main active ingredient in this case is vinegar, although the very high sodium content has also been suggested to play a role as an active ingredient. Interestingly, commercial pickle juice beverages have usually never been in contact with a pickle – instead, it is a replica of the pickling brine that is used, including flavouring with dill as occurs when pickling cucumbers.
• Energy gels which contain vinegar or capsicum annum that are marketed specifically for the reduction in cramping.
• A 50 mL commercial “shot” containing a combination of lime juice, capsaicin, ginger and cinnamon.

There are currently no established guidelines or recommendations for the dose of TRP channel agonists required in order to prevent or treat EAMC, nor is the quantity of these components of a product typically labelled. Furthermore, research on pickle juice does not report the specific dose of active ingredients, rather, the total dose of supplement is reported – 1mL/kg of pickle juice.⁴ The 50 mL dose of the commercial shot is listed in research papers as providing up to 38 mg capsicum, up to 500 mg cinnamon, and up to 750 mg ginger.¹

• Both pickle juice and other commercial TRP receptor agonists are typically consumed when the athlete is concerned about, or has experienced, EAMC. It has been suggested, but not verified through a research protocol, that mouth rinsing would be comparable to swallowing the supplement, as TRP channels exist within the mouth and upper oesophagus, and this is where the product is designed to have an effect neurologically.
• Study protocols vary, using either ingestion of the supplement immediately (~15 min) before exercise, and/or immediately at the onset of EAMC.

Validity of cramping research models to real-world sporting scenarios

The vast majority of research on TRP channel agonists is conducted in a laboratory environment, using an electrically stimulated cramping model in isolated muscles or small muscle groups to measure the “threshold frequency” for cramping – that is, how easily a muscle cramps in response to electrical stimulation. Whilst the threshold frequency appears related to an athlete’s real-world susceptibility to cramping, the results of these laboratory studies have yet to be replicated in a real-world sporting context.

Unnecessary expense and lack of scientific consensus on prescription

There is currently no consensus on the optimal dose of TRP channel agonists, whether some (e.g. vinegar) are more effective than others (e.g. cinnamon), whether combining multiple TRP channel agonists provides an additive or synergistic effect, the optimal timing of ingestion, and whether mouth rinsing is equivalent to swallowing the supplement.

Tolerance of extremely pungent flavours

TRP channel agonists are, by their very nature, strong and pungent flavours, which may be particularly overwhelming during exercise in hot environments. Athletes are strongly advised to always try these products in training that simulates race conditions (i.e. exercise intensity and climate as similar as possible) before attempting to use them in a race scenario.

Gastrointestinal disturbance from ingestion of highly concentration sodium solutions

Pickle juice products in particular are extremely high in sodium, increasing the risk of gastrointestinal discomfort, nausea and/or vomiting. However, research suggests that in the small quantities consumed (~50-80 mL, or around 500-900 mg sodium at a time), there is unlikely to be any observable change in plasma sodium or osmolality⁵, or gastrointestinal symptoms.

Lack of understanding on the causes of EAMC and thus most appropriate interventions

Exercise Associated Muscle Cramping is poorly understood due to the difficult nature of studying the phenomenon. However, current consensus suggests that EAMC is likely a syndrome, with multiple and diverse risk factors increasing an individual’s susceptibility to cramping⁶, which is the ultimate outcome. Unlike other syndromes that occur in athletes (e.g. exercise induced gastrointestinal syndrome), currently there is no clear mechanistic pathway to explain the link from risk factors to cramping outcomes, and therefore treatments are generally not targeted towards a specific causal pathway. Because of this, it is not known if TRP channel agonists will be effective for all athletes who experience EAMC, or whether it is only useful in athletes whose cramping has a more specific causal pathway.

Gatorade Sport Science Institute
www.gssiweb.org/docs/default-source/sse-docs/maughan_sse_200_final.pdf?sfvrsn=2

Supplement safety information and batch tested product list
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Craighead DH et al. (2017). Ingestion of TRP channel agonists attenuates exercise-induced muscle cramps. Muscle Nerve, 56(3), 379–385.
2. Legrand C et al. (2010). New natural agonists of the transient receptor potential Ankyrin 1 (TRPA1) channel. Sci Rep, 10(1), 11238.
3. Roper SD. (2014). TRPs in Taste and Chemesthesis. Handb Exp Pharmacol, 223, 827–871.
4. Miller KC et al. (2009). Reflex Inhibition of Electrically Induced Muscle Cramps in Hypohydrated Humans. Med Sci Sports Exer. 2009; 42(5):953-961.
5. Miller KC et al. (2009). Electrolyte and Plasma Changes After Ingestion of Pickle Juice, Water, and a Common Carbohydrate-Electrolyte Solution. J Athl Train, 44(5), 454–461.
6. Maughan RJ & Shirreffs SM. (2019). Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining. Sports Med, 49(Suppl 2), 115-124.

• Quinine is a bitter alkaloid sourced from the bark of the cinchona tree1 and has a long history of use in traditional medicine such as a treatment for malaria², where doses of 1 g of quinine sulphate were administered before the acute phase.³
• Quinine carries a strong bitter taste⁴ and is used in tonic water as a flavouring agent.¹ Its concentration in commercial beverages varies greatly and such products typically lack nutritional information detailing the amount of quinine used. The concentration of quinine in tonic water is much lower than that used for medical purposes.
• Quinine is one of the latest emerging acute nutritional strategies that purportedly activate brain areas to reduce perception of effort and subsequent pacing decisions, in both research and practical settings.⁵
• Ingestion of Quinine activates the bitter taste receptors in the oral cavity and upper gastrointestinal tract to increase corticomotor excitability and stimulate neural excitability.⁴ Changes in the autonomic nervous system (ANS)^6,7 provide a potential mechanism to enhance performance in high effort, short duration activities.
• Unlike the case for carbohydrate mouth rinsing, the quinine solution needs to be swallowed for it to prove effective⁴ and to ensure that it has contact with specific receptors that are concentrated in the back of the mouth and throat.
• Benefits of quinine ingestion as a sensory-driven tastant include increased 30 second cycling sprint performance by 2.5-4%⁸ and increased cycling performance (~6%) during initial stages of a 3 to 4-minute cycling effort.⁹
• Since the effects of quinine ingestion are seen immediately after the ingestion of quinine, the ergogenic effect has been attributed to central activation by afferent taste.
• To date, studies that have reported benefits of quinine ingestion have involved exercise protocols undertaken on cycle ergometers. It is unclear if this translates to real world cycling (e.g. track cycling) and whether other sprint events in running or swimming would benefit from pre-event quinine ingestion.
• It is unclear whether other factors might inhibit or diminish sensory-driven pathways when ingesting quinine. For example, bitter tasting medications are often masked by manipulations involving salt.¹⁰ Therefore, it might be possible to counter-act an unpleasant and persistent bitter taste after the event by ingesting a salty snack. However, whether salt intake prior to or around the pre-event quinine ingestion interferes with any ergogenic effect is unknown.
• It is also relevant to explore ways to amplify sensitivity to the bitter taste prior to ingesting quinine to magnify performance benefits without needing to increase the actual dose.

The manufacturer’s guidelines should be followed in regards to the shelf-life of the quinine powder (Quinine Hydrochloride Dihydrate). Once the solution is prepared it should be consumed as soon as possible given the lack of information about the shelf-life and biological effectiveness.

• A single dose of quinine solution is prepared by mixing 0.02 g of Quinine Hydrochloride Dihydrate in 25 ml of deionised water (or 0.08 g per 100ml of deionised water). Such a solution is considered safe to use. However, quinine powder (Quinine Hydrochloride Dihydrate) is considered hazardous and requires careful handling.
• It is necessary to swirl the quinine solution in the mouth and then swallow it to achieve a beneficial effect.¹¹
• Such a protocol (10-20 seconds prior to the sprint) has been found to improve a maximal 30 second cycling effort⁸ and the initial 80 seconds of a 3 to 4-minute cycling time-trial.⁹
• However, quinine ingestion during the last 90 second of a 4-minute maximal cycling effort has failed to improve performance.¹²
• Ingesting the directed single dose of quinine solution triggers an extremely bitter sensation in the mouth, which can be counteracted, postevent and after benefitting from the ergogenic effect of the tastant, by ingesting a salty snack (e.g. Salt and Balsamic vinegar flavoured rice cakes) or equivalent.

Limited evidence for dose-response

• No adverse effects have been reported when quinine is used in low doses (0.02 g of quinine in a 25 ml solution) prior or during exercise, and a single dose of quinine solution as described above is considered safe for use. It is unclear if concentrations higher than 2mM of quinine would trigger a higher sensory-driven response for even greater performance benefits – or, in contrast to this, induce detrimental effects.
• Currently, there is insufficient evidence to consider individual responsiveness to quinine ingestion in the sporting setting. However, ingestion of strong-tasting nutrients alongside or prior to quinine ingestion could interfere with its performance effects if it counteracts the bitter taste or sensory response triggered.

Careful handling required

• Quinine powder (Quinine Hydrochloride Dihydrate, S1125, Sigma-Aldrich Pty Ltd, Australia) is considered a hazardous chemical and requires careful handling when preparing the solution.
• Although not classed as a dangerous chemical, inappropriate handling or accidental inhaling of quinine powder can cause acute oral toxicity, impaired respiration and skin sensitisation.

Evidence for benefits still lacks certainty

Benefits might be specific to certain scenarios and short-term duration of effort. Further research is needed before more information can be provided around specific protocols, including targeted sprint events, potential uses in training and different modes of ingestion (e.g. gels or solid forms) that might be more practical to achieve in competition scenarios.

Supplement safety information and batch tested product list
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Brasic, J. R. (1999). Should people with nocturnal leg cramps drink tonic water and bitter lemon? PR, 84(2), 355-367.
2. Permin, H., Norn, S., Kruse, E., & Kruse, P. R. (2016). On the history of Cinchona bark in the treatment of Malaria. DMA, 44, 9-30.
3. Marchoux, E. (1933). Les traitements du paludisme [Treatments of malaria]. Malaria Commission CH/Malaria/193.
4. Gam, S., Guelfi, K. J., Hammond, G., & Fournier, P. A. (2015a). Mouth rinsing and ingestion of a bitter-tasting solution increases corticomotor excitability in male competitive cyclists. EJAP, 115(10), 2199-2204.
5. Best, R., McDonald, K., Hurst, P., & Pickering, C. (2021). Can taste be ergogenic? EJN, 1, 45-54.
6. Kelley, A. E., Baldo, B. A., Pratt, W. E., & Will, M. J. (2005). Corticostriatal-hypothalamic circuitry and food motivation: integration of energy, action and reward. PB, 86(5), 773-795.
7. Robin, O., Rousmans, S., Dittmar, A., & Vernet-Maury, E. (2003). Gender influence on emotional responses to primary tastes. PB, 78(3), 385-393.
8. Gam, S., Guelfi, K. J., & Fournier, P. A. (2014). Mouth rinsing and ingesting a bitter solution improves sprint cycling performance. MSSE, 46(8), 1648-1657.
9. Etxebarria, N., Ross, M. L., Clark, B., & Burke, L. M. (2019). Ingesting a Bitter Solution: The Sweet Touch to Increasing Short-Term Cycling
   Performance. IJSPP, 14(6), 727-732.
10. Rahman, Z., Siddiqui, A., & Khan, M. A. (2013). Orally disintegrating tablet of novel salt of antiepileptic drug: formulation strategy and evaluation. EJPB, 85(3 Pt B), 1300-1309.
11. Gam, S., Tan, M., Guelfi, K. J., & Fournier, P. A. (2015b). Mouth rinsing with a bitter solution without ingestion does not improve sprint cyclingperformance. EJAP, 115(1), 129-138.
12. Etxebarria, N., Clark, B., Ross, M., Hui, T., Goecke, R., Rattray, B., & Burke, L. (2020). Quinine ingestion during the latter stages of a 3000 m time trial fails to improve cycling performance. IJSNEM, ahead of print.

• Collagen is the most abundant protein within the body, residing in the extracellular matrix (ECM) of several tissues including skin, bone, ligaments and tendons.¹ It is unique in that it forms as a triple helical structure, resulting in a rigid and durable tissue, which provides structure and support to the body, as well as playing a role in locomotion.² To date, there are 28 different types of collagen known which are composed of polypeptide chains.³
• Within bone, muscle and connective tissue, Type 1 collagen predominates, consisting of non-essential amino acids (NEAAs) including glycine, proline, hydroxyproline and hydroxylysine.⁴ The specific role of each of these AAs and/or peptides after the consumption of collagen is still being explored.

• Plasma levels of glycine decline post exercise, potentially due to increased utilisation. This suggests an increased need for glycine while collagen synthesis is elevated post exercise.⁵ It has been hypothesized that under circumstances of high demand such as a heavy training stimulus, dietary collagen may be of potential benefit.
• The addition of ascorbic acid and proline to cell culture growth media), results in an increased collagen content and improvement to mechanical properties⁶. This suggests both are important nutrients for the synthesis of collagen in connective tissue. However, whether intake beyond dietary sufficiency is required in vivo is yet to be determined.
  • Although AAs derived from the consumption of diary protein (casein), including proline are incorporated into intramuscular connective tissue after a bout of resistance training, this does not result in a further increase of intramuscular connective tissue protein synthesis rates, compared to when a placebo is consumed. This may be due to the low glycine content of casein compared to collagen proteins.⁵
  • Inflammation results in the disorganisation of collagen fibrils in the ECM, and has been proposed to lead to conditions such as tendinopathy.⁶ Glycine has been shown to inhibit inflammatory cell activation⁷, and therefore may be able to exert a beneficial effect in inflammatory conditions. The administration of glycine results in an improvement in the biochemical and biomechanical properties of an inflamed rat tendon⁸, and restores the anabolic response of muscle tissue to leucine under acute inflammatory conditions.⁹
  • Plasma di and tri peptide amino acids of hydroxyproline available post the ingestion of collagen proteins appear to trigger a range of signalling responses in the human body. How this translates into functional outcomes of enhanced collagen synthesis or improved connective tissue health in vivo is still unclear.¹⁰

• Hydrolysed collagen is a form of collagen that has undergone enzymatic hydrolysis to reduce its’ gelling properties to enable it to be easily mixed with water, and ingested.¹¹ Meanwhile, specific collagen peptide formulations have been developed to optimise the amount of di and tri AA peptides of hydroxyproline with different molecular weights. Such formulations are claimed to have increased bioavailability,and exert additional biological functions specific to the target tissues.^12-15 However, it should be noted that there does not appear to be significant differences in the bioavailability of key AAs after the consumption of different forms of collagen.¹⁶
• The consumption of collagen results in a transient increase of circulating NEAA within the blood, peaking between 40-60 minutes after consumption.^{16, 17} However, there appears to be some individual variability with the availability of AAs after the consumption of collagen protein. Variability in amino acid appearance between subjects and interventions likely influenced by body weight, and possible polymorphisms of transporters and enzymes, which is potentially linked to habitual dietary intake of collagen sources.¹⁸ Further research is required to determine these individual factors.

• Although bone collagen is responsive to feeding in the absence of exercise¹⁹, collagen in musculoskeletal tissue is non-responsive to feeding in the absence of exercise.²⁰ Exercise is necessary to “switch-on” synthetic machinery in muscle and connective tissue ²¹, and may also increase the delivery of specific AAs when their availability is increased (i.e. after the consumption of protein sources), particularly in dense connective tissues which are otherwise poorly vascularised.²² Further, as it has been shown that proline is integrated into muscle collagen when dairy protein is ingested post exercise⁵, it is possible that protein to support muscle recovery/repair may be better consumed post exercise.
• A recent study has shown that serum obtained from individuals after the consumption of dietary collagen (gelatin) resulted in an increased collagen content, and improved tissue mechanics of an engineered ligament. Meanwhile, an in vitro arm of the same study illustrated an increased availability of collagen specific AAs within the blood, and an increase in a blood marker of collagen synthesis (Procollagen type I Intact N-Terminal) after collagen was consumed 1h prior to a 6-minute skipping exercise.¹⁷ This suggests that the increased availability of collagen specific AAs and/or peptides in combination with exercise may result in an increased collagen synthesis within connective tissue.
• Although gelatin (a partially hydrolysed form of collagen utilised predominantly in food manufacturing) has been utilised in formative research exploring the impact of collagen intake on the synthesis of collagen, it is not considered to be palatable in its raw form to consume mixed in water due to collagens gelling properties, and therefore alternative formulations may be better tolerated. Incorporation of gelatin into food sources or forms should not influence its AA availability.

• Although in vivo research remains limited, it has been suggested that collagen supplementation may assist in the prevention and/or treatment of muscle, cartilage, connective and bone tissue injury and/or degenerative disorders.²³ A recent case study has shown that the combination of a rehabilitation protocol, including exercise and supplemental collagen protein may help hastened return to play.²⁴ Meanwhile, collagen specific peptides in conjunction with calf-strengthening exercises has been shown to increase functionality and reduce pain during tendinopathy.¹⁴ Other investigations have shown a reduction in subjective joint pain²⁵, plus decreased inflammation and muscle damage after strenuous exercise.²⁶
• Collectively, collagen supplementation, and/or the increased availability of AA which predominate in collagen may be beneficial for both the prevention and treatment of injury and degenerative bone and connective tissue disorders. However, the research remains within its’ infancy and more long-term studies are required to determine optimal doses, formulations and contra-indications for use. Thus, the use of collagen as part of an injury-prevention or management protocol should be considered carefully and should be used as an adjunct, not a replacement for traditional well-established processes.

• Hydrolysed collagen and collagen peptide formulas are available in the form of pills or powder, and can be derived from porcine, bovine or marine animals. The differences in the AA content of various animal and human collagen sources are presented in Table 1. Recent research has shown there is no significant difference in plasma availability of key AAs after the consumption of various collagen protein sources.¹⁶ Therefore, the source of collagen is unlikely to influence its’ effectiveness.
• Collagen in the form of gelatin is considered as a food product, and therefore, does not require batch-testing for use in athletes., Where access and/or budget is a consideration, gelatin may be a preferential option, especially if made into more palatable jellies or jubes.
• Some collagen formulations include ascorbic acid, due to its role as a cofactor in collagen synthesis.¹⁷ However, whether there is benefit beyond dietary sufficiency of ascorbic acid for collagen synthesis remains to be determined.
• Unfortunately, Australian food databases do not contain information on the collagen content of foodstuffs (measured as hydroxyproline), and therefore, it is not possible to determine collagen intake through food sources. Further, research has indicated that the AA content of collagen in bone broth, is too variable to use as a therapeutic source of collagen.²⁷

Table 1: Amino acid composition of the 5 major mammalian collagens and gelatin

Amounts given in grams per 100 grams of dry ash-free Protein. Adapted from.²⁸

• Although recent research utilised 15 grams of gelatin, this was due to the requirement to blind participants from the intervention. Other studies have shown an increased availability of AAs after the intake of up to 20-25 grams of collagen, Consequentially a minimum of 20 grams is likely optimal for increased AA availability around exercise in a timely manner16, ²⁹. It is possible that similar to other types of protein, a dose response relationship exists, however, this requires further research.
• Although more research is required to confirm the use of hydrolysed collagen and/or specific collagen peptide formulas for a range of scenarios and/or target tissues, it may be beneficial in the following situations as part of an overall injury management and/or prevention plan (in conjunction to well established methods):
• As mentioned, Vitamin C (ascorbic acid) is important as a cofactor in collagen synthesis, so the diet must be sufficient in Vit C.

Consumed daily:

• In conjunction with specific exercise to help pain management for inflammatory conditions such as tendinitis.
• To help reduce activity-related joint pain.
• For the treatment/prevention of degenerative diseases, such as osteoarthritis.
• To assist in bone strength in order to reduce fracture risk.

Consumed 40-60 minutes prior to exercise to:

• Help to support collagen turnover in connective tissue by providing an increased availability of AAs during periods of increased turnover, particularly when the body is unable to keep up with demand and/or when total protein intake is suboptimal, such as during a high training stimulus.
• Help support tissue integrity for those with previous connective tissue injury.
• Support the repair of various tissues, including bone, skin and ligaments/tendons during rehabilitation.

Consumed immediately post exercise in order to:

• Support the repair/recovery of muscle tissue, and potentially reduce delayed onset muscle soreness.

There is insufficient evidence to support the use of vegetarian/vegan alternatives

Collagen protein is animal-derived and therefore may not be appropriate for vegetarian/vegan athletes. Although there are vegan/vegetarian products available that are claimed to mimic animal sources of collagen, if peptides specific to animal proteins are proved to have specific biological activity, then vegetarian/vegan options may be viewed as less effective. More work is required to determine the AA availability and effectiveness of vegan collagen alternatives.

Potential individual variability of availability of AAs that may support collagen synthesis

As per any supplement, an individual approach should be considered. The individual availability of AAs proposed to increase collagen synthesis may be impacted by the following: habitual intake of protein, particularly collagenous proteins which may lead to differences in baseline AAs availability and/or reduced capacity to digest specific AA; training load in which the requirement of AAs such as glycine are conditionally increased; an individual’s body mass, leading to increased utilisation; the use of AAs in other processes such as bone remodelling.

Addition of ascorbic acid and its’ impact on interference with physiological adaptation

Chronic Vitamin C supplementation may impair physiological adaptation (see Vitamin C). Adequacy of dietary derived Vitamin C should be confirmed.

Religions requiring Halaal products

Halal certified collagen protein supplements are commercially available.

Gatorade Sports Science Institute
www.gssiweb.org

Supplement safety information
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Kadler, K., Holmes, D., Trotter, J., & Chapman, J. (1996). Collagen fibril formation. Biochem J, 316 ( Pt 1), 1-11.
2. Myllyharju, J., & Kivirikko, K. I. (2009). Collagens and collagen-related diseases. Annals of Medicine, 33(1), 7-21.
3. Shoulders, M. D., & Raines, R. T. (2009). Collagen structure and stability. Annu Rev Biochem, 78, 929-958.
4. Li, P., & Wu, G. (2018). Roles of dietary glycine, proline, and hydroxyproline in collagen synthesis and animal growth. Amino Acids, 50(1), 29-38.
5. Trommelen, J., Holwerda, A. M., Senden, J. M., Goessens, J. P. B., J, V. A. N. K., Gijsen, A. P., . . . LJC, V. A. N. L. (2020). Casein Ingestion Does Not Increase Muscle Connective Tissue Protein Synthesis Rates. Med Sci Sports Exerc, 52(9), 1983-1991.
6. Paxton, J. Z., Grover, L. M., & Baar, K. (2010). Engineering an in vitro model of a functional ligament from bone to bone. Tissue Eng Part A, 16(11), 3515-3525.
7. Trommelen, J., Holwerda, A. M., Senden, J. M., Goessens, J. P. B., J, V. A. N. K., Gijsen, A. P., . . . LJC, V. A. N. L. (2020). Casein Ingestion Does Not Increase Muscle Connective Tissue Protein Synthesis Rates. Med Sci Sports Exerc, 52(9), 1983-1991.
8. Dunstan, R. H., Macdonald, M. M., Murphy, G. R., Thorn, B., & Roberts, T. K. (2019). Modelling of protein turnover provides insight for metabolic demands on those specific amino acids utilised at disproportionately faster rates than other amino acids. Amino Acids, 51(6), 945-959.
9. Lipman, K., Wang, C., Ting, K., Soo, C., & Zheng, Z. (2018). Tendinopathy: injury, repair, and current exploration. Drug Des Devel Ther, 12, 591-603.
10. Zhong, Z., Wheeler, M. D., Li, X., Froh, M., Schemmer, P., Yin, M., . . . Lemasters, J. J. (2003). L-Glycine: a novel antiinflammatory,
    immunomodulatory, and cytoprotective agent. Curr Opin Clin Nutr Metab Care, 6(2), 229-240.
11. Vieira, C. P., De Oliveira, L. P., Da Re Guerra, F., Dos Santos De Almeida, M., Marcondes, M. C., & Pimentel, E. R. (2015). Glycine improves biochemical and biomechanical properties following inflammation of the achilles tendon. Anat Rec (Hoboken), 298(3), 538-545.
12. Ham, D. J., Caldow, M. K., Chhen, V., Chee, A., Wang, X., Proud, C. G., . . . Koopman, R. (2016). Glycine restores the anabolic response to leucine in a mouse model of acute inflammation. Am J Physiol Endocrinol Metab, 310(11), E970-981.
13. Oertzen-Hagemann, V., Kirmse, M., Eggers, B., Pfeiffer, K., Marcus, K., de Marees, M., & Platen, P. (2019). Effects of 12 Weeks of Hypertrophy Resistance Exercise Training Combined with Collagen Peptide Supplementation on the Skeletal Muscle Proteome in Recreationally Active Men. Nutrients, 11(5).
14. Leon-Lopez, A., Morales-Penaloza, A., Martinez-Juarez, V. M., Vargas-Torres, A., Zeugolis, D. I., & Aguirre-Alvarez, G. (2019). Hydrolyzed Collagen-Sources and Applications. Molecules, 24(22).
15. Edgar, S., Hopley, B., Genovese, L., Sibilla, S., Laight, D., & Shute, J. (2018). Effects of collagen-derived bioactive peptides and natural antioxidant compounds on proliferation and matrix protein synthesis by cultured normal human dermal fibroblasts. Sci Rep, 8(1), 10474.
16. Oesser, S., Schulze, C. H., Zdzieblik, D., & König, D. (2016). Efficacy of specific bioactive collagen peptides in the treatment of joint pain.
    Osteoarthritis and Cartilage, 24, S189.
17. Praet, S. F. E., Purdam, C. R., Welvaert, M., Vlahovich, N., Lovell, G., Burke, L. M., . . . Waddington, G. (2019). Oral Supplementation of Specific Collagen Peptides Combined with Calf-Strengthening Exercises Enhances Function and Reduces Pain in Achilles Tendinopathy Patients. Nutrients, 11(1).
18. Schunck, M., & Oesser, S. (2013). Specific collagen peptides benefit the biosynthesis of matrix molecules of tendons and ligaments. Journal of the International Society of Sports Nutrition, 10(Suppl 1), P23.
19. Alcock, R. D., Shaw, G. C., Tee, N., & Burke, L. M. (2019). Plasma Amino Acid Concentrations After the Ingestion of Dairy and Collagen Proteins, in Healthy Active Males. Front Nutr, 6, 163.
20. Shaw, G., Lee-Barthel, A., Ross, M. L., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity
    augments collagen synthesis. Am J Clin Nutr, 105(1), 136-143.
21. Lis, D. M., & Baar, K. (2019). Effects of Different Vitamin C-Enriched Collagen Derivatives on Collagen Synthesis. Int J Sport Nutr Exerc Metab, 29(5), 526-531.
22. Babraj, J. A., Smith, K., Cuthbertson, D. J., Rickhuss, P., Dorling, J. S., & Rennie, M. J. (2005b). Human bone collagen synthesis is a rapid, nutritionally modulated process. J Bone Miner Res, 20(6), 930-937.
23. Babraj, J. A., Cuthbertson, D. J., Smith, K., Langberg, H., Miller, B., Krogsgaard, M. R., . . . Rennie, M. J. (2005a). Collagen synthesis in human musculoskeletal tissues and skin. Am J Physiol Endocrinol Metab, 289(5), E864-869.
24. Kjaer, M., Jorgensen, N. R., Heinemeier, K., & Magnusson, S. P. (2015). Exercise and Regulation of Bone and Collagen Tissue Biology. Prog Mol Biol Transl Sci, 135, 259-291.
25. Tempfer, H., & Traweger, A. (2015). Tendon Vasculature in Health and Disease. Front Physiol, 6, 330.
26. Close, G. L., Sale, C., Baar, K., & Bermon, S. (2019). Nutrition for the Prevention and Treatment of Injuries in Track and Field Athletes. International Journal of Sport Nutrition and Exercise Metabolism, 29(2), 189-197.
27. Shaw, G., Serpell, B., & Baar, K. (2019). Rehabilitation and nutrition protocols for optimising return to play from traditional ACL reconstruction in elite rugby union players: A case study. J Sports Sci, 37(15), 1794-1803.
28. Clark, K. L., Sebastianelli, W., Flechsenhar, K. R., Aukermann, D. F., Meza, F., Millard, R. L., . . . Albert, A. (2008). 24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. Curr Med Res Opin, 24(5), 1485-1496.
29. Clifford, T., Ventress, M., Allerton, D. M., Stansfield, S., Tang, J. C. Y., Fraser, W. D., . . . Stevenson, E. (2019). The effects of collagen peptides on muscle damage, inflammation and bone turnover following exercise: a randomized, controlled trial. Amino Acids, 51(4), 691-704.
30. Alcock, R. D., Shaw, G. C., & Burke, L. M. (2018). Bone Broth Unlikely to Provide Reliable Concentrations of Collagen Precursors Compared With Supplemental Sources of Collagen Used in Collagen Research. Int J Sport Nutr Exerc Metab, 0(0), 1-8.
31. Eastoe, J. E. (1955). The amino acid composition of mammalian collagen and gelatin. Biochem J, 61(4), 589-600.
32. Iwai, K., Hasegawa, T., Taguchi, Y., Morimatsu, F., Sato, K., Nakamura, Y., . . . Ohtsuki, K. (2005). Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates. J Agric Food Chem, 53(16), 6531-6536.

• L-carnitine is derived from the amino acids lysine and methionine within the human body but can also be ingested from animal products. A deficiency of carnitine is rare, even in vegans. Carnitine is stored within the heart and skeletal muscles, and has several roles.
• An obligatory component of the transfer process for fatty acids from the bloodstream into muscle mitochondria for use as fuel.
  • Buffers excess acetyl-CoA within the mitochondria in order to maintain the rate of fuel delivery from carbohydrate during prolonged endurance exercise and reduce lactate accumulation during high intensity exercise.
  • May play an anti-oxidant role to help muscle recovery and reduce muscle protein breakdown following intense exercise such as heavy training loads or repeated competition performance over short time periods.
• For carnitine supplementation to change fatty acid transport and buffering capability within the muscle mitochondria, it would be necessary to increase muscle carnitine concentration. However, very few studies have measured muscle carnitine concentrations as this is technically challenging to do.
  • There is no evidence for changes in muscle carnitine concentrations following short periods (4 weeks or less) of supplementation, nor in most longer term studies which do not co-ingest carbohydrate with the carnitine.
  • Two longer term studies undertaken in recreational athletes (1.4-3g L-carnitine daily for 12-24 weeks) showed increases in muscle carnitine concentration were possible provided a sufficient amount of carbohydrate (80g) was consumed with each dose of L-carnitine.^1,2 However, the metabolic and performance benefits remain uncertain, with one study showing an increased work output over 30 min all out performance test at 24 weeks supplementation (but no increase at 12 weeks¹) while Shannon et al.² found no impact on high intensity interval training adaptations.
  • A similar carnitine supplementation protocol (2g L-carnitine daily for 12 weeks) but without carbohydrate co-ingestion increased muscle carnitine concentration in vegetarians but not omnivores. No differences were found in energy metabolism or lactate levels during 1 hour of moderate intensity exercise in either group3 across the study.
  • Over the first 12 weeks of supplementation in the study by Wall et al.¹, body fat increased 1.8kg (perhaps as a result of an extra 160g carbohydrate per day) in the control group but did not change in the carnitine group. This may be partly explained by a higher energy expenditure during 30 min exercise at 50% VO_2max in the carnitine-supplemented group.⁴ However, since there were no body fat changes reported by Shannon et al.² using a similar supplementation protocol, it is difficult to know whether this was an impact of the carnitine supplementation or other factors over that extended period of time.
• Preliminary research on muscle pain, muscle disruption (via MRI) and blood markers of muscle damage have found favourable adaptations following 3 weeks L-carnitine supplementation.⁵
• One study of 9 weeks supplementation of 2g L-carnitine L-tartrate daily during resistance training found reductions in markers of oxidative stress and improvements in muscle strength but not muscle mass.⁶
• Carnitine is also a popular weight loss supplement due to its proposed role in facilitating fat oxidation. However, there is a lack of evidence supporting the efficacy of carnitine in further enhancing fat loss.

Carnitine may be useful in several clinical settings where carnitine deficiency may be induced, such as maintaining brain and muscle function in the elderly and in the treatment of some forms of cardiovascular disease. Vegetarians may be particularly responsive to carnitine supplementation, presumably because of lower dietary intake.

• Carnitine is generally found in powdered form, which may be encapsulated to better enable ingestion of specific doses.
  • The most common variant used for athletes is L-carnitine L-tartrate.
  • There are also liquid forms of L-carnitine on the market, however this form of carnitine has generally not been researched and rarely achieves carnitine doses used in research studies.
  • Other forms of carnitine, such as acetyl-l-carnitine and propionyl-l-carnitine have been used in clinical settings only.

• In theory, athletes most likely to benefit from carnitine supplementation include endurance competition events (>30 mins duration), prolonged high intensity exercise (such as team sports), and aiding in recovery during heavy training loads or resistance exercise.
• Recommended dose is 1.4-3g L-carnitine (2-4g L-carnitine L-tartrate) taken as a split dose twice a day for 12 weeks or longer.
  • Each dose should be consumed with a carbohydrate containing meal to facilitate enhanced uptake.
• Shorter term supplementation periods (1.4-3g L-carnitine / day over 3-9 weeks) may be considered where reduction in muscle soreness and damage incurred by heavy exercise is the goal.

Lack of clarity over benefits of short-term supplementation.

Short term supplementation studies which have been undertaken on athletes and active individuals have shown no consistent responses to exercise performance or metabolism. This is due to a wide variance in supplementation duration (single dose pre-exercise through to 4 weeks daily supplementation), training status of participants, the implementation of dietary or exercise controls before testing, and the actual exercise test used/ outcome measured.

Long term supplementation requires each dose to be co-ingested with a significant amount of carbohydrate.

Very few studies have shown an uptake of supplemental carnitine into muscle, but the limited evidence suggests a large dose of carbohydrate (80g with each dose) is required over at least 12 weeks in order to achieve this. There has been no research on whether this dose of carbohydrate could be altered according to body weight or if this could be adjusted according to co-ingestion with other macronutrients, possibly enabling guidance to be adjusted to merely encourage ingestion at main meals. The additional carbohydrate, and the requirement to specifically be timed with the carnitine supplement twice daily, is unlikely to align with the caloric needs and nutrient timing that is optimal for each athlete, during each phase of training, over the period of supplementation.

Very few studies have been undertaken on elite athletes.

As such, the applicability of the research to elite athletes is uncertain.

L-carnitine may increase fasting plasma trimethylamine-N-oxide (TMAO) levels.

Increased TMAO has been linked to atherogenesis and a higher risk of cardiovascular events.⁵

L-carnitine consumption may cause mild gastrointestinal symptoms.

• Some reports of nausea, vomiting, stomach cramps and diarrhoea have been reported during supplementation. Akin to guidance for other supplements that can result in intestinal symptoms, co-ingestion with meals may be advisable.
• Consuming more than 3g/day may result in a ‘fishy’ body odour.

Supplement safety information and batch tested product list
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Wall, B.T., Stephens, F.B., Constantin-Teodosiu, D., Marimuthu, K., Macdonald, I.A., Greenhaff, P.L. (2011). Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. J Physiol, 589, 963-973.
2. Shannon, C.E., Ghasemi, R., Greenhaff, P.L., Stephens, F.B. (2018). Increasing skeletal muscle carnitine availability does not alter the adaptations to high intensity interval training. Scan J Med Sci Sports, 28, 107-115.
3. Novakova, K., Kummer, O., Bouitbir, J., Stoffel, S.D., Hoerler-Koerner, U., Bodmer, M., et al. (2016). Effects of L-carnitine supplementation on the body carnitine pool, skeletal muscle energy metabolism and physical performance in male vegetarians. Eur J Nutr 55, 207-217.
4. Stephens, F.B., Wall, B.T., Marimuthu, K., Shannon, C.E., Constantin-Teodosiu, D., Macdonald, I.A., Greenhaff, P.L. (2013). Skeletal muscle carnitine loading increases energy expenditure, modulates fuel metabolism gene networks and prevents body fat accumulation in humans. J Physiol, 591, 4655-4666.
5. Sawicka, A.K., Renzi, G., Olek, R.A. (2020). The bright and dark sides of L-carnitine supplementation: a systematic review. JISSN, 17, 49.
6. Koozehchian, M.S., Daneshfar, A., Fallah, E., Agah-Alinejad, H., Samadi, M., Kaviani, M. et al. (2018). Effects of nine weeks L-carnitine
   supplementation on exercise performance, anaerobic power and exercise-induced oxidative stress in resistance-trained males. J Exerc Nutr Biochem, 22, 7-19.

• Ketone bodies (acetone, acetoacetate and beta-hydroxy-butyrate [ßHB]) are chemicals produced by the liver during periods of low energy or low carbohydrate availability, with high circulating levels seen during starvation, prolonged fasting and extreme carbohydrate restriction (e.g. ketogenic low carbohydrate high fat [LCHF] diets).
• ßHB is the most important ketone body (“ketone”) from a metabolic perspective and blood concentrations of 1-3 mmol/L are considered to be the optimal range for it to exert metabolic effects.¹
• Ketone supplements are taken to acutely increase blood concentrations of ßHB/ ketones without the need to undertake energy or carbohydrate restrictions. A range of benefits has been proposed or investigated including:
  • Direct benefit to physiological and cognitive aspects of endurance performance via fuelling mechanisms^2-4
  • Superior post-exercise recovery with potential use as a chronically used supplement⁵
  • Strategic chronic or periodised use to enhance health and training adaptations⁶
• The first major interest in the use of oral ketone supplements in sports is attributed to work of Oxford University’s Professor Kieran Clarke, who developed a ketone ester (“DeltaG”) that was part of a campaign to prepare British athletes for the 2012 London Olympic Games. This product has also been highly used within professional road cycling teams for the benefits previously identified, as well as other claims such as appetite suppression to support body composition goals.

• Ketone supplements are available in three different forms.
  • Ketone salts (sodium, magnesium or calcium salts of the ßHB).
  • 1-3- Butanediol (precursor to ßHB).
  • Ketone esters.
    • The ketone mono-ester [®-3-hydroxybutyl (R)-3-hydroxy-butyrate) developed as DeltaG at Oxford University is now commercialised as HVMN Ketone Ester.
    • Patents for di-esters have been established but are only involved in clinical research.
• Some manufactured ketone supplements contain a racemic mixture (i.e. equal parts D- and L- stereoisomers) of ßHB. Only the D-isomer
  (R-ßHB) is considered to have high metabolic activity.

Acute use for exercise

• A variety of protocols have been investigated in scientific trials with the most common involving the intake of the ketone ester before, and sometimes during, endurance exercise.
• Total dose = ~570-750 mg/kg (40-60 g). Note that one 40 g bottle of the Ketone Ester contains 25 g of the active compound.
• The protocols of use associated with testimonials in some sports (e.g. road cycling) are unknown.

Chronic or periodic use

• Protocols recommended for chronic or periodic use have not yet been established.

Current evidence to support the use of ketone supplements is summarised in the table below. >

Equivocal scientific support

• The evidence for benefits of acute or chronic supplementation on health and performance is unclear. There is a wide range in the protocols of use, and in the scenarios of exercise, in which it has been investigated. It is difficult to integrate the various findings of these studies.
• The effects of high blood ketone levels on metabolism and other physiological outcomes is extremely complex. Different protocols of use may achieve variable effects on the timing and increase in blood ßHB concentrations with differential effects on substrate metabolism and physiological effects. It may be difficult to pinpoint beneficial uses and the window of benefit may be small. In addition, some of the effects may impair sports performance.
  • Ketone supplementation creates major effects on substrate use (reduces glycolysis, lipolysis, glycogen use and increases use of intramuscular triglycerides. Some of these effects may be counter-productive to some sports scenarios.
  • Causes increase in blood acidity which may be counter-productive to some sports scenarios.
• Some recent studies suggest that the ßHB provides a minor substrate for the muscle (~5% of fuel use) and the claimed benefits to exercise economy (reduced oxygen use) are equivocal.
• The current investigations on ketone ester supplementation fail to cover most of the anecdotal uses/testimonials and the claims around longterm/chronic use.

Nuances of specific supplements

• Ketone ester supplements
  • These are expensive and often hard to obtain due to limited capacity for commercial manufacture (~$50 per 25 g bottle for HVMN supplement).
• Ketone salts
  • These produce a high salt load and gastrointestinal side effects.
  • These appear extremely unlikely to sufficiently increase blood ßHB (> 1 mmol/L).

Perceptions around their use

• Ketone ester supplements are not included on the WADA Prohibited List and it would seem impractical as well as illogical for them to meet the criteria for such a ban.
• Nevertheless, the initial use of “DeltaG” supplement by UK sporting teams and professional cycling teams has received much media/public criticism as being “frankenscience”.

Supplement safety information
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Evans, M., Cogan, K.E., & Egan, B. (2017). Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation. J Physiol, 595(9), 2857-71.
2. Shaw, D.M., Merien, F., Braakhuis, A., Maunder, E., & Dulson, D.K. (2020). Exogenous Ketone Supplementation and Keto-Adaptation for Endurance Performance: Disentangling the Effects of Two Distinct Metabolic States. Sports Med, 50, 641-656.
3. Valenzuela, P.L., Castillo-García, A., Morales, J.S., & Lucia, A (2020). Update on the Acute Effects of Ketone Supplements in Athletes. Adv Nutr, 11(4),1050-1.
4. Margolis, L.M. & O’Fallon, K.S. (2019). Utility of Ketone Supplementation to Enhance Physical Performance: A Systematic Review. Adv Nutr. 11, 412-419.
5. Poffe, C., Ramaekers, M., Van Thienen, R., & Hespel, P. (2019) Ketone ester supplementation blunts overreaching symptoms during endurance training overload. J Physiol, 597(12), 3009-27.
6. Poffé C, Hespel P. Ketone bodies: beyond their role as a potential energy substrate in exercise. J Physiol. 2020 Nov;598(21):4749-50.
7. Valenzuela, P.L., Castillo-Garcia, A., Morales, J.S., & Lucia, A. (2020) Perspective: Ketone Supplementation in Sports-Does It Work? Adv Nutr. In press.
8. Valenzuela, P.L., Morales, J.S., Castillo-García, A., & Lucia, A. (2020) Acute Ketone Supplementation and Exercise Performance: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Int J Sports Physiol Perform,15(3), 298-308.
9. Cox, P.J., Kirk,T,. Ashmore, T., Willerton, K., Evans, R., Smith A, et al. (2016). Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes. Cell Metab, 24(2), 256-68.
10. Poffe, C., Ramaekers, M., Bogaerts, S., & Hespel, P. (2021). Bicarbonate Unlocks the Ergogenic Action of Ketone Monoester Intake in Endurance Exercise. Med Sci Sports Exerc.53, 431-441.
11. Poffe, C., Wyns, F., Ramaekers,. M, & Hespel, P. Exogenous Ketosis Impairs 30-min Time-Trial Performance Independent of Bicarbonate Supplementation. Med Sci Sports Exerc, in press.

• Fish (or marine) oil comprises of >50 fatty acid isomers. These include the major groupings of saturated, monounsaturated and polyunsaturated fatty acids (divided into omega-6 and omega-3). The relative composition varies according the type of fish from which the oil is derived.
• By far the most abundant of the fatty acids in fish oil, and the basis for its consumption, are the omega-3 polyunsaturated fatty acids; Eicosapentaenoic Acid [EPA; 20:5n-3] and Docosahexaenoic Acid [DHA; 22:6n-3].
• When EPA and DHA are provided in the diet, through either food such as fish or as a supplemental fish oil, the fatty acid profiles of the plasma, whole blood and red blood cells membranes are modified. These increased concentrations of EPA and DHA reduce the overall omega-6 / omega-3 ratio and specially the arachidonic acid (AA) / eicosapentaenoic acid (EPA) ratio in favour of anti-inflammation.
• Most notably, these changes in the proportion of EPA and DHA of the red blood cell membrane, represent the long-term dietary intake of these polyunsaturated fatty acids and act as a biomarker for other tissues. For example, skeletal muscle, heart and brain avidly incorporate membrane DHA. Remodelling of these membranes has been shown to…
  • Improve the omega-3 status: The Omega-3 Index (O3I) is the relative sum of EPA% + DHA% in the red blood cell membrane. It is desirable for the O3I to be >8%. As a consequence of increasing the O3I, the omega-6/omega-3 ratio will be reduced <5 and the AA / EPA <11, which are promoted ratios for cardio-protection (O3I) and anti-inflammation (omega-6 / omega-3 and AA/EPA).^1,2
  • Modify physiological function: Preliminary evidence supports that an improved omega-3 status i). May reduce physiological strain, through for example, a reduction in heart rate1,3 ii). Aid in the recovery process via an anti-inflammatory (EPA) and pro-resolvin effects (DHA) (which turn off the inflammation process)4 and iii). Potentially protect against a reduction in muscle protein synthesis during periods of immobilisation, such as injury.⁵

• The most common form of fish oil is the capsule (or ‘softgel’) with a composition of gelatin, glycerine and purified water. In general, the standard total mass range for each capsule is 1000 – 1500 mg At this total mass, each capsule provides a varied dose of the two key long chain omega-3 polyunsaturated fatty acids; EPA and/ or DHA.
• Fish oil can also be purchased in a non-capsulated form or bottled. The dose of EPA and DHA will also vary between brands, according to the fish stock. The quantity of long chain omega-3 fatty acids is usually described according to the volume of a teaspoon (5 mL).
  • The following table provides a comparison of the predominant types of commercially available fish oils. It is essential to check the content of the fish oil for the concentrations of the active components, EPA and DHA. In addition, the EPA and DHA are supplied in a variety of usual forms. Free fatty acids, natural triglycerides and re-esterified triglycerides tend to have the highest bioavailability.

  Table 1: Comparison of fish oils providing EPA and DHA

>

Type of fish oil	Usual dose per 1 gram oil (EPA / DHA)	Usual forms
EPA rich oil	200-500 mg / 100 mg	Free fatty acids, natural triglycerides, ethyl esters (synthesised and least bioavailable), re-esterified  triglycerides and phospholipids.
DHA rich oils	<100 mg / 500-750 mg

• The standard western diet, largely devoid of consistent seafood consumption, means that the average intake of EPA and DHA, for an individual, is likely below the recommendations for avoiding a deficiency in omega-3 fatty acids. It is recommended that at least two servings per week of fatty fish are included in the diet, in addition to food sources that provide alpha-linolenic acid (ALA; 18:3n-3).
• The food first approach, as part of the overall diet, should always be considered. The following example servings of fish, provide varied amounts of the long chain fatty acids, EPA and DHA. For canned fish, always check the product description, as fish sources can vary in their content of EPA and DHA.

Table 2: Foods that provide good sources of EPA and DHA

>

Total EPA + DHA	Example servings of fish and seafood (* serving size ~ 180 g; † serving size ~ 100 g )
500 mg	Australian salmon*, fresh or canned sardines*, canned salmon* or tuna*, lipped mussels†, mackerel*, rainbow trout*
300-500 mg	Herring*, trevally*, fresh tuna*, calamari†, oysters†
<300 mg	Australian bass*, flathead*, dory*, scallops†, prawns†, octopus†

• Services are available commercially to determine the O3I. Athletes with a low dietary intake of EPA + DHA may benefit from tracking their improvements associated with the commencement of a supplement. A dry blood spot is collected (fasting state), from a self-conducted finger prick (in the home). The sample is sent via the mail to an internationally accredited pathology centre or university laboratory for analysis. A report is produced that includes a whole blood fatty acid profile, the O3I and the inflammatory ratios omega-6/omega-3 (target <5) and AA/EPA (target <11).

Figure 1: Omega-3 Index (red blood cell EPA + DHA%) with Australian median (estimated) value. The target is to elevate and then maintain an O3I >8% (green zone).

• The first objective, and overriding principle for correcting an omega-3 intake deficiency, is a consistent and long term provision of EPA and DHA in the diet. It is possible to achieve an optimal concentration of EPA and DHA in the circulation and the tissues using whole foods (as listed above). A combined EPA + DHA intake of 500-600 mg per day is the minimum target and careful planning of the diet is necessary to achieve this consistency. Alternately, for those with no intake or inconsistent dietary sources of omega-3, a daily supplement of 1-2 capsules per day (depending on the oil and brand) will achieve equivalent outcomes for modifying membranes.
• The second objective is to maximise the omega-3 status to aid physiological function of heart and muscle, particularly in times of high physiological strain and need for recovery. The preliminary, aggregated evidence, suggests that a combined EPA + DHA dose of ≥1000 mg per day is linked to reduced physiological strain (such as a reduction in heart rate), improvement of exercise induced inflammation response and possible preservation of muscle structure and function during specific conditions such as immobilisation.
• The following table summarises the key points to optimising, maximising and maintaining circulating and tissue concentrations of EPA and DHA.

Table 1: Summary of current evidence for fish oil consumption >

Storage

• The long chain omega-3 fatty acids contained in fish oil are oxidisable. Most oils will contain the antioxidant, alpha tocopherol, to protect the EPA and DHA from degrading. It is best practice to make sure that capsules are in date, stored in the purchased container and kept in a consistently cool environment (a fridge is also fine) away from direct light.

Bleeding

• The European Food Safety Authority considers intakes up to 5 grams of fish oil per day safe.⁶ The EPA active component of fish oil can modify the coagulation properties of the blood involved bleeding. However, a recent randomised placebo-control trial reported no increased risk of peri-operative bleeding⁷ and a systematic literature review (of 52 studies) concluded that fish oil supplementation did not increase the risk of bleeding during or after surgery.⁸ In the advent that surgery is required, some pre-operative assessments will request information about current fish oil consumption.

Gastrointestinal discomfort, allergies and the vegan diet

• Research involving therapeutic doses (>5 g of total oil) have sometimes reported gastrointestinal discomfort, in a minority of participants. Consuming the fish oil (capsule) with other foods results in the digestion and absorption occurring alongside other macro and micronutrients. The capsules are also designed to dissolve slowly and in time for movement of the oil into the duodenum (small intestine). Consuming a non-capsulated fish oil product (usually a teaspoon of oil) without other foods, is more likely to result in reflux and after taste, although some of these non-capsulated oils are flavoured to improve palatability.
• A small proportion of the population are allergic to fish and seafood products. Before consuming, it is worth considering if this applies to each individual.
• Athletes consuming a plant based diet will most likely have a low omega-3 status (reflected by the O3I <4.5%). Although fish oil is avoided in the vegan diet, EPA and DHA can be sourced from algal oil and has been demonstrated to be effective in the wider population in raising the O3I.

Fish oil in combination capsules

• Several major brands combine fish oil with either anti-oxidants, such as curcumin, or vitamin D. To date, there are few studies published exploring the efficacy of combined capsules although some seem promising. For example, a combined fish oil and vitamin D supplement was reported to reduce the number of URTI symptom days in recreational athletes.⁹
• Krill oil also contains a good source of EPA and DHA. Krill oil differs from fish oil in that the major form of the long chain omega-3 fatty acids are phospholipids. This factor may improve membrane incorporation although studies in trained groups are limited.¹⁰ Krill oil also naturally contains the antioxidant astaxanthin which provides an opportunity combining their intake.

Global Organisation for EPA and DHA Omega-3
www.goedomega3.com

National Heart Foundation
www.heartfoundation.org.au/getmedia/741b352b-1746-48f4-806a-30f55fddfad2/Health_Professional_QA_Fish_Omega3_Cardiovascular_Health.pdf

Supplement safety information
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Peoples, G. E., and McLennan, P. L. (2016) Chapter 10: Fish Oil for Physical Performance in Athletes in Fish and Fish Oils in Health and Disease. Editors Raatz S, Bibus D. USA, Elsevier Inc. ISBN 978-0-12-802844-5.
2. Calder, P. (2013) Omega-3 polyunsaturated fatty acids and inflammatory processes: nutrition or pharmacology? Br J Clin Pharmacol. 75 (3); 645
3. Macartney, M.J., et al. (2014) Intrinsic heart rate recovery after dynamic exercise is improved with increased omega-3 index in healthy males. BJN. 112, 1984–1992.
4. Philpott, J. D. et al. (2018) Applications of omega-3 polyunsaturated fatty acid supplementation for sport performance. Res Sport Med, 27(2):219-237.
5. McGlory, C., et al. (2019) The Influence of Omega-3 Fatty Acids on Skeletal Muscle Protein Turnover in Health, Disuse, and Disease. Frontiers in Nutr, 6; 144.
6. European Food Safety Authority (2012) Scientific opinion on the tolerable upper intake level of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA). EFSA J. 10:2815
7. Akintoye, E, et al. (2018) Fish oil and perioperative bleeding. Circ Cardiovasc Qual Outcomes. 11:004584.
8. Begtrup, KM, et al (2017). No impact of fish oil supplements on bleeding risk: a systematic review. Dan Med J. 64:1–11.
9. Da Boit, M. et al. (2015) The effect of fish oil, vitamin D and protein on URTI incidence in young active people. Int J Sports Med. 36(5): 426-430.
10. Daboit, M. et al (2015) The effect of krill oil supplementation on exercise performance and markers of immune function. Plos One. 1-14

Curcumin is the most abundant phenolic compounds in turmeric, a spice commonly found in curry powders and sauces with a long history of use in cooking and in traditional Indian and Chinese systems of natural medicine.¹ More recently, curcumin has been investigated for medicinal properties, health, and possible sport recovery and performance benefits. Turmeric is “generally recognised as safe” by the US FDA, indicating that it can be a safe food additive. However, curcumin in an unstable compound and its bioavailability is very poor. As such, recent efforts have focused on developing curcumin formulations with greater bioavailability and systemic tissue distribution. Broadly, these formulations include lipid additions (turmeric oil and piperine), adsorption on matrices (lecithin), and curcumin size reduction to nano particles.²

Curcumin has a number of potential health/ performance benefits

• In health, curcumin has been shown to aid in the management of oxidative stress and inflammatory conditions such as metabolic syndrome and arthritis.³
• Curcumin has been found to have non-steroidal anti-inflammatory drug-like actions as evidenced by a largely dampened activity of markers of oxidant and inflammatory pathways (e.g. COX-2 and NF-kB signalling) in disease^{4, 5}, although clear associations between pathway markers and muscle performance in athletes remain unclear.
• Curcumin has been associated with reduced exercise-induced muscle damage (EIMD) and exercise-induced muscle soreness (EIMS), plus lowered delayed-onset muscle soreness (DOMS). As such, curcumin may be used in the treatment of pain and inflammation following exercise, reduction of oxidative stress following exercise, plus alleviation of muscle damage, improving muscle recovery, EIMS and DOMS.
• Curcumin supplementation usually has no noticeable side effects. However, there are safety concerns when consumed in doses > 2g/day.
• Effects of long-term supplementation on the magnitude-efficacy of the training response and adaptability are at the time of writing unknown, but warrant investigation.

Mechanistic evidence and nature of benefits for athletes.

• Reduced pain following heavy muscular exercise loading is reported by way of lower DOMS or other muscle soreness scores in most^6-10 but not all studies.¹¹
• The reduction in DOMS is also associated with improved joint range of motion, suggesting reduced musculotendinous stiffness⁶. Curcumin also lowers the marker of muscle damage - creatine kinase (CK) - concentration within the blood, suggesting the reduced muscle soreness findings may be associated with attenuation of muscle cell damage. More conclusively, a recent meta-analysis found a significant effect of curcumin supplementation on reducing CK (weighted mean difference [WMD] = -48.5 IU.L-1 ; 95% CI: -80.7, -16.4;p=0.003) and muscle soreness index (WMD = -0.5; 95% CI: -0.8, -0.2; p=0.001), leading to the author conclusion that “curcumin may be known as a priority EIMD recovery agent in interventions”.¹⁰
• Reduced inflammation is inferred from a reduction in markers of systemic inflammatory modulatory pathways, models which were developed largely from in vitro research models within the (health) therapeutic use setting. Additionally, advanced glycation end-products (AGEs) produced from muscle-damaging eccentric exercise (e.g. jumping, resistance training, and hard running), are associated with reduced subsequent performance, although may not be mechanistically determinant but a side effect. Nevertheless, 3 months of curcumin plus Boswellia serrata (BSE) gum resin supplementation was shown to lower AGEs and lipid- peroxidation outcomes in athletes.¹² Six days of curcumin supplementation during a bout of EMID attenuated post-exercise concentration of the inflammatory cytokines IL8 and TNF-α, but not IL6 or IL10.11 Meanwhile in a similar experimental model, curcumin increased IL6 concentrations at 0-h (31 %; 90%CI ±29 %) and 48-h (32 %; ±29 %) relative to baseline, but decreased IL-6 at 24-h relative to post-exercise (-20 %; ±18 %) 7. In contrast, Tanabe et al.¹³ reported no significant changes in IL6 and TNF-α.
• Reduced oxidative stress markers post-exercise in the urine or blood support other in vitro models suggesting anti-oxidant effects. For example, curcumin can modulate the activation of T-cells, B-cells, NK cells, neutrophils, macrophages, and dendritic cells¹⁴, and at low doses, curcumin can also enhance antibody responses, suggesting it may modulate the immune system.¹⁵ However, in athletes, results are mixed and not all chronic (e.g. 28 d) supplementation studies show consistent effects on system oxidative stress or inflammatory markers.^{7, 9}

Effects on recovery and performance in athletes.

• A selection of well-designed and executed studies suggest worthwhile improvements in skeletal muscle function following a single bout of strenuous or damaging exercise; whether these largely laboratory-based surrogate muscle-function outcomes translate to real-world performance remains to be established.
  • Nicol et al.⁷ supplemented athletes with a very high dose of curcumin stated as equivalent to 0.3 g/kg/d or apparently ~1060 mg twice daily (from 2.5 g curcumin), or control, for 2.5 days before and 2.5 days after severe EMID. Associated with moderate-large standardised reductions in pain perception during single-leg squat was a small increase in single-leg jump performance (15%; 90 %CL ± 12%) with curcumin supplementation.
  • Tanabe et al.⁷ gave 14 healthy men 150 mg/d curcumin before and 12 h after maximal eccentric arm exercise. Maximal voluntary contraction torque decreased less and recovered faster (e.g. 4 days post-exercise: -31 ± 13 % vs. -15 ± 15 %) with curcumin compared with placebo.
  • Delecroix et al.¹⁶ gave 10 elite rugby players 6 g curcumin + 60 mg piperine/d for 48 h before and following EIMD. Curcumin supplementation resulted in a moderate reduction in sprint mean power output (-1.1; 90%CI -1.9 to -0.9) at 24-h post exercise, but no other outcomes were clear. The lack of a consistent performance outcome and the addition of piperine (which may enhance bioavailability of curcumin up to 2000%), needs to be considered in the context of this study.
  • Hillman et al.6 studied the effects of a 500 mg dose of curcumin supplementation twice daily for 10 days (6 days pre, day of and 3 days post exercise) on DOMS and muscle power following plyometric exercise in 22 men and women. Following 5 x 20 drop jumps on day 7, vertical jump test performance was reduced in placebo but maintained following curcumin supplementation (curcumin benefit +1.6 inches 90%CI 0.63 to 2.6).
  • Several other studies were conducted, but used measures of performance that have poor reliability. For example, Jäger et al.¹⁷ supplemented two doses for 8 weeks but report mostly inconclusive results to muscle function, probably related to the use of isokinetic peak torque as the performance measure¹⁷, which has poor reliability.¹⁸
  • Overall, there is building evidence to suggest a benefit to recovery of muscle performance in power or explosive activities from several days of curcumin supplementation at specified doses (500-2500 mg of curcumin twice daily). However, the evidence remains mixed, coupled with confounding effects from co-ingredients, and more high-quality studies in explosive, power and sprint, plus endurance models, are required before firm dose efficiacy and performance-based conclusions can be formed.

• Curcumin is a yellow powder most often available in capsule form.
  • Examples of commercial curcumin in unmodified form are CurcuFresh⁹ and combined formulation.⁷
  • Commercial products with adjunct ingredients to improve bioavailability include Meriva®, a Phytosome® delivery system⁸, CurcuWIN®, which contains other antioxidants.^{17, 19}
• Format and Bioavailability
  • Unformulated curcumin has poor bioavailability due to poor absorption, rapid metabolism and elimination from the body.²⁰ In humans, when unformulated curcumin was administered, only low levels of curcumin were detected in the serum of one-third of the individuals given very high doses of curcumin (10,000-12,000 mg/day).²¹
  • Nutraceutical companies have trialled formulating curcumin with adjuvants (e.g. piperine, turmeric oil, etc), nanoparticles, liposomes, micelles, nano-curcumin, and phospholipid complexes²⁰, some of which may also be bioactive making a clean inference to the bioaction of curcumin difficult. Processing may also provide curcumin metabolites which have a shorter half-life^{20, 22}. Some authors have used more bioavailable forms.^{8, 11, 19}
  • Only two studies have used commercially available supplements^{7, 9}, which potentially require higher doses, but are cheaper for consumers. Currently, there is a lack of clarity on what products are most efficacious and more research and consumer data is required.
  • Effective dose of curcuminoids (the bioactive fraction of total curcumin) is probably key to optimal bioactivity i,e. aiming for a total daily dose of at least 200 to 1000 mg per day. There is uncertainty on the safety of curcumin larger than 2g/day and no more than 8 g of total curcumin should be taken per day.²³
  • Currently, the optimal dose of curcumin for post-exercise recovery is unknown. Previous studies have used 90 to 6000 mg/d doses, with 90 mg the lowest effective dose to show some impact on recovery markers24. Clear benefits to subsequent performance were seen with 500 mg⁶ or 2.5 g⁷ of curcumin taken twice daily, for 10 or 5 days respectively.
  • Effective dosage for an individual may also be influenced by training volume and intensity, as exercise load affects (generally increases) endogenous antioxidant response. The amount of exogenous antioxidant-rich foods within the normal diet (e.g. fruits and vegetables) can also increase the antioxidant response.

• Curcumin as a supplement will most frequently come in capsule form.
  • The scope of research to date covers a 2 day to 12-week supplementation period prior to a test bout of exercise and 24-72 h recovery regimen. The clearest evidence for efficacy is 2-5 day supplementation at a high dose (2 x 500-2500 mg of curcumin per day; or a dose of a hybrid product providing around 200-1000 mg of curcuminoids per dose) prior to exercise that the athlete is interested in recovering from.
• Summary of some protocols of use from various Turmeric extracts summarised in²⁵:
  • 180 mg-5 g/day of curcumin.
  • 180 mg/day of curcumin Theracurmin® (nano-curcumin).
  • 500 mg/day of Meriva® curcumin (with food-grade lecithin).
  • 6 g of Turmeric extract + 60 mg of piperine/day.
  • 400 mg/day of Longvida® curcumin (offers a 7.5-hour half-life, compared to the 2-3 hour half-life of standard curcumin).

Effective dose and co-ingredient risk

• Optimal, threshold, and minimal effective dose and bioavailability of the native and advanced available compounds remain to established.
• Advanced formulations often carry additive and adjunct compounds that may be bioactive. Sports dietitians and athletes should be cautious in regards to inadvertent doping.
• Turmeric extracts contain active non-curcuminoid fractions of polysaccharides (turmrerosacchardies) and Turmeric oils. There is weak evidence for the efficacy of these products (Turmacin®) in improving pain threshold and range of motion in healthy participants.²⁶

Unknown effects of long-term use on training response

As with some other compounds that dampen the oxidative and pro-inflammatory response to exercise (e.g Vitamin E), the possibility of reducing the training-response signal for adaptation requires systematic investigation. Until this work is complete, coaches and athletes should be aware that the long-term effects of curcumin on training adaptation is unknown.

Supplement safety information and batch tested product list
www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport

1. Wongcharoen, W., & Phrommintikul, A. (2009). The protective role of curcumin in cardiovascular diseases. Int J Cardiol, 133(2), 145-151.
2. Stohs, S. J., Chen, O., Ray, S. D., Ji, J., Bucci, L. R., & Preuss, H. G. (2020). Highly Bioavailable Forms of Curcumin and Promising Avenues for Curcumin-Based Research and Application: A Review. Molecules, 25(6).
3. Hewlings, S. J., & Kalman, D. S. (2017). Curcumin: A Review of Its Effects on Human Health. Foods (Basel, Switzerland), 6(10), 92.
4. Aggarwal, B. B., Sundaram, C., Malani, N., & Ichikawa, H. (2007). The molecular targets and therapeutic uses of curcumin in health and disease (Vol. null).
5. Vane, J. R., & Botting, R. M. (1998). Anti-inflammatory drugs and their mechanism of action. Inflammation Research, 47(2), 78-87.
6. Hillman, A. R., Gerchman, A., & O’Hora, E. (2021). Ten Days of Curcumin Supplementation Attenuates Subjective Soreness and Maintains Muscular Power Following Plyometric Exercise. J Diet Suppl, 1-15.
7. Nicol, L. M., Rowlands, D. S., Fazakerly, R., & Kellett, J. (2015). Curcumin supplementation likely attenuates delayed onset muscle soreness (DOMS). Eur J Appl Physiol, 115, 1769-1777.
8. Drobnic, F., Riera, J., Appendino, G., Togni, S., Franceschi, F., Valle, X., . . . Tur, J. (2014). Reduction of delayed onset muscle soreness by a novel curcumin delivery system (Meriva®): a randomised, placebo-controlled trial. J Int Soc Sports Nutr, 11, 31.
9. Basham, B., Waldman, H., Krings, B., Lamberth, J., Smith, J., & McAllister, M. (2020). Effect of Curcumin Supplementation on Exercise-Induced Oxidative Stress, Inflammation, Muscle Damage, and Muscle Soreness. Journal of Dietary Supplements, 17(4), 401-414.
10. Fang, W., & Nasir, Y. (2020). The effect of curcumin supplementation on recovery following exercise-induced muscle damage and delayed-onset muscle soreness: A systematic review and meta-analysis of randomized controlled trials. Phytother Res.
11. McFarlin, B. K., Venable, A. S., Henning, A. L., Sampson, J. N. B., Pennel, K., Vingren, J. L., & Hill, D. W. (2016). Reduced inflammatory and muscle damage biomarkers following oral supplementation with bioavailable curcumin. BBA clinical, 5, 72-78.
12. Chilelli, N. C., Ragazzi, E., Valentini, R., Cosma, C., Ferraresso, S., Lapolla, A., & Sartore, G. (2016). Curcumin and Boswellia serrata Modulate the Glyco-Oxidative Status and Lipo-Oxidation in Master Athletes. Nutrients, 8(11).
13. Tanabe, Y., Maeda, S., Akazawa, N., Zempo-Miyaki, A., Choi, Y., Ra, S. G., . . . Nosaka, K. (2015). Attenuation of indirect markers of eccentric exercise-induced muscle damage by curcumin. Eur J Appl Physiol, 115(9), 1949-1957.
14. Jagetia, G. C., & Aggarwal, B. B. (2007). “Spicing up” of the immune system by curcumin. J Clin Immunol, 27(1), 19-35.
15. Gautam, S. C., Gao, X., & Dulchavsky, S. (2007). Immunomodulation by curcumin. Adv Exp Med Biol, 595, 321-341.
16. Delecroix, B., Abaïdia, A. E., Leduc, C., Dawson, B., & Dupont, G. (2017). Curcumin and Piperine Supplementation and Recovery Following Exercise Induced Muscle Damage: A Randomized Controlled Trial. J Sports Sci Med, 16(1), 147-153.
17. Jäger, R., Purpura, M., & Kerksick, C. M. (2019). Eight Weeks of a High Dose of Curcumin Supplementation May Attenuate Performance Decrements Following Muscle-Damaging Exercise. Nutrients, 11(7), 1692.
18. Hopkins, W. G., Schabort, E. J., & Hawley, J. A. (2001). Reliability of power in physical performance tests. Sports Med, 31(3), 211-234.
19. Oliver, J. M., Stoner, L., Rowlands, D. S., Caldwell, A. R., Sanders, E., Kreutzer, A., . . . Jäger, R. (2016). Novel Form of Curcumin Improves Endothelial Function in Young, Healthy Individuals: A Double-Blind Placebo Controlled Study. Journal of Nutrition and Metabolism, 2016, 1089653.
20. Anand, P., Kunnumakkara, A. B., Newman, R. A., & Aggarwal, B. B. (2007). Bioavailability of curcumin: problems and promises. Mol Pharm, 4(6), 807-818.
21. Lao, C. D., Ruffin, M. T. t., Normolle, D., Heath, D. D., Murray, S. I., Bailey, J. M., . . . Brenner, D. E. (2006). Dose escalation of a curcuminoid formulation. BMC Complement Altern Med, 6, 10.
22. Prasad, S., Tyagi, A. K., & Aggarwal, B. B. (2014). Recent developments in delivery, bioavailability, absorption and metabolism of curcumin: the golden pigment from golden spice. Cancer Res Treat, 46(1), 2-18.
23. Hsu, C. H., & Cheng, A. L. (2007). Clinical studies with curcumin. Adv Exp Med Biol, 595, 471-480.
24. Takahashi, M., Suzuki, K., Kim, H. K., Otsuka, Y., Imaizumi, A., Miyashita, M., & Sakamoto, S. (2014). Effects of curcumin supplementation on exercise-induced oxidative stress in humans. Int J Sports Med, 35(6), 469-475.
25. Suhett, L. G., de Miranda Monteiro Santos, R., Silveira, B. K. S., Leal, A. C. G., de Brito, A. D. M., de Novaes, J. F., & Lucia, C. M. D. (2020). Effects of curcumin supplementation on sport and physical exercise: a systematic review. Critical Reviews in Food Science and Nutrition, 1-13.
26. Raj, J. P., Venkatachalam, S., Racha, P., Bhaskaran, S., & Amaravati, R. S. (2020). Effect of Turmacin supplementation on joint discomfort and functional outcome among healthy participants – A randomized placebo-controlled trial. Complementary Therapies in Medicine, 53, 102522.

N-Acetylcysteine (NAC) is an amino acid and powerful antioxidant. It is a thiol containing compound that acts to minimise exercise-induced oxidative stress through its actions as a cysteine donor in the maintenance of glutathione homeostasis and via direct scavenging of reactive oxygen species. There are two ways in which NAC supplementation may support athlete performance, as described below:

1. NAC as an ergogenic aid to improve high intensity and repeat sprint performance
   • An accumulation of oxidants can interfere with skeletal muscle contraction¹
   • There is evidence suggesting that oral NAC supplementation may help to scavenge or ‘buffer’ oxidants and enable muscle contraction to continue during intense exercise^2-4
2. NAC to reduce exercise-induced inflammation
   • NAC has been shown to support athlete health during periods of intensified training² and tournaments³
   • Promotes the up-regulation of anti-inflammatory cytokines and minimises skeletal muscle injury following fatiguing contractile activity⁵

• NAC is available in a capsule or powder form but no batched product is currently available in Australia.

• Please refer to Table 1 for suggested supplementation protocols for the different situations that NAC can be used.
• Anecdotally, NAC is best taken with food to minimise risk of gastrointestinal distress.

Table 1: NAC supplementation protocols >

Current use of antioxidant supplements

Mega dosing with exogenous antioxidants can potentially inhibit adaptations to exercise.⁶ It is important to establish an athlete’s current use of antioxidant supplements and consider ceasing when supplementing with NAC for prolonged periods (i.e., during training camps).

Side effects of NAC

Several unwanted side effects have been reported with the use of NAC. It is recommended that when using NAC, athletes are educated on the potential side effects and complete the questionnaire below daily to track and manage any occurrences (Figure 1). If side effects do occur, quercetin may be used as an effective alternative during periods of intensified training or altitude camps. However, other ergogenic aids (i.e., bicarbonate, caffeine) should be considered if NAC is being used for acute performance benefits.

Figure 1: N-Acetyl Cysteine Health Questionnaire

Please grade any reactions that you experience following consumption of the supplement.
Mark only one square.

Habitual use is not recommended

NAC is not recommended for habitual use. Rather, an increased dietary intake of antioxidant rich foods should be used to improve the oxidantantioxidant balance in athletes.

Supplement safety information and batch tested product list
Supplements in sport | Sport Integrity Australia

1. Cobley, J. N., McGlory, C., Morton, J. P., & Close, G. L. (2011). N-Acetylcysteine Attenuates Fatigue Following Repeated-Bouts of Intermittent Exercise: Practical Implications for Tournament Situations. Int J Sport Nutr Exerc Metab.
2. Merry, T. L., & Ristow, M. (2016). Do antioxidant supplements interfere with skeletal muscle adaptation to exercise training? J Physiol, 594(18), 5135-5147.
3. Pinheiro, C. H., Vitzel, K. F., & Curi, R. (2012). Effect of N-acetylcysteine on markers of skeletal muscle injury after fatiguing contractile activity. Scand J Med Sci Sports, 22(1), 24-33.
4. Reid, M. B., Stokic, D. S., Koch, S. M., Khawli, F. A., & Leis, A. A. (1994). N-acetylcysteine inhibits muscle fatigue in humans. The Journal of Clinical Investigation, 94(6), 2468-2474.
5. Rhodes, K. M., Baker, D. F., Smith, B. T., & Braakhuis, A. J. (2019). Acute Effect of Oral N-Acetylcysteine on Muscle Soreness and Exercise Performance in Semi-Elite Rugby Players. J Diet Suppl, 16(4), 443-453.
6. Slattery, K. M., Dascombe, B., Wallace, L. K., Bentley, D. J., & Coutts, A. J. (2014). Effect of N-acetylcysteine on cycling performance after intensified training. Med Sci Sports Exerc, 46(6), 1114-1123.