11 GRAPHICS + 1 IOC TABLE – CLICK ON GRAPHIC TO ENLARGE
|Micronutrient||Overview||Diagnosis/Outcomes of Insufficiency||Protocols/Outcomes of Supplementation|
|Vitamin D||Important in regulation of gene transcription in most tissues so insufficiency/deficiency affects many body systems (Hossein-nezhad et al., 2013); many athletes are at risk of insufficiency at various times throughout the year (Larson-Meyer & Willis, 2010)||No consensus over the serum 25-hydroxyvitamin D concentration (the marker of vitamin D status) that defines deficiency, insufficiency, sufficiency, and a tolerable UL; the need to supplement depends on UVB exposure and skin type||Supplementation of between 800 IU and 1,000–2,000 IU/day is recommended to maintain status for the general population. Supplementation guidelines are not yet established in athletes. Short-term, high-dose supplementation, which includes 50,000 IU/week for 8–16 weeks or 10,000 IU/day for several weeks, may be appropriate for restoring status in deficient athletes. Careful monitoring is necessary to avoid toxicity (Heaney, 2008).|
|Iron||Suboptimal iron status may result from limited iron intake, poor bioavailability and/or inadequate energy intake, or excess iron need due to rapid growth, high-altitude training, menstrual blood loss, foot-strike hemolysis, or excess losses in sweat, urine, or feces (Thomas et al., 2016)||Several measures performed simultaneously provide the best assessment and determine the stage of deficiency; recommended measures: serum ferritin, transferrin saturation, serum iron, transferrin receptor, zinc protoporphyrin, hemoglobin, hematocrit, mean corpuscular volume (Gibson, 2005)||Athletes who do not maintain adequate iron status may need supplemental iron at doses greater than their RDA (i.e., >18 mg/day for women and >8 mg/day for men). Athletes with iron deficiency require clinical follow-up which may include supplementation with larger doses of oral iron supplementation along with improved dietary iron intake (Thomas et al., 2016). Numerous oral iron preparations are available and most are equally effective as long as they are taken (Schrier & Auerbach, 2017). High-dose iron supplements, however, should be not taken unless iron deficiency is present.|
|Calcium||Avoidance of dairy products and other calcium-rich foods, restricted energy intake, and/or disordered eating increases risk of suboptimal calcium status (Thomas et al., 2016)||No appropriate indicator of calcium status; bone mineral density scan may be indicative of chronic low calcium intake but other factors including suboptimal vitamin D status and disordered eating are also important||Calcium intakes of 1,500 mg/day and 1,500 to 2,000 IU vitamin D are recommended to optimize bone health in athletes with low energy availability or menstrual dysfunction (Thomas et al., 2016).|
Abbreviations: RDA = recommended dietary allowance; UL = upper limit; UVB = ultraviolet B.
* See Larson-Meyer et al. (2018) for additional information.
Note. Indiscriminate supplementation with any of the above nutrients is not recommended. Deficiencies should first be identified through nutritional assessment, which includes dietary intake and the appropriate blood or urinary marker, if available (Larson-Meyer et al., 2018).
|Overview||Caffeine is a stimulant that possesses well-established benefits for athletic performance across endurance-based situations, and short-term, supramaximal, and/or repeated sprint tasks.|
|Mechanism||Adenosine receptor antagonism; increased endorphin release; improved neuromuscular function; improved vigilance and alertness; reduce perception of exertion during exercise (Burke, 2008; Spriet, 2014)|
|Protocol of use||3–6 mg/kg of BM, in the form of anhydrous caffeine (i.e., pill or powder form), consumed ∼60 min prior to exercise (Ganio et al., 2009). Lower caffeine doses (<3 mg/kg BM, ∼200 mg), provided both before and during exercise; consumed with a CHO source (Spriet, 2014).|
|Performance impact||Improved endurance capacity such as exercise time to fatigue (French et al., 1991), and endurance-based TT activities of varying duration (5–150 min), across numerous exercise modalities (i.e., cycling, running, rowing, and others; Ganio et al., 2009). Low-doses of caffeine (100–300 mg) consumed during endurance exercise (after 15–80 min of activity) may enhance cycling TT performance by 3–7% (Paton et al., 2015; Talanian & Spriet, 2016). During short-term, supramaximal, and repeated sprint tasks, 3–6 mg/kg BM of caffeine taken 50–60 min before exercise results in performance gains of >3% for task completion time, mean power output, and peak power output during anaerobic activities of 1–2 min in duration (Wiles et al., 2006), and of 1–8% for total work output and repeat sprint performances during intermittent team game activity (Schneiker et al., 2006; Wellington et al., 2017).|
|Further considerations and potential side effects||Larger caffeine doses (≥9 mg/kg BM) do not appear to increase the performance benefit (Bruce et al., 2000), and are more likely to increase the risk of negative side effects, including nausea, anxiety, insomnia, and restlessness (Burke, 2008). Lower caffeine doses, variations in the timing of intake before and/or during exercise, and the need for (or lack thereof) a caffeine withdrawal period should be trialed in training prior to competition use. Caffeine consumption during activity should be considered concurrent with CHO intake for improved efficacy (Talanian & Spriet, 2016). Caffeine is a diuretic, promoting increased urine flow, but this effect is small at the doses that have been shown to enhance performance (Maughan & Griffin, 2003).|
|Overview||Creatine loading can acutely enhance the performance of sports involving repeated high-intensity exercise (e.g., team sports), as well as the chronic outcomes of training programs based on these characteristics (e.g., resistance or interval training), leading to greater gains in lean mass and muscular strength and power (Rawson & Persky, 2007; Volek & Rawson, 2004).|
|Mechanism||Supplementation increases muscle creatine stores, augmenting the rate of PCr resynthesis, thereby enhancing short-term, high-intensity exercise capacity (Buford et al., 2007) and the ability to perform repeated bouts of high-intensity effort.|
|Protocol of use||Loading-phase: ∼20 g/day (divided into 4 equal daily doses), for 5–7 days (Lanhers et al., 2017)
Maintenance-phase: 3–5 g/day (single dose) for the duration of the supplementation period (Hultman et al., 1996).
Note: Concurrent consumption with a mixed protein/CHO source (∼50 g of protein and CHO) may enhance muscle creatine uptake via insulin stimulation (Steenge et al., 2000).
|Performance impact||Enhanced maximum isometric strength (Maganaris & Maughan, 1998) and the acute performance of single and repeated bouts of high-intensity exercise (<150 s duration); most pronounced effects evident during tasks <30 s (Branch, 2003; Lanhers et al., 2017). Chronic training adaptations include lean mass gains and improvements to muscular strength and power (Rawson & Persky, 2007; Volek & Rawson, 2004). Less common: Enhanced endurance performance resulting from increased/improved protein synthesis, glycogen storage, and thermoregulation (Cooper et al., 2012; Kreider et al., 2017). Potential anti-inflammatory and anti-oxidant effects are noted (Deminice et al., 2013).|
|Further considerations and potential side effects||No negative health effects are noted with long-term use (up to 4 years) when appropriate loading protocols are followed (Schilling et al., 2001). A potential 1–2 kg BM increase after creatine loading (primarily as a result of water retention; Deminice et al., 2013; Powers et al., 2003), may be detrimental for endurance performance or in events where the BM must be moved against gravity (e.g., high jump, pole vault) or where athletes must achieve a specific BM target.|
|Overview||Dietary nitrate (NO3–) is a popular supplement that has been commonly investigated to assess any benefits for prolonged submaximal exercise (Bailey et al., 2009) and high-intensity, intermittent, short-duration efforts (Thompson et al., 2015; Wylie et al., 2016).|
|Mechanism||Enhances nitric oxide (NO) bioavailability via the NO3-nitrite-NO pathway, playing an important role in the modulation of skeletal muscle function (Jones, 2014a). Nitrate augments exercise performance via an enhanced function of type II muscle fibers (Bailey et al., 2015); a reduced ATP cost of muscle force production; an increased efficiency of mitochondrial respiration; an increased blood flow to the muscle; a decrease in blood flow to VO2 heterogeneities (Bailey et al., 2010).|
|Protocol of use||High nitrate containing foods include leafy green and root vegetables, including spinach, rocket salad, celery, and beetroot. Acute performance benefits are generally seen within 2–3 hr following a NO3– bolus of 5–9 mmol (310–560 mg) (Hoon et al., 2014). Prolonged periods of NO3– intake (>3 days) also appears beneficial to performance (Thompson et al., 2015, 2016), and may be a positive strategy for highly-trained athletes, where performance gains from NO3– supplementation appear harder to obtain (Jones, 2014b).|
|Performance impact||Supplementation has been associated with improvements of 4–25% in exercise time to exhaustion and of 1–3% in sport-specific TT performances lasting <40 min in duration (Bailey et al., 2015; McMahon et al., 2016). Supplementation is proposed to enhance type II muscle fiber function (Bailey et al., 2015), resulting in the improvement (3–5%) of high-intensity, intermittent, team-sport exercise of 12–40 min in duration (Thompson et al., 2015; Wylie et al., 2016). Evidence is equivocal for any benefit to exercise tasks lasting <12 min (Reynolds et al., 2016; Thompson et al., 2016).|
|Further considerations and potential side effects||The available evidence suggests there appears to be few side effects or limitations to nitrate supplementation. There may exist the potential for GI upset in susceptible athletes, and should therefore be thoroughly trialed in training. There appears to be an upper limit to the benefits of consumption (i.e., no greater benefit from 16.8 mmol [1,041 mg] vs. 8.4 mmol [521 mg]; Wylie et al., 2013). Performance gains appear harder to obtain in highly-trained athletes (Jones, 2014b).|
|Overview||Beta-alanine augments intracellular buffering capacity, having potential beneficial effects on sustained high-intensity exercise performance.|
|Mechanism||A rate-limiting precursor to the endogenous intracellular (muscle) buffer, carnosine; the immediate defense against proton accumulation in the contracting musculature during exercise (Lancha Junior et al., 2015). Chronic, daily supplementation of beta-alanine increases skeletal muscle carnosine content (Saunders et al., 2016).|
|Protocol of use||Daily consumption of ∼65 mg/kg BM, ingested via a split-dose regimen (i.e., 0.8–1.6 g every 3–4 hr) over an extended supplement time frame of 10–12 weeks (Saunders et al., 2016).|
|Performance Impact||Small but potentially meaningful performance benefits (∼0.2–3%) during both continuous and intermittent exercise tasks of 30 s to 10 min in duration (Baguet et al., 2010; Chung et al., 2012; Saunders et al., 2016).|
|Further considerations and potential side effects||A positive correlation between the magnitude of muscle carnosine change and performance benefit remains to be established (Saunders et al., 2016). Large interindividual variations in muscle carnosine synthesis have been reported (Nassis et al., 2016). The supplement effectiveness appears harder to realize in well-trained athletes (Bellinger, 2014). There is a need for further investigation to establish the practical use in various sport-specific situations (Hobson et al., 2012; Saunders et al., 2016). Possible negative side effects include skin rashes and/or transient paresthesia.|
|Overview||Sodium bicarbonate augments extracellular buffering capacity, having potential beneficial effects on sustained high-intensity exercise performance.|
|Mechanism||Acts as an extracellular (blood) buffer, aiding intracellular pH regulation by raising the extracellular pH, and HCO3- concentrations (Katz et al., 1984; Lancha Junior et al., 2015). The resultant pH gradient between the intracellular and extracellular environments leads to efflux of H+ and La- from the exercising muscle (Katz et al., 1984; Mainwood et al., 1975).|
|Protocol of use||Single acute NaHCO3 dose of 0.2–0.4 g/kg BM, consumed 60–150 min prior to exercise (Carr et al., 2011b; Siegler et al., 2012) Alternative strategies include: split doses (i.e., several smaller doses giving the same total intake) taken over a 30–180 min time period (Lambert et al., 1993); serial-loading with 3–4 smaller doses per day for 2–4 consecutive days prior to an event (Burke, 2013; Douroudos et al., 2006; Mc Naughton & Thompson, 2001).|
|Performance impact||Enhanced performance (∼2%) of short-term, high-intensity sprints lasting ∼60 s in duration, with a reduced efficacy as the effort duration exceeds 10 min (Carr et al., 2011b).|
|Further considerations and potential side effects||Well-established GI distress may be associated with this supplement. Strategies to minimize GI upset include: co-ingestion with a small, carbohydrate-rich meal (∼1.5 g/kg BM carbohydrates) (Carr et al., 2011c); the use of sodium citrate as an alternative (Requena et al., 2005); split-dose or stacking strategies (Burke, 2013; Douroudos et al., 2006; Mc Naughton & Thompson, 2001). Given the high potential for GI distress, thorough investigation into the best individualized strategy is recommended prior to use in a competition setting.|
|Supplement||Proposed Mechanism of Action||Evidence for Efficacy|
|Vitamin D||An essential fat-soluble vitamin known to influence several aspects of immunity, particularly innate immunity (e.g., expression of antimicrobial proteins). Skin exposure to sunlight accounts for 90% of the source of vitamin D.||Moderate support. Evidence for deficiency in some athletes and soldiers, particularly in the winter (decreased skin sunlight exposure). Deficiency has been associated with increased URS. Recommend 1,000 IU/day D3 autumn–spring to maintain sufficiency. Further support required (He et al., 2016).|
|Probiotics||Probiotics are live microorganisms which, when administered orally for several weeks, can increase the numbers of beneficial bacteria in the gut. This has been associated with a range of potential benefits to gut health, as well as modulation of immune function.||Moderate support in athletes with daily dose of ∼1010 live bacteria; Cochrane review of 12 studies (n = 3,720) shows ∼50% decrease in URS incidence and ∼2 day shortening of URS; minor side effects. More evidence is required supporting efficacy to reduce gastrointestinal distress and infection (e.g., in a traveling athlete; Gleeson et al., 2011; Hao et al., 2015).|
|Vitamin C||An essential water-soluble antioxidant vitamin that quenches ROS and augments immunity. Reduces interleukin-6 and cortisol responses to exercise in humans.||Moderate support for preventing URS. Cochrane review of 5 studies in heavy exercisers (n = 598) shows ∼50% decrease in URS taking vitamin C (0.25–1.0 g/day). Further support required. Unclear if antioxidants blunt adaptation in well-trained. Relatively small effects on cortisol compared with carbohydrate; immune measures no different from placebo. No support for treating URS. Cochrane reviews show no benefit of initiating vitamin C supplementation (>200 mg/day) after onset of URS (Hemila & Chalker, 2013; Nieman et al., 2002).|
|Carbohydrate (drinks, gels)||Maintains blood glucose during exercise, lowers stress hormones, and thus counters immune dysfunction.||Low-moderate support. Ingestion of carbohydrate (30–60 g/hr) attenuates stress hormone and some, but not all, immune perturbations during exercise. Very limited evidence that this modifies infection risk in athletes (Bermon et al., 2017; Walsh et al., 2011).|
|Bovine colostrum||First milk of the cow that contains antibodies, growth factors, and cytokines. Claimed to improve mucosal immunity and increase resistance to infection.||Low-moderate support that bovine colostrum blunts the decrease in saliva antimicrobial proteins after heavy exercise. Some evidence in small numbers of participants that bovine colostrum decreases URS. Further support required (Brinkworth & Buckley, 2003; Davison & Diment, 2010).|
|Polyphenols (e.g., Quercetin)||Plant flavonoids. In vitro studies show strong anti-inflammatory, anti-oxidant, and anti-pathogenic effects. Animal data indicate an increase in mitochondrial biogenesis and endurance performance.||Low-moderate support. Human studies show some reduction in URS during short periods of intensified training and mild stimulation of mitochondrial biogenesis and endurance performance, albeit in small numbers of untrained subjects. Limited influence on markers of immunity. Putative anti-viral effect for Quercetin. Further support required (Gleeson, 2016; Nieman et al., 2007).|
|Zinc||An essential mineral that is claimed to reduce incidence and duration of colds. Zinc is required for DNA synthesis and as an enzyme cofactor for immune cells. Zinc deficiency results in impaired immunity (e.g., lymphoid atrophy), and zinc deficiency is not uncommon in athletes.||No support for preventing URS. High doses of zinc can decrease immune function and should be avoided. Moderate support for treating URS. Cochrane review shows benefit of zinc acetate lozenges (75 mg) to decrease duration of URS; however, zinc must be taken <24 hr after onset of URS for duration of cold only. Side effects include bad taste and nausea (Singh & Das, 2013).|
|Glutamine||Nonessential amino acid that is an important energy substrate for immune cells, particularly lymphocytes. Circulating glutamine is lowered after prolonged exercise and very heavy training.||Limited support. Supplementation before and after exercise does not alter immune perturbations. Some evidence of a reduction in URS after endurance events in competitors receiving glutamine supplementation (2 × 5 g). Mechanism for therapeutic effect requires investigation (Castell et al., 1996; Walsh et al., 1998).|
|Caffeine||Stimulant found in a variety of foods and drinks (e.g., coffee and sports drinks). Caffeine is an adenosine receptor antagonist and immune cells express adenosine receptors.||Limited support. Evidence that caffeine supplementation activates lymphocytes and attenuates the fall in neutrophil function after exercise. Efficacy for altering URS in athletes remains unknown (Dulson & Bishop, 2016; Walker et al., 2007).|
|Echinacea||Herbal extract claimed to enhance immunity via stimulatory effects on macrophages. There is some in vitro evidence for this.||Limited support. Early human studies indicated possible beneficial effects but more recent, larger scale, and better controlled studies indicate no effect of Echinacea on infection incidence or cold symptom severity (Karsch-Volk et al., 2015; Linde et al., 2006).|
|Omega-3 PUFAs||Found in fish oil. May influence immune function by acting as a fuel, in their role as membrane constituents or by regulating eicosanoid formation (e.g., prostaglandin). Prostaglandin is immunosuppressive. Claimed to exert anti-inflammatory effects postexercise.||Limited support for blunting inflammation and functional changes after muscle-damaging eccentric exercise in humans and no evidence of reducing URS in athletes (Jakeman et al., 2017; Mickleborough, 2013).|
|Vitamin E||An essential fat-soluble antioxidant vitamin that quenches exercise-induced ROS and augments immunity.||No support. Immune-enhancing effects in the frail elderly but no benefit in young, healthy humans. One study actually showed that vitamin E supplementation increased URS in those under heavy exertion. High doses may be pro-oxidative (Hemila et al., 2003; Meydani et al., 2004).|
|β-glucans||Polysaccharides derived from the cell walls of yeast, fungi, algae, and oats that stimulate innate immunity.||No support in humans. Effective in mice inoculated with influenza virus; however, human studies with athletes show no benefits (Nieman et al., 2008; Volman et al., 2008).|
|Supplement||+||Evidence for Efficacy|
– Creatine is a naturally occurring nutrient, consumed in the diet, and synthesized in the body
– Recommended supplement dose is 20 g/day for 5 days, followed by 3 to 5 g/day to increase and maintain elevated body creatine levels (Harris et al., 1992; Hultman et al., 1996).
|+||– Many studies demonstrate improved training adaptations, such as increased lean mass or strength, indicating an enhanced adaptive response to exercise (Branch, 2003; Heaton et al., 2017; Rawson & Volek, 2003)
– Reduced symptoms of, or enhanced recovery from, muscle-damaging exercise (e.g., DOMS) have been reported in some, but not all studies (reviewed in (Rawson et al., 2017)
– Enhanced recovery from disuse or immobilization/extreme inactivity has been reported in some, but not all studies (reviewed in Heaton et al., 2017)
– Improved cognitive processing is reported in most studies, especially when volunteers were fatigued by sleep deprivation or mental/physical tasks (reviewed in Gualano et al., 2012; 2016; Rae & Broer, 2015; Rawson & Venezia, 2011)
– The effects in athletes have not been well characterized, and only one group attempted to translate these effects into to athletic performance, albeit with a positive result. (Cook 2011)
– Decreased damage and enhanced recovery from mTBI is supported by open label trials in children (Sakellaris et al., 2006, 2008) and using animal models (Sullivan et al., 2000); 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.
|+||– Beneficial effects of HMB on strength and fat free mass are small, while the effects on muscle damage are unclear (Rowlands & Thomson, 2009)
– Recent reports of “steroid-like” gains in strength, power, and fat free mass, and reductions in muscle damage from HMB-free acid (HMB-FA) supplementation (Lowery et al., 2016; Wilson et al., 2013, 2014) have not been reproduced and seem unlikely (Phillips et al., 2017)
– 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 (Deutz et al., 2013)
– Benefits of HMB supplementation could most likely be obtained from normal dietary protein or whole protein supplements (Wilkinson et al., 2013), 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 following omega 3-fatty acid supplementation shown in healthy older adults with mild or severe cognitive impairment (reviewed in Barrett et al., 2014)
– 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 Barrett et al., 2014; Erdman et al., 2011; Tipton, 2015)
– Two case studies support these findings (Lewis et al., 2013; Roberts et al., 2008) and large, double-blind, placebo-controlled trials are currently under way (clinicaltrials.gov NCT101903525, NCT01814527)
– In muscle, omega-3 fatty acid supplementation can increase muscle protein synthesis (Smith et al., 2011a, 2011b), but this may not occur when protein is ingested after exercise in recommended amounts (Smith et al., 2011a, 2011b)
– Anti-inflammatory effects of omega-3 fatty acid intake may reduce muscle damage or enhance recovery from intense, eccentric exercise (e.g., decrease DOMS), but this is not a consistent finding (Gray et al., 2014; Jouris et al., 2011)
– No indication that decreased omega 3-fatty acids in the body impair performance, and high-dose supplements can cause some adverse effects (reviewed in (Erdman et al., 2011; Mickleborough, 2013), 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.
– An essential fat-soluble vitamin. Skin exposure to sunlight normally accounts for 90% of the source of vitamin D.
|+||– 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 (Close et al., 2013, 2016; Owens et al., 2014, 2015)
– 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 (Ruohola et al., 2006)
– US Naval recruits supplemented with 800 IU/day of vitamin D3 and 2,000 mg calcium reduced stress fracture incidence by 20% (Lappe et al., 2008)
– 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 to 15 g gelatin with 50 mg vitamin C (Shaw 2017). Collagen hydrolysate dose is about 10 g/day (Clark 2008; McAlindon 2011)
|+||– Gelatin and collagen supplements appear to be low risk
– Few data available (Clark et al., 2008; McAlindon et al., 2011; Shaw et al., 2017) but increased collagen production and decreased pain seem possible
– Functional benefits, recovery from injury, and effects in elite athletes are not known.
– Curcumin (a constituent of turmeric) is ingested for anti-inflammatory effects at a dose of about 5 g/day
– Tart cherry juice about 250–350 mL (30 mL if concentrate) twice daily for 4 to 5 days before an athletic event or for 2 to 3 days after to promote recovery
|+||– Decreases in inflammatory cytokines and/or indirect markers of muscle damage with anti-inflammatory supplements such as curcumin (McFarlin 2016; Nicol et al., 2015; Sciberras 2015) and tart cherry juice (reviewed in Bell 2014; Coelho Rabello Lima 2015) 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.
|Supplement||Proposed Mechanism of Action||Evidence for Efficacy|
|Gaining lean body mass*|
Recommended daily dose: 1.6 g protein/kg/day optimal (up to 2.2 g/kg/day with no adverse effects)
Recommended per-meal doses: 0.3–0.5 g protein/kg (4-5x per day with one in close proximity to exercise, with postexercise being consistently shown to be effective)
|Enhances lean mass gains when ingested during programs of resistance training due to increased building blocks (amino acids) and leucine as a trigger for a rise in muscle protein synthesis and suppression of muscle protein breakdown||Meta-analyses focusing on younger and older participants have shown positive effects enhancing gains in muscle mass (Cermak 2012; Morton 2017), but effects are not large|
|Leucine||Stimulates muscle protein synthesis and suppresses protein breakdown (possibly through insulin)||Short-term mechanistic data available (Wilkinson 2013), but no long-term trials showing efficacy (Aguiar 2017)|
|Losing fat mass**|
From increased dietary sources or supplemental isolated proteins
|Enhance fat mass loss and promotes retention of lean mass||Meta-analyses confirm small but significant effects of protein in wt loss to enhance fat mass loss and promote lean mass retention (Krieger, 2006; Wycherley 2012)|
|Pyruvate||No data||Small-to-trivial effect (Onakpoya et al., 2014a)|
|Chromium||Potentiates biological actions of insulin||No effect (Tian et al., 2013)|
|Green tea (polyphenol catechins and caffeine)||Thermogenic agent and/or lipolytic-enhancing agent||Small-to-trivial effect (Jurgens et al., 2012)|
|α-Lipoic acid||No clear role, but possible antioxidant||Small-to-trivial effect (Kucukgoncu et al., 2017)|
|Conjugated linoleic acid (CLA)||Changes membrane fluidity favoring enhanced fat oxidation||Small-to-trivial effect (Onakpoya et al., 2012)|
|Konjac fiber (glucomannan)||Water-soluble polysaccharide—dietary fiber||Small-to-trivial effect (Onakpoya et al., 2014b)|
|Omega-3 polyunsaturated fatty acids||No clear role, but possible appetite suppression, improved blood flow, and/or modulator of gene expression||Small-to-trivial effect (Zhang et al., 2017)|
|Chitosan||Lipid-binding agent to reduce lipid absorption||Small-to-trivial effect (Jull et al., 2008)|