Table 5.

Supplements that may assist with training capacity, recovery, muscle soreness and injury management

Supplement	Proposed mechanism of action	Evidence for efficacy41
Creatine monohydrate Creatine is a naturally occurring nutrient, consumed in the diet and synthesised in the body. Recommended supplement dose is 20 g/day for 5 days, followed by 3–5 g/day to increase and maintain elevated body creatine levels.119 120	Enhanced adaptive response to exercise via increased growth factor/gene expression and increased intracellular water Reduced symptoms of, or enhanced recovery from, muscle damaging exercise (eg, DOMS) Enhanced recovery from disuse or immobilisation/extreme inactivity Improved cognitive processing Decreased risk/enhanced recovery from mTBI	Many studies demonstrate improved training adaptations, such as increased lean mass or strength, indicating an enhanced adaptive response to exercise.12 13 121 Reduced symptoms of, or enhanced recovery from, muscle damaging exercise (eg, DOMS) have been reported in some, but not all studies (reviewed in ref 122). Enhanced recovery from disuse or immobilisation/extreme inactivity has been reported in some, but not all studies (reviewed in ref 12). Improved cognitive processing is reported in most studies, especially when volunteers were fatigued by sleep deprivation or mental/physical tasks (reviewed in refs 11 123–125). The effects in athletes have not been well-characterised, and only one group attempted to translate these effects to athletic performance, although with a positive result.126 Decreased damage and enhanced recovery from mTBI are supported by open-label trials in children127 128 and using animal models.129 These data are not conclusive and more research is warranted. However, athletes at risk for concussion, who already ingest creatine supplements for performance or muscular benefits, may receive important brain benefits as well. A small increase in body mass is common with supplementation. This may be relevant for sports with weight classes/restrictions or where increased body mass may decrease performance.
Beta-hydroxy beta-methylbutyrate (HMB) HMB is a metabolite of the amino acid leucine. Manufacturer-recommended dosage is 3 g/day.	Enhanced adaptive response to exercise via decreased protein breakdown, increased protein synthesis, increased cholesterol synthesis, increased growth hormone and IGF-I mRNA, increased proliferation and differentiation of satellite cells and inhibited apoptosis (reviewed in ref 130)	Beneficial effects of HMB on strength and fat-free mass are small, while the effects on muscle damage are unclear.131 Recent reports of ‘steroid like’ gains in strength, power and fat-free mass, and reductions in muscle damage from HMB-free acid supplementation,132–134 have not been reproduced and seem unlikely.135 Potential use for HMB during extreme inactivity/disuse or recovery from injury, but these effects have only been described in older adults following 10 days of bed rest.136 Benefits of HMB supplementation could most likely be obtained from normal dietary protein or whole protein supplements,137 so HMB supplements may not be more effective than adhering to the current protein intake recommendations.
Omega-3 fatty acids About 2 g/day	Improved cognitive processing Decreased risk/enhanced recovery from mTBI Increased muscle protein synthesis Reduced symptoms of, or enhanced recovery from, muscle damaging exercise (eg, DOMS)	Improved cognitive processing following omega-3 fatty acid supplementation shown in healthy older adult  with mild or severe cognitive impairment (reviewed in ref 138). It is not known if these benefits would occur in young, healthy athletes, or how this would translate to athletic performance. Animal data show that the structural damage and cognitive decline associated with mTBI are reduced/attenuated with omega-3 fatty acid supplementation when ingested either before or after the injury (reviewed in refs 138–140). Two case studies support these findings,141 142 and large, double-blind, placebo-controlled trials are currently under way (ClinicalTrials.gov NCT101903525 and  NCT01814527). In muscle, omega-3 fatty acid supplementation can increase muscle protein synthesis,143 144 but this may not occur when protein is ingested after exercise in recommended amounts.143 144 Anti-inflammatory effects of omega-3 fatty acid intake may reduce muscle damage or enhance recovery from intense, eccentric exercise (eg, decrease DOMS), but this is not a consistent finding.145 146 No indication that decreased omega-3 fatty acids in the body impair performance, and high-dose supplements can cause some adverse effects (reviewed in refs 114 139), so the best recommendation may be to include rich sources of omega-3 fatty acids, such as fatty fish, in the diet instead of supplements. Low risk but unclear if supplementation should be pursued by athletes, in lieu of including fatty fish in the diet as a source of omega-3 fatty acids. Fish oil or omega-3 fatty acid supplement consumption could include heavy metal contaminants, or cause bleeding, digestive problems and/or increased LDL.
Vitamin D An essential fat-soluble vitamin Skin exposure to sunlight normally accounts for 90% of the source of vitamin D.	Enhanced adaptive response to exercise Decreased stress fractures	Data on the effects of vitamin D supplementation on muscle function and recovery are equivocal, with discrepancies likely explained by differences in baseline vitamin D concentrations prior to supplementation.147–150 Collectively, these data strongly suggest a role for adequate vitamin D in the adaptive process to stressful exercise. Low vitamin D status is associated with a 3.6× higher stress fracture risk in Finnish military recruits.151 US Naval recruits supplemented with 800 IU/day of vitamin D3 and 2000 mg calcium reduced stress fracture incidence by 20%.152 More data are needed, but it appears that vitamin D status relates to stress fracture risk, and supplementation, when warranted, may reduce this risk.
Gelatin and vitamin C/collagen Recommended dose is 5–15 g gelatin with 50 mg vitamin C.153 Collagen hydrolysate dose is about 10 g/day.154 155	Increased collagen production Thickened cartilage Decreased joint pain	Gelatin and collagen supplements appear to be low risk. Few data available,153–155 but increased collagen production and decreased pain seem possible. Functional benefits, recovery from injury, and effects in elite athletes are not known.
Anti-inflammatory supplements Curcumin (a constituent of the spice turmeric) is often ingested for anti-inflammatory effects at a dose of about 5 g/day. Tart cherry juice at a dose of about 250–350 mL (30 mL if concentrate) twice daily for 4–5 days before an athletic event or for 2–3 days afterwards to promote recovery	Anti-inflammatory effects Reduced symptoms of, or enhanced recovery, from muscle damaging exercise (eg, DOMS)	Decreases in inflammatory cytokines and/or indirect markers of muscle damage with anti-inflammatory supplements such as curcumin156–158 and tart cherry juice (reviewed in refs 159 160) have been reported. Anti-inflammatory effects may be beneficial, although benefits may be sport/training-specific. More research is needed before these compounds can be recommended to athletes.

DOMS, delayed-onset muscle soreness; mTBI, mild traumatic brain injury (concussion).