Although consuming beetroot juice concentrate on each of 4 days to supply 4. However, consumption of even more beetroot juice supplying There has been little study of the effects of beetroot on anaerobic performance, such as high-volume resistance exercise with many repetitions [ 40 ].

More research is needed to clarify the potential benefits of nitrate supplementation from beetroot juice on exercise and athletic performance and to determine the best doses and dosing protocols [ 48 ]. No research has assessed longer term supplementation with beetroot-derived nitrate beyond several weeks as an ergogenic aid.

The amount of nitrate that this amount of juice provides is less than half the total nitrate consumption from a diet rich in vegetables and fruits [ 49 ].

Although not a safety concern, beetroot consumption can color the urine pink or red due to the excretion of red pigments in the beets [ 50 ]. In a position statement, the Academy of Nutrition and Dietetics AND , the Dietitians of Canada DoC , and the American College of Sports Medicine ACSM state that nitrate sources, such as beetroot juice, enhance exercise tolerance and economy and they improve endurance exercise performance in recreational athletes [ 12 ].

The Australian Institute of Sport supports the use of beetroot juice for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how the supplement should be used for best results [ 29 ].

This amount of juice provides about 5—11 mmol or — mg nitrate, depending on the product [ 41 ]. Potential benefits persist for up to 24 hours after ingestion [ 40 ]. The labels on beetroot juice and concentrate usually indicate that these products are foods and not dietary supplements.

Some dietary supplements contain beetroot powder in varying amounts, but studies have not assessed whether these are viable alternatives to beetroot juice or beetroot-juice concentrate. Beta-alanine, a type of amino acid that the body does not incorporate into proteins, is the rate-limiting precursor to the synthesis of carnosine—a dipeptide of histidine and beta-alanine—in skeletal muscle.

Carnosine helps buffer changes in muscle pH from the anaerobic glycolysis that provides energy during high-intensity exercise but results in the buildup of hydrogen ions as lactic acid accumulates and dissociates to form lactate, leading to reduced force and to fatigue [ 51 ].

More carnosine in muscle leads to greater potential attenuation of exercise-induced reductions in pH, which could enhance performance of intense activities of short to moderate duration, such as rowing and swimming [ 52 ].

Beta-alanine is produced in the liver, and relatively small amounts are present in animal-based foods such as meat, poultry, and fish. Carnosine is present in animal-based foods, such as beef and pork. However, oral consumption of carnosine is an inefficient method of increasing muscle carnosine concentrations because the dipeptide is digested into its constituent amino acids.

Consumption of beta-alanine, in contrast, reliably increases the amount of carnosine in the body. For example, in one study of young, physically active but untrained adult men who took 4. Among the low responders, the duration of the washout period when beta alanine concentrations returned to baseline values was less than half that for the high responders 6 weeks vs.

Studies have evaluated beta-alanine as a potential ergogenic aid with a variety of participants, exercise and activity protocols, and dosing regimens.

Some studies suggest that beta-alanine consumption could provide small performance benefits in competitive events requiring high-intensity effort over a short period, such as rowing, swimming, and team sports e. Other studies have found no such benefits [ 53 ]. Evidence is conflicting on whether beta-alanine consumption improves performance in endurance activities, such as cycling [ 53 , 56 ].

Experts have not reached consensus on whether beta-alanine consumption primarily benefits trained athletes or recreationally active individuals [ 53 , 57 ].

Studies provide little consistent evidence of a relationship between the dose of beta-alanine and performance effect [ 51 , 58 ]. The authors of a Department of Defense-sponsored review concluded that the limited evidence from 20 human trials did not support consumption of beta-alanine alone or in combination products by active adults to enhance athletic performance or improve recovery from exercise-related exhaustion [ 59 ].

Most of the studies in this review included young men age 18—25 years who took 1. However, performance benefits are more modest in exercise tests lasting more than 4 minutes because aerobic metabolic pathways increasingly meet energy demands.

The ISSN called for more research to determine whether beta-alanine increases the strength and muscle mass that regular resistance exercise, such as weightlifting, can produce. The authors of the most recent review of studies on beta-alanine's effects on exercise concluded that supplementation has a statistically significant and positive effect on performance including in both isolated-limb and whole-body exercises , especially in protocols lasting 30 seconds to 10 minutes [ 58 ].

However, this review also highlighted the fact that small studies of short duration using varied exercise and supplement protocols dominate this scientific literature. The 40 placebo-controlled studies reviewed, for example, employed 65 exercise protocols and 70 exercise measures in a total of 1, participants.

Furthermore, the total dose of beta-alanine that participants consumed ranged from 84 to g in studies lasting 28—90 days. Beta-alanine supplementation appears to be safe at 1. This tingling, prickling, or burning sensation is common in the face, neck, back of the hands, and upper trunk and typically lasts 60—90 minutes but is not a painful, serious, or harmful reaction.

Use of divided doses or a sustained-release form of the supplement can attenuate paresthesia resulting from beta-alanine consumption [ 52 , 54 ]. Some research has also found that beta-alanine supplements can produce pruritus itchy skin , but the authors do not indicate the severity of this effect [ 59 ].

There are no safety data on use of the supplement for more than 1 year [ 54 , 60 ]. There is insufficient expert consensus on the value of taking beta-alanine to enhance performance in intense, short-term activities or its safety, particularly when users take it regularly for at least several months.

In a position statement, the AND, DoC, and ACSM advise that beta-alanine supplementation might improve training capacity and does enhance performance, especially of high-intensity exercise lasting 60— seconds, that acid-base disturbances resulting from increased anaerobic glycolysis would otherwise impair [ 12 ].

In its position statement, the ISSN concludes that beta-alanine supplementation improves exercise performance and attenuates neuromuscular fatigue [ 54 ]. The Australian Institute of Sport supports the use of beta-alanine for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how the supplement should be used for best results [ 29 ].

It advises users to take beta-alanine supplements with meals to augment muscle carnosine levels and to use divided lower doses or take a sustained-release form if paresthesia occurs.

HMB is a metabolite of the branched-chain amino acid leucine. Some experts hypothesize that skeletal muscle cells that become stressed and damaged from exercise require an exogenous source of the coenzyme for synthesis of cholesterol in their cellular membranes to restore structure and function [ 62 , 63 ].

Experts also believe that the conversion of leucine to HMB activates muscle protein synthesis and reduces protein breakdown [ 63 ].

Although studies have investigated HMB for two decades, they have used substantially different periods of supplementation 1 day to 6 weeks and daily doses 1. Studies also used participants of different ages 19 to 50 years , training status e. It is therefore difficult to predict what, if any, benefits an exercising individual might experience from consuming HMB.

There is general agreement that HMB helps speed up recovery from exercise of sufficient amount and intensity to induce skeletal muscle damage [ 63 , 65 ]. Therefore, trained athletes must exert themselves more than untrained individuals to potentially benefit from using the supplement.

Some studies suggest that HMB use has additional benefits, including an ability to enhance strength, power, skeletal muscle hypertrophy, and aerobic performance in both trained and untrained people [ 63 ].

A review of safety data from nine studies found that users tolerate HMB well, and it is safe at daily intakes of 3 g for 3 to 8 weeks in younger ages 18—47 years and older ages 62—81 adults of both sexes who do or do not exercise [ 66 ].

Assessments of blood chemistry, hematology, and emotional affect found no adverse effects. Use of HMB did not alter or adversely affect any measured hematologic, hepatic, or renal-function parameters in these young men. There is no expert consensus on the value of taking HMB for several months or longer or its safety.

HMB is not on a list of evidence-based ergogenic aids issued by the AND, DoC, and the ACSM [ 12 ]. The Australian Institute of Sport does not recommend HMB supplementation by athletes, except as part of a research protocol or with proper monitoring [ 29 ].

However, the ISSN notes that HMB can enhance recovery by reducing exercise-induced skeletal muscle damage in both trained and untrained individuals [ 63 ]. HMB is available in two forms: as a mono-hydrated calcium salt HMB-Ca and a calcium-free form HMB-free acid [HMB-FA].

Those who wish to limit their calcium intake can use HMB-FA [ 63 ]. Although the latter form appears to have a faster and greater effect based on its ability to raise HMB plasma levels, more studies are needed to compare the effects of HMB-Ca with those of HMB-FA [ 63 ].

The ISSN recommends that healthy adults interested in using HMB supplements take 1—2 g HMB-Ca 60 to minutes before exercise or 1—2 g HMB-FA 30 to 60 minutes before exercise [ 63 ]. Betaine, also known as trimethylglycine, is found in foods such as beets, spinach, and whole-grain breads.

The mechanisms by which betaine might enhance exercise and athletic performance are not known, but many are hypothesized. A limited number of small studies in men have assessed betaine in supplemental form as a potential ergogenic aid. These studies, which typically examined strength- and power-based performance in bodybuilders and, occasionally, cyclists, provided conflicting results, and performance improvements tended to be modest [ ].

The several small studies of athletes described in the previous paragraph who took betaine supplements for up to several weeks found no side effects or safety concerns.

However, research has not adequately evaluated the safety of betaine. More research on betaine supplementation to enhance various types of performance, training protocols, and exercise during specific sports is needed before any recommendations for its use can be made [ 71 ].

Three essential amino acids EAAs —leucine, isoleucine, and valine—are the branched-chain amino acids BCAAs , whose name reflects their chemical structure. Unlike other EAAs, the BCAAs can be metabolized by mitochondria in skeletal muscle to provide energy during exercise [ 74 , 75 ].

The BCAAs, especially leucine, might also stimulate protein synthesis in exercised muscle [ 72 , 76 ]. The limited research on the potential ergogenic effects of the BCAAs has found little evidence to date that supplements of these amino acids improve performance in endurance-related aerobic events [ 75 ].

The BCAAs might delay feelings of fatigue or help maintain mental focus by competing with the amino acid tryptophan a precursor of the neurotransmitter serotonin that regulates mood and sleep for entry into the brain, but this effect has not been well studied [ 72 , 74 , 75 ].

Overall, however, studies to date provide inconsistent evidence of the ability of BCAAs to stimulate muscle protein synthesis beyond the capacity of sufficient dietary amounts of any high-quality protein to perform this function [ 76 ].

Furthermore, it is not clear from existing research whether consumption of protein and BCAAs before versus after a workout affects their ability to maximize muscle protein synthesis and reduce protein catabolism [ 12 , ].

Studies have not consistently shown that taking supplements of BCAAs or any of their three constituent amino acids singly enhances exercise and athletic performance, builds muscle mass, or aids in recovery from exercise. Consuming animal foods containing complete proteins—or a combination of plant-based foods with complementary proteins that together provide all EAAs—automatically increases consumption of BCAAs see section on protein.

This is also true of consuming protein powders made from complete proteins, especially whey, which has more leucine than either casein or soy [ 78 ]. Caffeine stimulates the central nervous system, muscles, and other organs such as the heart by binding to adenosine receptors on cells, thereby blocking the activity of adenosine, a neuromodulator with sedative-like properties [ 83 , 84 ].

In this way, caffeine enhances arousal, increases vigor, and reduces fatigue [ 13 , 85 , 86 ]. Caffeine also appears to reduce perceived pain and exertion [ 13 , 85 ]. During the early stages of endurance exercise, caffeine might mobilize free fatty acids as a source of energy and spare muscle glycogen [ 38 ].

Caffeine is commonly used in energy drinks and shots touted for their performance-enhancement effects [ 87 , 88 ]. It is also found in energy gels containing carbohydrates and electrolytes as well as in anhydrous caffeine-only pills.

For an individual weighing pounds 70 kg , this dose is equivalent to — mg caffeine. Taking more, however, is unlikely to improve performance further and increases the risk of side effects.

A review of the literature found that caffeine intake affected sport-specific performance e. Although 30 of the 33 trials showed positive improvements in performance, the improvements were not statistically significant in half of them [ 85 ].

In these studies, performance improvement ranged from a decrease of 0. Factors such as the timing of ingestion, caffeine intake mode or form, and habituation to caffeine could also have accounted for the varied effects on performance. Caffeine supplementation is more likely to help with endurance-type activities such as running and activities of long duration with intermittent activity such as soccer than more anaerobic, short-term bouts of intense exercise such as sprinting or lifting weights [ 91 ].

Some evidence suggests that caffeine is more likely to improve performance in people who are not habituated to it [ 85 ]. However, other evidence shows no habituation effect of caffeine consumption on performance [ 92 ]. Other adverse effects of caffeine include insomnia, restlessness, nausea, vomiting, tachycardia, and arrhythmia [ ].

Caffeine does not induce diuresis or increase sweat loss during exercise and therefore does not reduce fluid balance in the body that would adversely affect performance [ 13 , 90 , 98 ].

For healthy adults, the U. The American Academy of Pediatrics warns that caffeine-containing energy drinks in particular have no place in the diets of children or adolescents and are not suitable for use during routine physical activity [ ]. Pure powdered caffeine is available as a dietary supplement and is very potent.

Furthermore, combining caffeine with other stimulants could increase the potential for adverse effects [ 94 ]. At least two young men have died as a result of taking an unknown amount of pure powdered caffeine [ ].

Caffeine is easily and rapidly absorbed, even from the buccal membranes in the mouth, and is distributed throughout the body and brain. It reaches peak concentrations in the blood within 45 minutes of consumption and has a half-life of about 4—5 hours [ 83 ].

For a potential benefit to athletic performance, users should consume caffeine 15 to 60 minutes before exercise [ 13 , 85 ]. Consumption of caffeine with fluid during exercise of long duration might extend any performance improvements [ 85 ].

In a position statement, the AND, DoC, and ACSM state that caffeine supplementation reduces perceived fatigue and enables users to sustain exercise at the desired intensity longer [ 12 ]. The U. It adds that caffeine could reduce perceived exertion when exercise lasts longer. The Australian Institute of Sport supports the use of caffeine for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how caffeine should be used for best results [ 29 ].

The World Anti-Doping Agency does not prohibit or limit caffeine use [ ]. L-citrulline is a nonessential amino acid produced in the body, mainly from glutamine, and obtained from the diet. Watermelon is the best-known source; 1 cup diced seedless watermelon has about mg citrulline [ ].

The subsequent conversion of arginine to nitric oxide, a potent dilator of blood vessels, might be the mechanism by which citrulline could serve as an ergogenic aid. In fact, consumption of citrulline might be a more efficient way to raise blood arginine levels than consumption of arginine because more citrulline is absorbed from the gut than arginine.

Most studies have used citrulline malate, a combination of citrulline with malic acid a constituent in many fruits that is also produced endogenously , because malate, an intermediate in the Krebs cycle, might enhance energy production [ 30 ].

The research to support supplemental citrulline as an ergogenic aid is limited and conflicting at best. The few published studies have had heterogeneous designs and ranged in duration from 1 to 16 days. As an example, in one randomized controlled study with a crossover design, 41 healthy male weightlifters age 22—37 years consumed 8 g citrulline malate or a placebo 1 hour before completing barbell bench presses to exhaustion [ ].

Overall, participants could complete significantly more repetitions when taking the supplement and reported significantly less muscle soreness 1 and 2 days after the test.

Another study that randomized 17 young healthy men and women to take citrulline without malate either 3 g before testing or 9 g over 24 hours or a placebo found that participants using the citrulline did not perform as well as those taking the placebo on an incremental treadmill test to exhaustion [ ].

Although citrulline supplementation might increase plasma levels of nitric oxide metabolites, such a response has not been directly related to any improvement in athletic performance [ 30 ].

Studies have not adequately assessed the safety of citrulline, particularly when users take it in supplemental form for months at a time.

In the study of weight lifters described above, 6 of the 41 participants reported stomach discomfort after taking the supplement [ ].

The research to date does not provide strong support for taking citrulline or citrulline malate to enhance exercise or athletic performance [ 30 ]. Whether athletes in specific sports or activities might benefit from taking supplemental citrulline remains to be determined [ ].

Dietary supplements that contain citrulline provide either citrulline or citrulline malate. Citrulline malate is Sellers of some citrulline malate dietary supplements claim that they provide a higher percentage of citrulline with labels listing, for example, citrulline malate or tri-citrulline malate , but studies have not determined whether these supplements are superior to standard citrulline or citrulline malate supplements.

Creatine is one of the most thoroughly studied and widely used dietary supplements to enhance exercise and sports performance [ ]. Creatine is produced endogenously and obtained from the diet in small amounts.

It helps generate ATP and thereby supplies the muscles with energy, particularly for short-term events [ ]. A person weighing pounds has about g creatine and phosphocreatine in his or her body, almost all in the skeletal and cardiac muscles [ ].

However, it is only when users consume much greater amounts of creatine over time as a dietary supplement that it could have ergogenic effects. Metabolized creatine is converted into the waste product creatinine, which is eliminated from the body through the kidneys.

Studies in both laboratory and sports settings have found that short-term creatine supplementation for 5 to 7 days in both men and women often significantly increases strength e. In one example, a study randomized 14 healthy, resistance-trained men age 19—29 years to receive 25 g creatine monohydrate or a placebo for 6—7 days [ ].

Participants taking the supplement had significant improvements in peak power output during all five sets of jump squats and in repetitions during all five sets of bench presses on three occasions.

Compared with those taking the placebo, participants taking the creatine improved their performance in both meter sprints and six intermittent m sprints. Supplementation with creatine over weeks or months helps training adaptations to structured, increased workloads over time.

Individuals have varied responses to creatine supplementation, based on factors such as diet and the relative percentages of various muscle fiber types [ , ]. Vegetarians, for example, with their lower muscle creatine content, might have greater responses to supplementation than meat eaters.

Overall, creatine enhances performance during repeated short bursts of high-intensity, intermittent activity, such as sprinting and weight lifting, where energy for this predominantly anaerobic exercise comes mainly from the ATP-creatine phosphate energy system [ 38 , ].

Creatine supplementation seems to be of little value for endurance sports, such as distance running or swimming, that do not depend on the short-term ATP-creatine phosphate system to provide short-term energy, and it leads to weight gain that might impede performance in such sports [ , ].

Furthermore, in predominantly aerobic exercise lasting more than seconds, the body relies on oxidative phosphorylation as the primary energy source, a metabolic pathway that does not require creatine [ ]. Studies have found no consistent set of side effects from creatine use, except that it often leads to weight gain, because it increases water retention and possibly stimulates muscle protein synthesis [ , ].

Several studies have found that supplemental creatine monohydrate, when used for a strength-training program, can lead to a 1—2 kg increase in total body weight in a month [ 73 ].

Creatine is considered safe for short-term use by healthy adults [ 12 , , , ]. In addition, evidence shows that use of the product for several years is safe [ , ]. Anecdotal reactions to creatine use include nausea, diarrhea and related gastrointestinal distress, muscle cramps, and heat intolerance.

Creatine supplementation may reduce the range of motion of various parts of the body such as the shoulders, ankles, and lower legs and lead to muscle stiffness and resistance to stretching [ ]. Adequate hydration while taking creatine might minimize these uncommon risks [ ]. In a position statement, the AND, DoC, and ACSM advise that creatine enhances performance of cycles of high-intensity exercise followed by short recovery periods and improves training capacity [ 12 ].

In its position statement, the ISSN states that creatine monohydrate is the most effective nutritional supplement currently available for enhancing capacity for high-intensity exercise and lean body mass during exercise [ ].

The ISSN contends that athletes who supplement with creatine have a lower incidence of injuries and exercise-related side effects compared to those who do not take creatine [ ].

The Australian Institute of Sport supports the use of creatine for improving sports performance in suitable athletic competitions under the direction of an expert in sports medicine, but it notes that more research might be required to understand how the supplement should be used for best results [ 29 ].

In some studies, the loading dose is based on body weight e. Other, usually more expensive, forms of creatine e. Deer antler velvet consists of cartilage and epidermis from growing deer or elk antlers before ossification [ , ].

It is used as a general health aid in traditional Chinese medicine. Several growth factors have been detected in deer antler velvet, such as IGF-1, that could promote muscle tissue growth in a similar way to the quick growth of deer antlers. Three randomized controlled trials in a total of 95 young and middle-age men and 21 young females provide virtually no evidence that deer antler velvet supplements improve aerobic or anaerobic performance, muscular strength, or endurance [ , ].

The supplements provided no significant ergogenic effects compared with placebo. Studies have not adequately assessed the safety of deer antler velvet. The studies cited above found no side effects in participants taking deer-antler-velvet supplements. IGF-1 is available as a prescription medication, and its reported side effects include hypoglycemia, headache, edema, and joint pain [ ].

An evaluation of six deer-antler-velvet dietary supplements that were commercially available in found that five of them contained no deer IGF-1, and four were adulterated with human IGF-1 [ ].

Only one of the six supplements contained a low level of deer IGF The research to date does not support taking deer-antler-velvet supplements to enhance exercise or athletic performance.

The National Collegiate Athletic Association [ ] and the World Anti-Doping Agency [ ] ban the use of IGF-1 and its analogues in athletic competition. DHEA is a steroid hormone secreted by the adrenal cortex. The body can convert DHEA to the male hormone testosterone; testosterone's intermediary, androstenedione; and the female hormone estradiol [ ].

Testosterone is an anabolic steroid that promotes gains in muscle mass and strength when combined with resistance training [ ]. The minimal research on DHEA's use to enhance exercise and athletic performance provides no evidence of benefit [ ]. Buy 2 Items, Get a Free Gift. SHOP BY CATEGORY Shop All Products.

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