For these reasons, and due to an increase of published studies in areas related to optimal protein dosing, timing and composition, protein needs are being recommended within this position stand on a per meal basis. For example, Moore [ 31 ] found that muscle and albumin protein synthesis was optimized at approximately 20 g of egg protein at rest.

Witard et al. Furthermore, while results from these studies offer indications of what optimal absolute dosing amounts may be, Phillips [ ] concluded that a relative dose of 0.

Once a total daily target protein intake has been achieved, the frequency and pattern with which optimal doses are ingested may serve as a key determinant of overall changes in protein synthetic rates. Research indicates that rates of MPS rapidly rise to peak levels within 30 min of protein ingestion and are maintained for up to three hours before rapidly beginning to lower to basal rates of MPS even though amino acids are still elevated in the blood [ ].

Using an oral ingestion model of 48 g of whey protein in healthy young men, rates of myofibrillar protein synthesis increased three-fold within 45—90 min before slowly declining to basal rates of MPS all while plasma concentration of EAAs remained significantly elevated [ ].

While largely unexplored in a human model, these authors relied upon an animal model and were able to reinstate increases in MPS using the consumption of leucine and carbohydrate min after ingestion of the first meal. As such, it is suggested that individuals attempting to restrict caloric intake should consume three to four whole meals consisting of 20—40 g of protein per meal.

While this recommendation stems primarily from initial work that indicated protein doses of 20—40 g favorably promote increased rates of MPS [ 31 , , ], Kim and colleagues [ ] recently reported that a 70 g dose of protein promoted a more favorable net balance of protein when compared to a 40 g dose due to a stronger attenuation of rates of muscle protein breakdown.

For those attempting to increase their calories, we suggest consuming small snacks between meals consisting of both a complete protein and a carbohydrate source. This contention is supported by research from Paddon-Jones et al.

These researchers compared three cal mixed macronutrient meals to three cal meals combined with three cal amino acid-carbohydrate snacks between meals.

Additionally, using a protein distribution pattern of 20—25 g doses every three hours in response to a single bout of lower body resistance exercise appears to promote the greatest increase in MPS rates and phosphorylation of key intramuscular proteins linked to muscle hypertrophy [ ].

This simple addition could provide benefits for individuals looking to increase muscle mass and improve body composition in general while also striving to maintain or improve health and performance. The current RDA for protein is 0. While previous recommendations have suggested a daily intake of 1.

Daily and per dose needs are combinations of many factors including volume of exercise, age, body composition, total energy intake and training status of the athlete. Daily intakes of 1. Even higher amounts ~70 g appear to be necessary to promote attenuation of muscle protein breakdown.

Pacing or spreading these feeding episodes approximately three hours apart has been consistently reported to promote sustained, increased levels of MPS and performance benefits. There are 20 total amino acids, comprised of 9 EAAs and 11 non-essential amino acids NEAAs.

EAAs cannot be produced in the body and therefore must be consumed in the diet. Several methods exist to determine protein quality such as Chemical Score, Protein Efficiency Ratio, Biological Value, Protein Digestibility-Corrected Amino Acid Score PDCAAS and most recently, the Indicator Amino Acid Oxidation IAAO technique.

Ultimately, in vivo protein quality is typically defined as how effective a protein is at stimulating MPS and promoting muscle hypertrophy [ ]. Overall, research has shown that products containing animal and dairy-based proteins contain the highest percentage of EAAs and result in greater hypertrophy and protein synthesis following resistance training when compared to a vegetarian protein-matched control, which typically lacks one or more EAAs [ 86 , 93 , ].

Several studies, but not all, [ ] have indicated that EAAs alone stimulate protein synthesis in the same magnitude as a whole protein with the same EAA content [ 98 ]. For example, Borsheim et al. Moreover, Paddon-Jones and colleagues [ 96 ] found that a cal supplement containing 15 g of EAAs stimulated greater rates of protein synthesis than an cal meal with the same EAA content from a whole protein source.

While important, the impact of a larger meal on changes in circulation and the subsequent delivery of the relevant amino acids to the muscle might operate as important considerations when interpreting this data.

In contrast, Katsanos and colleagues [ ] had 15 elderly subjects consume either 15 g of whey protein or individual doses of the essential and nonessential amino acids that were identical to what is found in a g whey protein dose on separate occasions. Whey protein ingestion significantly increased leg phenylalanine balance, an index of muscle protein accrual, while EAA and NEAA ingestion exerted no significant impact on leg phenylalanine balance.

This study, and the results reported by others [ ] have led to the suggestion that an approximate 10 g dose of EAAs might serve as an optimal dose to maximally stimulate MPS and that intact protein feedings of appropriate amounts as opposed to free amino acids to elderly individuals may stimulate greater improvements in leg muscle protein accrual.

Based on this research, scientists have also attempted to determine which of the EAAs are primarily responsible for modulating protein balance. The three branched-chain amino acids BCAAs , leucine, isoleucine, and valine are unique among the EAAs for their roles in protein metabolism [ ], neural function [ , , ], and blood glucose and insulin regulation [ ].

Additionally, enzymes responsible for the degradation of BCAAs operate in a rate-limiting fashion and are found in low levels in splanchnic tissues [ ].

Thus, orally ingested BCAAs appear rapidly in the bloodstream and expose muscle to high concentrations ultimately making them key components of skeletal MPS [ ]. Furthermore, Wilson and colleagues [ ] have recently demonstrated, in an animal model, that leucine ingestion alone and with carbohydrate consumed between meals min post-consumption extends protein synthesis by increasing the energy status of the muscle fiber.

Multiple human studies have supported the contention that leucine drives protein synthesis [ , ]. Moreover, this response may occur in a dose-dependent fashion, plateauing at approximately two g at rest [ 31 , ], and increasing up to 3. However, it is important to realize that the duration of protein synthesis after resistance exercise appears to be limited by both the signal leucine concentrations , ATP status, as well as the availability of substrate i.

As such, increasing leucine concentration may stimulate increases in muscle protein, but a higher total dose of all EAAs as free form amino acids or intact protein sources seems to be most suited for sustaining the increased rates of MPS [ ].

It is well known that exercise improves net muscle protein balance and in the absence of protein feeding, this balance becomes more negative. When combined with protein feeding, net muscle protein balance after exercise becomes positive [ ]. Norton and Layman [ ] proposed that consumption of leucine, could turn a negative protein balance to a positive balance following an intense exercise bout by prolonging the MPS response to feeding.

In support, the ingestion of a protein or essential amino acid complex that contains sufficient amounts of leucine has been shown to shift protein balance to a net positive state after intense exercise training [ 46 , ].

Even though leucine has been demonstrated to independently stimulate protein synthesis, it is important to recognize that supplementation should not be with just leucine alone. For instance, Wilson et al. In summary, athletes should focus on consuming adequate leucine content in each of their meals through selection of high-quality protein sources [ ].

Protein sources containing higher levels of the EAAs are considered to be higher quality sources of protein. The body uses 20 amino acids to make proteins, seven of which are essential nine conditionally , requiring their ingestion to meet daily needs.

EAAs appear to be uniquely responsible for increasing MPS with doses ranging from 6 to 15 g all exerting stimulatory effects. In addition, doses of approximately one to three g of leucine per meal appear to be needed to stimulate protein translation machinery.

The BCAAs i. However, the extent to which these changes are aligned with changes in MPS remains to be fully explored. While greater doses of leucine have been shown to independently stimulate increases in protein synthesis, a balanced consumption of the EAAs promotes the greatest increases.

Milk proteins have undergone extensive research related to their potential roles in augmenting adaptations from exercise training [ 86 , 93 ].

For example, consuming milk following exercise has been demonstrated to accelerate recovery from muscle damaging exercise [ ], increase glycogen replenishment [ ], improve hydration status [ , ], and improve protein balance to favor synthesis [ 86 , 93 ], ultimately resulting in increased gains in both neuromuscular strength and skeletal muscle hypertrophy [ 93 ].

Moreover, milk protein contains the highest score on the PDCAAS rating system, and in general contains the greatest density of leucine [ ]. Milk can be fractionated into two protein classes, casein and whey. While both are high in quality, the two differ in the rate at which they digest as well as the impact they have on protein metabolism [ , , ].

Whey protein is water soluble, mixes easily, and is rapidly digested [ ]. In contrast, casein is water insoluble, coagulates in the gut and is digested more slowly than whey protein [ ]. Casein also has intrinsic properties such as opioid peptides, which effectively slow gastric motility [ ].

Original research investigating the effects of digestion rate was conducted by Boirie, Dangin and colleagues [ , , ]. These researchers gave a 30 g bolus of whey protein and a 43 g bolus of casein protein to subjects on separate occasions and measured amino acid levels for several hours after ingestion.

They reported that the whey protein condition displayed robust hyperaminoacidemia min after administration. However, by min, amino acid concentrations had returned to baseline. In contrast, the casein condition resulted in a slow increase in amino acid concentrations, which remained elevated above baseline after min.

Over the study duration, casein produced a greater whole body leucine balance than the whey protein condition, leading the researcher to suggest that prolonged, moderate hyperaminoacidemia is more effective at stimulating increases in whole body protein anabolism than a robust, short lasting hyperaminoacidemia.

While this research appears to support the efficacy of slower digesting proteins, subsequent work has questioned its validity in athletes.

The first major criticism is that Boire and colleagues investigated whole body non-muscle and muscle protein balance instead of skeletal myofibrillar MPS. These findings suggest that changes in whole body protein turnover may poorly reflect the level of skeletal muscle protein metabolism that may be taking place.

Trommelen and investigators [ ] examined 24 young men ingesting 30 g of casein protein with or without completion of a single bout of resistance exercise, and concluded that rates of MPS were increased, but whole-body protein synthesis rates were not impacted.

More recently, Tang and colleagues [ 86 ] investigated the effects of administering 22 g of hydrolyzed whey isolate and micellar casein 10 g of EAAs at both rest and following a single bout of resistance training in young males.

Moreover, these researchers reported that whey protein ingestion stimulated greater MPS at both rest and following exercise when compared to casein. In comparison to the control group, both whey and casein significantly increased leucine balance, but no differences were found between the two protein sources for amino acid uptake and muscle protein balance.

Additional research has also demonstrated that 10 weeks of whey protein supplementation in trained bodybuilders resulted in greater gains in lean mass 5. These findings suggest that the faster-digesting whey proteins may be more beneficial for skeletal muscle adaptations than the slower digesting casein.

Skeletal muscle glycogen stores are a critical element to both prolonged and high-intensity exercise. In skeletal muscle, glycogen synthase activity is considered one of the key regulatory factors for glycogen synthesis. Research has demonstrated that the addition of protein in the form of milk and whey protein isolate 0.

Further, the addition of protein facilitates repair and recovery of the exercised muscle [ 12 ]. These effects are thought to be related to a greater insulin response following the exercise bout. Intriguingly, it has also been demonstrated that whey protein enhances glycogen synthesis in the liver and skeletal muscle more than casein in an insulin-independent fashion that appears to be due to its capacity to upregulate glycogen synthase activity [ ].

Therefore, the addition of milk protein to a post-workout meal may augment recovery, improve protein balance, and speed glycogen replenishment. While athletes tend to view whey as the ideal protein for skeletal muscle repair and function it also has several health benefits.

In particular, whey protein contains an array of biologically active peptides whose amino acids sequences give them specific signaling effects when liberated in the gut.

Furthermore, whey protein appears to play a role in enhancing lymphatic and immune system responses [ ]. In addition, α-lactalbumin contains an ample supply of tryptophan which increases cognitive performance under stress [ ], improves the quality of sleep [ , ], and may also speed wound healing [ ], properties which could be vital for recovery from combat and contact sporting events.

In addition, lactoferrin is also found in both milk and in whey protein, and has been demonstrated to have antibacterial, antiviral, and antioxidant properties [ ].

Moreover, there is some evidence that whey protein can bind iron and therefore increase its absorption and retention [ ]. Egg protein is often thought of as an ideal protein because its amino acid profile has been used as the standard for comparing other dietary proteins [ ].

Due to their excellent digestibility and amino acid content, eggs are an excellent source of protein for athletes. While the consumption of eggs has been criticized due to their cholesterol content, a growing body of evidence demonstrates the lack of a relationship between egg consumption and coronary heart disease, making egg-based products more appealing [ ].

One large egg has 75 kcal and 6 g of protein, but only 1. Research using eggs as the protein source for athletic performance and body composition is lacking, perhaps due to less funding opportunities relative to funding for dairy.

Egg protein may be particularly important for athletes, as this protein source has been demonstrated to significantly increase protein synthesis of both skeletal muscle and plasma proteins after resistance exercise at both 20 and 40 g doses.

Leucine oxidation rates were found to increase following the 40 g dose, suggesting that this amount exceeds an optimal dose [ 31 ]. In addition to providing a cost effective, high-quality source of protein rich in leucine 0. Functional foods are defined as foods that, by the presence of physiologically active components, provide a health benefit beyond basic nutrition [ ].

According to the Academy of Nutrition and Dietetics, functional foods should be consumed as part of a varied diet on a regular basis, at effective levels [ ]. Thus, it is essential that athletes select foods that meet protein requirements and also optimize health and prevent decrements in immune function following intense training.

Eggs are also rich in choline, a nutrient which may have positive effects on cognitive function [ ]. Moreover, eggs provide an excellent source of the carotenoid-based antioxidants lutein and zeaxanthin [ ]. Also, eggs can be prepared with most meal choices, whether at breakfast, lunch, or dinner.

Such positive properties increase the probability of the athletes adhering to a diet rich in egg protein. Meat proteins are a major staple in the American diet and, depending on the cut of meat, contain varying amounts of fat and cholesterol.

Meat proteins are well known to be rich sources of the EAAs [ ]. Beef is a common source of dietary protein and is considered to be of high biological value because it contains the full balance of EAAs in a fraction similar to that found in human skeletal muscle [ ].

A standard serving of Moreover, this 30 g dose of beef protein has been shown to stimulate protein synthesis in both young and elderly subjects [ ]. In addition to its rich content of amino acids, beef and other flesh proteins can serve as important sources of micronutrients such as iron, selenium, vitamins A, B12 and folic acid.

This is a particularly important consideration for pregnant and breastfeeding women. Ultimately, as an essential part of a mixed diet, meat helps to ensure adequate distribution of essential micronutrients and amino acids to the body.

Research has shown that significant differences in skeletal muscle mass and body composition between older men who resistance train and either consume meat-based or lactoovovegetarian diet [ ].

Over a week period, whole-body density, fat-free mass, and whole-body muscle mass as measured by urinary creatinine excretion increased in the meat-sourced diet group but decreased in the lactoovovegetarian diet group. These results indicate that not only do meat-based diets increase fat-free mass, but also they may specifically increase muscle mass, thus supporting the many benefits of meat-based diets.

A diet high in meat protein in older adults may provide an important resource in reducing the risk of sarcopenia. Positive results have also been seen in elite athletes that consume meat-based proteins, as opposed to vegetarian diets [ ]. For example, carnitine is a molecule that transports long-chain fatty acids into mitochondria for oxidation and is found in high amounts in meat.

While evidence is lacking to support an increase in fat oxidation with increased carnitine availability, carnitine has been linked to the sparing of muscle glycogen, and decreases in exercise-induced muscle damage [ ].

Certainly, more research is needed to support these assertions. Creatine is a naturally occurring compound found mainly in muscle. Vegetarians have lower total body creatine stores than omnivores, which demonstrates that regular meat eating has a significant effect on human creatine status [ ].

Moreover, creatine supplementation studies with vegetarians indicate that increased creatine uptake levels do exist in people who practice various forms of vegetarianism [ ]. Sharp and investigators [ ] published the only study known to compare different supplemental powdered forms of animal proteins on adaptations to resistance training such as increases in strength and improvements in body composition.

Forty-one men and women performed a standardized resistance-training program over eight weeks and consumed a daily 46 g dose of either hydrolyzed chicken protein, beef protein isolate, or whey protein concentrate in comparison to a control group. All groups experienced similar increases in upper and lower-body strength, but all protein-supplemented groups reported significant increases in lean mass and decreases in fat mass.

Meat-based diets have been shown to include additional overall health benefits. Some studies have found that meat, as a protein source, is associated with higher serum levels of IGF-1 [ ], which in turn is related to increased bone mineralization and fewer fractures [ ]. A highly debated topic in nutrition and epidemiology is whether vegetarian diets are a healthier choice than omnivorous diets.

One key difference is the fact that vegetarian diets often lack equivalent amounts of protein when compared to omnivorous diets [ ]. However, with proper supplementation and careful nutritional choices, it is possible to have complete proteins in a vegetarian diet.

Generally by consuming high-quality, animal-based products meat, milk, eggs, and cheese an individual will achieve optimal growth as compared to ingesting only plant proteins [ ]. Research has shown that soy is considered a lower quality complete protein.

Hartman et al. They found that the participants that consumed the milk protein increased lean mass and decreased fat mass more than the control and soy groups. Moreover, the soy group was not significantly different from the control group. Similarly, a study by Tang and colleagues [ 86 ] directly compared the abilities of hydrolyzed whey isolate, soy isolate, and micellar casein to stimulate rates of MPS both at rest and in response to a single bout of lower body resistance training.

These authors reported that the ability of soy to stimulate MPS was greater than casein, but less than whey, at rest and in response to an acute resistance exercise stimulus.

While soy is considered a complete protein, it contains lower amounts of BCAAs than bovine milk [ ]. Additionally, research has found that dietary soy phytoestrogens inhibit mTOR expression in skeletal muscle through activation of AMPK [ ].

Thus, not only does soy contain lower amounts of the EAAs and leucine, but soy protein may also be responsible for inhibiting growth factors and protein synthesis via its negative regulation of mTOR. When considering the multitude of plant sources of protein, soy overwhelmingly has the most research.

Limited evidence using wheat protein in older men has suggested that wheat protein stimulates significantly lower levels of MPS when compared to an identical dose 35 g of casein protein, but when this dose is increased nearly two fold 60 g this protein source is able to significantly increase rates of myofibrillar protein synthesis [ ].

As mentioned earlier, a study by Joy and colleagues [ 89 ] in which participants participated in resistance training program for eight weeks while taking identical, high doses of either rice or whey protein, demonstrated that rice protein stimulated similar increases in body composition adaptations to whey protein.

The majority of available science has explored the efficacy of ingesting single protein sources, but evidence continues to mount that combining protein sources may afford additional benefits [ ]. For example, a week resistance training study by Kerksick and colleagues [ 22 ] demonstrated that a combination of whey 40 g and casein 8 g yielded the greatest increase in fat-free mass determined by DEXA when compared to both a combination of 40 g of whey, 5 g of glutamine, and 3 g of BCAAs and a placebo consisting of 48 g of a maltodextrin carbohydrate.

Later, Kerksick et al. Similarly, Hartman and investigators [ 93 ] had 56 healthy young men train for 12 weeks while either ingesting isocaloric and isonitrogenous doses of fat-free milk a blend of whey and casein , soy protein or a carbohydrate placebo and concluded that fat-free milk stimulated the greatest increases in Type I and II muscle fiber area as well as fat-free mass; however, strength outcomes were not affected.

Moreover, Wilkinson and colleagues [ 94 ] demonstrated that ingestion of fat-free milk vs. soy or carbohydrate led to a greater area under the curve for net balance of protein and that the fractional synthesis rate of muscle protein was greatest after milk ingestion.

In , Reidy et al. However, when the entire four-hour measurement period was considered, no difference in MPS rates were found. A follow-up publication from the same clinical trial also reported that ingestion of the protein blend resulted in a positive and prolonged amino acid balance when compared to ingestion of whey protein alone, while post-exercise rates of myofibrillar protein synthesis were similar between the two conditions [ ].

Reidy et al. No differences were found between whey and the whey and soy blend. Some valid criteria exist to compare protein sources and provide an objective method of how to include them in a diet. As previously mentioned, common means of assessing protein quality include Biological Value, Protein Efficiency Ratio, PDCAAS and IAAO.

The derivation of each technique is different with all having distinct advantages and disadvantages. For nearly all populations, ideal methods should be linked to the capacity of the protein to positively affect protein balance in the short term, and facilitate increases and decreases in lean and fat-mass, respectively, over the long term.

To this point, dairy, egg, meat, and plant-based proteins have been discussed. As mentioned previously, initial research by Boirie and Dangin has highlighted the impact of protein digestion rate on net protein balance with the two milk proteins: whey and casein [ , , ].

Subsequent follow-up work has used this premise as a reference point for the digestion rates of other protein sources. Using the criteria of leucine content, Norton and Wilson et al. Wheat and soy did not stimulate MPS above fasted levels, whereas egg and whey proteins significantly increased MPS rates, with MPS for whey protein being greater than egg protein.

MPS responses were closely related to changes in plasma leucine and phosphorylation of 4E—BP1 and S6 K protein signaling molecules. More importantly, following 2- and weeks of ingestion, it was demonstrated that the leucine content of the meals increased muscle mass and was inversely correlated with body fat.

Tang et al. These findings lead us to conclude that athletes should seek protein sources that are both fast-digesting and high in leucine content to maximally stimulate rates of MPS at rest and following training. Moreover, in consideration of the various additional attributes that high-quality protein sources deliver, it may be advantageous to consume a combination of higher quality protein sources dairy, egg, and meat sources.

Multiple protein sources are available for an athlete to consider, and each has their own advantages and disadvantages. Protein sources are commonly evaluated based upon the content of amino acids, particularly the EAAs, they provide. Blends of protein sources might afford a favorable combination of key nutrients such as leucine, EAAs, bioactive peptides, and antioxidants, but more research is needed to determine their ideal composition.

Nutrient density is defined as the amount of a particular nutrient carbohydrate, protein, fat, etc. per unit of energy in a given food. In many situations, the commercial preparation method of foods can affect the actual nutrient density of the resulting food. When producing milk protein supplements, special preparations must be made to separate the protein sources from the lactose and fat calories in milk.

For example, the addition of acid to milk causes the casein to coagulate or collect at the bottom, while the whey is left on the top [ ]. These proteins are then filtered to increase their purity.

Filtration methods differ, and there are both benefits and disadvantages to each. Ion exchange exposes a given protein source, such as whey, to hydrochloric acid and sodium hydroxide, thereby producing an electric charge on the proteins that can be used to separate them from lactose and fat [ ].

The advantage of this method is that it is relatively cheap and produces the highest protein concentration [ ]. The disadvantage is that ion exchange filtration typically denatures some of the valuable immune-boosting, anti-carcinogenic peptides found in whey [ ].

Cross-flow microfiltration, and ultra-micro filtration are based on the premise that the molecular weight of whey protein is greater than lactose, and use 1 and 0.

As a result, whey protein is trapped in the membranes but the lactose and other components pass through. The advantage is that these processes do not denature valuable proteins and peptides found in whey, so the protein itself is deemed to be of higher quality [ ].

The main disadvantage is that this filtration process is typically costlier than the ion exchange method. When consumed whole, proteins are digested through a series of steps beginning with homogenization by chewing, followed by partial digestion by pepsin in the stomach [ ].

Following this, a combination of peptides, proteins, and negligible amounts of single amino acids are released into the small intestine and from there are either partially hydrolyzed into oligopeptides, 2—8 amino acids in length or are fully hydrolyzed into individual amino acids [ ].

Absorption of individual amino acids and various small peptides di, tri, and tetra into the blood occurs inside the small intestine through separate transport mechanisms [ ].

Oftentimes, products contain proteins that have been pre-exposed to specific digestive enzymes causing hydrolysis of the proteins into di, tri, and tetrapeptides. A plethora of studies have investigated the effects of the degree of protein fractionation or degree of hydrolysis on the absorption of amino acids and the subsequent hormonal response [ , , , , , ].

Further, the rate of absorption may lead to a more favorable anabolic hormonal environment [ , , ]. Calbet et al.

Each of the nitrogen containing solutions contained 15 g of glucose and 30 g of protein. Results indicated that peptide hydrolysates produced a faster increase in venous plasma amino acids compared to milk proteins.

Further, the peptide hydrolysates produced peak plasma insulin levels that were two- and four-times greater than that evoked by the milk and glucose solutions, respectively, with a correlation of 0.

In a more appropriate comparison, Morifuji et al. However, Calbet et al. The hydrolyzed casein, however, did result in a greater amino acid response than the nonhydrolyzed casein. Finally, both hydrolyzed groups resulted in greater gastric secretions, as well as greater plasma increases, in glucose-dependent insulinotropic polypeptides [ ].

Buckley and colleagues [ ] found that a ~ 30 g dose of a hydrolyzed whey protein isolate resulted in a more rapid recovery of muscle force-generating capacity following eccentric exercise, compared with a flavored water placebo or a non-hydrolyzed form of the same whey protein isolate.

In agreement with these findings, Cooke et al. Three and seven days after completing the damaging exercise bout, maximal strength levels were higher in the hydrolyzed whey protein group compared to carbohydrate supplementation.

Additionally, blood concentrations of muscle damage markers tended to be lower when four ~g doses of a hydrolyzed whey protein isolate were ingested for two weeks following the damaging bout. Beyond influencing strength recovery after damaging exercise, other benefits of hydrolyzed proteins have been suggested.

For example, Morifuji et al. Furthermore, Lockwood et al. Results indicated that strength and lean body mass LBM increased equally in all groups. However, fat mass decreased only in the hydrolyzed whey protein group.

While more work needs to be completed to fully determine the potential impact of hydrolyzed proteins on strength and body composition changes, this initial study suggests that hydrolyzed whey may be efficacious for decreasing body fat.

Finally, Saunders et al. The authors reported that co-ingestion of a carbohydrate and protein hydrolysate improved time-trial performance late in the exercise protocol and significantly reduced soreness and markers of muscle damage.

Two excellent reviews on the topic of hydrolyzed proteins and their impact on performance and recovery have been published by Van Loon et al. The prevalence of digestive enzymes in sports nutrition products has increased during recent years with many products now containing a combination of proteases and lipases, with the addition of carbohydrates in plant proteins.

Proteases can hydrolyze proteins into various peptide configurations and potentially single amino acids. It appears that digestive enzyme capabilities and production decrease with age [ ], thus increasing the difficulty with which the body can break down and digest large meals.

Digestive enzymes could potentially work to promote optimal digestion by allowing up-regulation of various metabolic enzymes that may be needed to allow for efficient bodily operation. Further, digestive enzymes have been shown to minimize quality differences between varying protein sources [ ].

Individuals looking to increase plasma peak amino acid concentrations may benefit from hydrolyzed protein sources or protein supplemented with digestive enzymes. However, more work is needed before definitive conclusions can be drawn regarding the efficacy of digestive enzymes.

Despite a plethora of studies demonstrating safety, much concern still exists surrounding the clinical implications of consuming increased amounts of protein, particularly on renal and hepatic health.

The majority of these concerns stem from renal failure patients and educational dogma that has not been rewritten as evidence mounts to the contrary. Certainly, it is clear that people in renal failure benefit from protein-restricted diets [ ], but extending this pathophysiology to otherwise healthy exercise-trained individuals who are not clinically compromised is inappropriate.

Published reviews on this topic consistently report that an increased intake of protein by competitive athletes and active individuals provides no indication of hepato-renal harm or damage [ , ]. This is supported by a recent commentary [ ] which referenced recent reports from the World Health Organization [ ] where they indicated a lack of evidence linking a high protein diet to renal disease.

Likewise, the panel charged with establishing reference nutrient values for Australia and New Zealand also stated there was no published evidence that elevated intakes of protein exerted any negative impact on kidney function in athletes or in general [ ].

Recently, Antonio and colleagues published a series of original investigations that prescribed extremely high amounts of protein ~3. The first study in had resistance-trained individuals consume an extremely high protein diet 4.

A follow-up investigation [ ] required participants to ingest up to 3. Their next study employed a crossover study design in twelve healthy resistance-trained men in which each participant was tested before and after for body composition as well as blood-markers of health and performance [ ].

In one eight-week block, participants followed their normal habitual diet 2. No changes in body composition were reported, and importantly, no clinical side effects were observed throughout the study.

Finally, the same group of authors published a one-year crossover study [ ] in fourteen healthy resistance-trained men. This investigation showed that the chronic consumption of a high protein diet i.

Furthermore, there were no alterations in clinical markers of metabolism and blood lipids. Multiple review articles indicate that no controlled scientific evidence exists indicating that increased intakes of protein pose any health risks in healthy, exercising individuals.

A series of controlled investigations spanning up to one year in duration utilizing protein intakes of up to 2. In alignment with our previous position stand, it is the position of the International Society of Sports Nutrition that the majority of exercising individuals should consume at minimum approximately 1.

The amount is dependent upon the mode and intensity of the exercise, the quality of the protein ingested, as well as the energy and carbohydrate status of the individual.

Concerns that protein intake within this range is unhealthy are unfounded in healthy, exercising individuals. An attempt should be made to consume whole foods that contain high-quality e. The timing of protein intake in the period encompassing the exercise session may offer several benefits including improved recovery and greater gains in lean body mass.

In addition, consuming protein pre-sleep has been shown to increase overnight MPS and next-morning metabolism acutely along with improvements in muscle size and strength over 12 weeks of resistance training.

Intact protein supplements, EAAs and leucine have been shown to be beneficial for the exercising individual by increasing the rates of MPS, decreasing muscle protein degradation, and possibly aiding in recovery from exercise. In summary, increasing protein intake using whole foods as well as high-quality supplemental protein sources can improve the adaptive response to training.

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The effects of supplementation with creatine and protein on muscle strength following a traditional resistance training program in middle-aged and older men. J Nutr Health Aging. Burke DG, Chilibeck PD, Davidson KS, Candow DG, Farthing J, Smith-Palmer T. At present, creatine monohydrate is the most extensively studied and clinically effective form of creatine for use in nutritional supplements in terms of muscle uptake and ability to increase high-intensity exercise capacity.

The addition of carbohydrate or carbohydrate and protein to a creatine supplement appears to increase muscular uptake of creatine, although the effect on performance measures may not be greater than using creatine monohydrate alone. Initially, ingesting smaller amounts of creatine monohydrate e.

Clinical populations have been supplemented with high levels of creatine monohydrate 0. Further research is warranted to examine the potential medical benefits of creatine monohydrate and precursors like guanidinoacetic acid on sport, health and medicine.

Research examining the impact of the essential amino acids on stimulating muscle protein synthesis is an extremely popular area. Theoretically, this may enhance increases in fat-free mass, but to date limited evidence exists to demonstrate that supplementation with non-intact sources of EAAs e.

Moreover, other research has indicated that changes in muscle protein synthesis may not correlate with phenotypic adaptations to exercise training [ ]. An abundance of evidence is available, however, to indicate that ingestion of high-quality protein sources can heighten adaptations to resistance training [ ].

While various methods of protein quality assessment exist, most of these approaches center upon the amount of EAAs that are found within the protein source, and in nearly all situations, the highest quality protein sources are those containing the highest amounts of EAAs.

To this point, a number of published studies are available that state the EAAs operate as a prerequisite to stimulate peak rates of muscle protein synthesis [ , , , ]. To better understand the impact of ingesting free-form amino acids versus an intact protein source, Katsanos et al.

Protein accrual was greater when the amino acid dose was provided in an intact source. While the EAAs are comprised of nine separate amino acids, some individual EAAs have received considerable attention for their potential role in impacting protein translation and muscle protein synthesis.

In this respect, the branched-chain amino acids have been highlighted for their predominant role in stimulating muscle protein synthesis [ , ]. Interestingly, Moberg and investigators [ ] had trained volunteers complete a standardized bout of resistance training in conjunction with ingestion of placebo, leucine, BCAA or EAA while measuring changes in post-exercise activation of p70s6k.

They concluded that EAA ingestion led to a nine-fold greater increase in p70s6k activation and that these results were primarily attributable to the BCAAs. Finally, a study by Jackman et al.

While significant, this magnitude of change was notably less than the post-exercise MPS responses seen when doses of whey protein that delivered similar amounts of the BCAAs were consumed [ 88 , ]. These outcomes led the authors to conclude that the full complement of EAAs was advised to maximally stimulate increases in MPS.

Of all the interest captured by the BCAAs, leucine is accepted to be the primary driver of acute changes in protein translation. In this respect, Dreyer et al. In this respect, Jager et al.

A growing body of literature is available that suggests higher amounts of protein are needed by exercising individuals to optimize exercise training adaptations [ 11 , 83 , , ].

Collectively, these sources indicate that people undergoing intense training with the primary intention to promote accretion of fat-free mass should consume between 1. Tang and colleagues [ 95 ] conducted a classic study that examined the ability of three different sources of protein hydrolyzed whey isolate, micellar casein and soy isolate to stimulate acute changes in muscle protein synthesis both at rest and after a single bout of resistance exercise.

These authors concluded that all three protein sources significantly increased muscle protein synthesis rates both at rest and in response to resistance exercise. When this response is extrapolated over the course of several weeks, multiple studies have reported on the ability of different forms of protein to significantly increase fat-free mass while resistance training [ 70 , , , , , , ].

Cermak et al. Data from 22 separate published studies that included research participants were included in the analysis. These authors concluded that protein supplementation demonstrated a positive effect of fat-free mass and lower-body strength in both younger and older participants.

Similarly, Morton and investigators [ 83 ] published results from a meta-analysis that also included a meta-regression approach involving data from 49 studies and participants. They concluded that the ability of protein to positively impact fat-free mass accretion increases up to approximately 1.

Although more research is necessary in this area, evidence clearly indicates that protein needs of individuals engaged in intense training are elevated and consequently those athletes who achieve higher intakes of protein while training promote greater changes in fat-free mass. Beyond the impact of protein to foster greater training-induced adaptations such as increases in strength and muscle mass, several studies have examined the ability of different types of protein to stimulate changes in fat-free mass [ , , , , ] while several studies and reviews have critically explored the role protein may play in achieving weight loss in athletes [ , ] as well as during periods of caloric restriction [ , ].

It is the position stand of ISSN that exercising individuals need approximately 1. ATP is the primary intracellular energy source and in addition, has extensive extracellular functions including the increase in skeletal muscle calcium permeability and vasodilation.

While intravenous administration of ATP is bioavailable [ ], several studies have shown that oral ATP is not systematically bioavailable [ ]. However, chronic supplementation with ATP increases the capacity to synthesize ATP within the erythrocytes without increasing resting concentrations in the plasma, thereby minimizing exercise-induced drops in ATP levels [ ].

Oral ATP supplementation has demonstrated initial ergogenic properties, after a single dose, improving total weight lifted and total number of repetitions [ ]. ATP may increase blood flow to the exercising muscle [ ] and may reduce fatigue and increase peak power output during later bouts of repeated bouts exercise [ ].

ATP may also support greater recovery and lean mass maintenance under high volume training [ ], however, this has only been reported in one previous study. In addition, ATP supplementation in clinical populations has been shown to improve strength, reduce pain after knee surgery, and reduce the length of the hospital stay [ ].

However, given the limited number of human studies of ATP on increasing exercise-induced gains in muscle mass, more chronic human training studies are warranted. Leucine, in particular, is recognized as a keystone of sorts that when provided in the correct amounts 3—6 g activates the mTORC1 complex resulting in favorable initiation of translation [ ].

To highlight this impact for leucine, varying doses of whey protein and leucine levels were provided to exercising men at rest and in response to an acute bout of lower-body resistance exercise to examine the muscle protein synthetic response. Interestingly, when a low dose of whey protein 6.

While the g dose of whey protein did favorably sustain the increases in muscle protein synthesis, the added leucine highlights an important role for leucine in stimulating muscle protein synthesis in response to resistance exercise [ ].

For these reasons, it has been speculated that the leucine content of whey protein and other high-quality protein sources have been suggested to be primary reasons for their ability to stimulate favorable adaptations to resistance training [ , ].

Theoretically, BCAA supplementation during intense training may help minimize protein degradation and thereby lead to greater gains in or limit losses of fat-free mass, but only limited evidence exists to support this hypothesis. Bigard and associates [ ] reported that BCAA supplementation appeared to minimize loss of muscle mass in subjects training at altitude for 6 weeks.

Alternatively, Spillane and colleagues [ ] reported that 8 weeks of resistance training while supplementing with either 9 g of BCAAs or placebo did not impact body composition or muscle performance. Most recently, Jackman et al. As mixed outcomes cloud the ability to make clear determinations, studies strongly suggest a mechanistic role for BCAAs and in particular leucine, yet translational data fails to consistently support the need for BCAA supplementation.

Alternatively, multiple studies do support BCAAs ability to mitigate recovery from damaging exercise while their ability to favorably impact resistance training adaptations needs further research.

This will be discussed in a later section. Phosphatidic acid PA is a diacyl-glycerophospholipid that is enriched in eukaryotic cell membranes and it can act as a signalling lipid [ ]. Interestingly, PA has been repeatedly shown to activate the mammalian target of rapamycin mTOR signalling in muscle; an effect which ultimately leads to increases in muscle protein synthesis.

For instance, Fang et al. Hornberger et al. Hoffman et al. Joy et al. A third study confirmed the beneficial effects of PA on exercise-induced gains in lean body mass [ ].

The currently established dose of PA is mg per day and another study investigating lower doses, and mg per day, failed to show significant benefits on lean body mass [ ].

Hence, preliminary human research suggests that PA supplementation can increase anabolic signalling in skeletal muscle and enhance gains in muscle mass with resistance training.

Given that PA supplementation studies are in their infancy relative to other muscle-building supplements e. Agmatine, the decarboxylation product of the amino acid L-arginine, has shown different biological effects in different in vitro and animal models [ ] indicating potential benefits in an athletic population.

Agmatine is thought to improve insulin release and glucose uptake, assist in the secretion of luteinizing hormone, influence the nitric oxide signalling pathway, offer protection from oxidative stress, and is potentially involved in neurotransmission [ ].

It is mostly found in fermented foods [ ], with higher levels found in alcoholic beverages. Currently, nearly all research involving agmatine is commonly from animal research models and no human studies have been conducted to examine its impact on blood flow or impacting resistance training adaptations such as strength and body composition.

There does not appear to be any scientific evidence that Agmatine supports increases in lean body mass or muscular performance.

α-ketoglutarate α-KG is an intermediate in the Krebs cycle that is involved in aerobic energy metabolism and may function to stimulate nitric oxide production. There is some clinical evidence that α-KG may serve as an anticatabolic nutrient after surgery [ , ].

However, it is unclear whether α-KG supplementation during training may affect training adaptations. Very little research has been conducted on just alpha-ketoglutarate in humans to examine exercise outcomes. For example, Little and colleagues [ ] supplemented with creatine, a combination of creatine, α-KG, taurine, BCAA and medium-chain triglycerides, or a placebo.

The combination of nutrients increased the maximal number of bench press repetitions completed and Wingate peak power while no changes were reported in the placebo group. Campbell and investigators [ ] supplemented 35 healthy trained men with 2 g of arginine and 2 g of α-KG or placebo in a double-blind manner while resistance training for 8 weeks.

Finally, Willoughby and colleagues [ ] examined the results of arginine α-KG supplementation in relation to increasing nitric oxide production vasodilation during resistance exercise , hemodynamics, brachial artery flow, circulating levels of l-arginine, and asymmetric dimethyl arginine in active males.

This study found that although plasma L-arginine increased, there was no significant impact of supplementation on nitric oxide production after a bout of resistance exercise.

Due to the lack of research on α-KG examining its impact on exercise training adaptations, its use cannot be recommended at this time. Arginine is commonly classified as a conditionally essential amino acid and has been linked to nitric oxide production and increases in blood flow that are purported to then stimulate enhanced nutrient and hormone delivery and favorably impact resistance training adaptations [ ].

To date, few studies have examined the independent impact of arginine on the ability to enhance fat-free mass increases while resistance training. Tang and colleagues [ ] used an acute model to examine the ability of an oral g dose of arginine to stimulate changes in muscle protein synthesis.

These authors reported that arginine administration failed to impact muscle protein synthesis or femoral artery blood flow. Growth hormone levels did rise in response to arginine ingestion, which contrasts with the findings of Forbes et al.

Regardless, the Tang study [ ] and others [ , ] failed to link the increase in growth hormone to changes in rates of muscle protein synthesis. Notably, other studies have also failed to show a change in blood flow after arginine ingestion, one of its key purported benefits [ , ].

Campbell and colleagues published outcomes from an 8 week resistance training study that supplemented healthy men in a double-blind fashion with either a placebo or 2 g of arginine and 2 g of α-ketoglutarate.

No changes in fat mass or fat-free mass were reported in this study. Therefore, due to the limited data of arginine supplementation on stimulating further increases of exercise in muscle mass, its use for is not recommended at this time. Boron is a trace mineral whose physiological role is not clearly understood.

A number of proposed functions have been touted for boron: vitamin D metabolism, macromineral metabolism, immune support, increase testosterone levels and promote anabolism [ ]. Due to a lack of scientific evidence surrounding boron, no official Daily Reference Intake DRI is established.

Several studies have evaluated the effects of boron supplementation during training on strength and body composition alterations.

However, these studies conducted on male bodybuilders indicate that boron supplementation 2. Further, two investigations [ , ] examined the impact of boron supplementation on bone mineral density in athletic and sedentary populations. In both investigations, boron supplementation did not significantly influence bone mineral density.

Therefore, due to the limited findings on boron supplementation, its use is not recommended, and more research is warranted to determine its physiological impact. Chromium is a trace mineral that is actively involved in macronutrient metabolism.

Clinical studies have suggested that chromium potentiates the effects of insulin, particularly in diabetic populations. Due to its close interaction with insulin, chromium supplementation has been theorized to impact anabolism and exercise training adaptations.

Initial research was promising with chromium supplementation being associated with increases in muscle and strength, particularly in women [ , , ]. Most recently, chromium supplementation was investigated for its ability to impact glycogen synthesis after high-intensity exercise and was found to exert no impact over recovery of glycogen [ ].

In summary, chromium supplementation appears to exert very little potential for its ability to stimulate or support improvements in fat-free mass. Animal studies indicate that adding CLA to dietary feed decreases body fat, increases muscle and bone mass, has anti-cancer properties, enhances immunity, and inhibits progression of heart disease [ , , ].

Although animal studies are impressive [ , , ], human studies, at best, suggest a modest ability, independent of exercise or diet changes, of CLA to stimulate fat loss [ , , , ].

Moreover, very little research has been conducted on CLA to better understand if any scenario exists where its use may be justified. Initial work by Pinkoski et al. Two studies are available that supplemented exercising younger [ ] and older individuals [ ] with a combination of CLA and creatine and reported significant improvements in strength and body composition, but these results are thought to be the result of creatine.

Currently, it seems there is little evidence that CLA supplementation during training can affect lean tissue accretion and has limited efficacy [ ]. Also known as aspartate, aspartic acid is a non-essential amino acid.

Two isomers exist within aspartic acid: L-Aspartic acid and D-Aspartic acid. D-Aspartic acid is thought to help boost athletic performance and function as a testosterone booster.

It is also used to conserve muscle mass. While limited research is available in humans examining D-aspartic, Willoughby and Leutholtz [ ] published a study to determine the impact of D-aspartic acid in relation to testosterone levels and performance in resistance-trained males.

The results showed D-aspartic acid did not impact testosterone levels nor did it improve any aspect of performance. In agreement, Melville and colleagues [ ] had participants supplement with either three or 6 g of D-aspartic acid and concluded that neither dose of D-aspartic acid stimulated any changes in testosterone and other anabolic hormones.

Later, Melville et al. Based on the currently available literature, D-aspartic acid is not recommended to improve muscle health. Ecdysterones also known as ectysterone, 20 β-Hydroxyecdysterone, turkesterone, ponasterone, ecdysone, or ecdystene are naturally derived phytoecdysteroids i.

They are typically extracted from the herbs Leuza rhaptonticum sp. They can also be found in high concentrations in the herb Suma also known as Brazilian Ginseng or Pfaffia.

Initial interest was generated for ecdysterones due to reports of research from Russia and Czechoslovakia that indicated a potential physiological benefit in insects and animals [ , , , ].

A review by Bucci on various herbals and exercise performance also mentioned suma ecdysterone [ ]. Unfortunately, the initial work was available in obscure journals with sub-standard study designs and presentation of results.

In , Wilborn and coworkers [ ] completed what remains as the only study in humans to examine the impact of ecdysterones while resistance training. Ecdysterones are not recommended for supplementation to increase training adaptations or performance.

Fenugreek trigonella foenum-graecum is an Ayurvedic herb historically used to enhance masculinity and libido.

Fenugreek extract has been shown to increase testosterone levels by decreasing the activity of the aromatase enzyme metabolizing testosterone into estradiol [ , ]. Initial research by Poole et al. After 8 weeks of supplementing and resistance training, significantly greater improvements in body fat, lower body strength, and upper body strength were observed.

Wankhede and colleagues [ ] reported a significant increase in repetitions performed to failure using the bench press and a reduction in body fat when mg Fenugreek extract was consumed while following a resistance training program.

Initial research using Fenugreek extract suggests it may help improve resistance-training adaptations, but more research in different populations is needed before any further recommendations can be made. Gamma oryzanol is a mixture of a plant sterol and ferulic acid theorized to increase anabolic hormonal responses, strength and muscle mass during training [ , ].

Although data are limited, one study reported no effect of 0. Most recently, Eslami and colleagues [ ] supplemented healthy male volunteers with either gamma oryzanol or placebo for 9 weeks while resistance training.

In this study, changes in body composition were not realized, but a significant increase in strength was found in the bench press and leg curl exercise. With limited research of mixed outcomes at this point, no conclusive recommendation can be made at this time as more research is needed to fully determine what impact, if any, gamma oryzanol supplementation may have in exercising individuals.

Glutamine is the most plentiful non-essential amino acid in the body and plays several important physiological roles [ 74 , , ].

Glutamine has been reported to increase cell volume and stimulate protein [ , , ] and glycogen synthesis [ ]. Initial research by Colker and associates [ ] reported that subjects who supplemented their diet with glutamine 5 g and BCAA 3 g enriched whey protein 40 g during resistance training promoted about a two pound greater gain in muscle mass and greater gains in strength than ingesting whey protein alone.

In contrast, Kerksick and colleagues [ ] reported no additional impact on strength, endurance, body composition and anaerobic power of combining 5 g of glutamine and 3 g of BCAAs to 40 g of whey protein in healthy men and women who resistance trained for 10 weeks.

In addition, Antonio et al. In a well-designed investigation, Candow and co-workers [ ] studied the effects of oral glutamine supplementation combined with resistance training in young adults. Thirty-one participants were randomly allocated to receive either glutamine 0.

The authors concluded glutamine supplementation during resistance training had no significant effect on muscle performance, body composition or muscle protein degradation in young healthy adults.

While there may be other beneficial uses for glutamine supplementation i. gastrointestinal health and peptide uptake in stressed populations [ ] and, as mentioned previously, mitigation of soreness and recovery of lost force production [ ] , there does not appear to be any scientific evidence that it supports increases in lean body mass or muscular performance.

Growth hormone releasing peptides GHRP and other non-peptide compounds secretagogues facilitate growth hormone GH release [ , ], and can impact sleep patterns, food intake and cardiovascular functioning [ ] along with improvements in lean mass in clinical wasting states [ ].

These observations have served as the basis for development of nutritionally-based GH stimulators e. and continue to capture interest by sporting populations for their potential to impact growth hormone secretion, recovery and robustness of training [ ].

Finally, Chromiak and Antonio [ ] reported that oral ingestion of many secretagogues fail to consistently stimulate hormone increases in growth hormone and fail to stimulate greater changes in muscle mass or strength.

Currently, there is no convincing scientific evidence that secretagogues support increases in lean body mass or muscular performance. Isoflavones are naturally occurring non-steroidal phytoestrogens that have a similar chemical structure as ipriflavone a synthetic flavonoid drug used in the treatment of osteoporosis [ , , ].

For this reason, soy protein which is an excellent source of isoflavones and isoflavone extracts have been investigated in the possible treatment of osteoporosis as well as their role in body composition changes and changes in cardiovascular health markers.

In this respect, multiple studies have supported the ability of isoflavone supplementation in older women alone [ ] and in combination with exercise over the course of 6—12 months to improve various body composition parameters [ , , ].

Findings from these studies have some applications to sedentary, postmenopausal women. However, there are currently no peer-reviewed data indicating that isoflavone supplementation affects exercise, body composition, or training adaptations in physically active individuals.

For example, Wilborn and colleagues [ ] reported that 8 weeks of supplementing with isoflavones with resistance training did not significantly impact strength or body composition. OKG via enteral feeding has been shown to significantly shorten wound healing time and improve nitrogen balance in severe burn patients [ , ].

A review by Cynober postulated that OKG may operate as a precursor to arginine and nitric oxide, but the overall lack of efficacy for arginine and other precursors limits the potential of OKG. Because of its ability to improve nitrogen balance, OKG may provide some value for athletes engaged in intense training.

However, no significant differences were observed in lower body strength, training volume, gains in muscle mass, or fasting insulin and growth hormone. Testosterone and growth hormone are two primary hormones in the body that serve to promote gains in muscle mass i.

Testosterone also promotes male sex characteristics e. Low level anabolic steroids are often prescribed by physicians to prevent loss of muscle mass for people with various diseases and illnesses [ , , , , , , , , , , , ]. Research has generally shown that use of anabolic steroids and growth hormone during training can promote gains in strength and muscle mass [ , , , , , , , , , , , , ].

However, a number of potentially life threatening adverse effects of steroid abuse have been reported including liver and hormonal dysfunction, hyperlipidemia high cholesterol , increased risk to cardiovascular disease, and behavioral changes i.

Some of the adverse effects associated with the use of these agents are irreversible, particularly in women [ ]. For these reason, anabolic steroids have been banned by most sport organizations and should be avoided unless prescribed by a physician to treat an illness.

Prohormones e. are naturally derived precursors to testosterone or other anabolic steroids. Their use has been suggested to naturally boost levels of these anabolic hormones. While data is available demonstrating increases in testosterone [ , ], virtually no evidence exists demonstrating heightened training adaptations in younger men with normal hormone levels.

In fact, most studies indicate that they do not affect testosterone and that some may actually increase estrogen levels and reduce HDL-cholesterol [ , , , , , , , ]. On a related note, studies have examined the ability of various ingredients to increase testosterone via inhibition of aromatase and 5-alpha-reductase [ ].

Rohle et al. Consequently, although there may be some potential applications for older individuals to replace diminishing androgen levels, it appears that prohormones have no training value. Use of nutritional supplements containing prohormones will result in a positive drug test for anabolic steroids.

Use of supplements knowingly or unknowingly containing prohormones have been believed to have contributed to a number of recent positive drug tests among athletes.

Consequently, care should be taken to make sure that any supplement an athlete considers taking does not contain prohormone precursors particularly if their sport bans and tests for use of such compounds.

Companies such as Informed Choice www. org and National Sanitation Foundation, NSF aka, NSF Certified for Sport www.

org have developed assurance programs to test and screen various nutrition products. It is noteworthy to mention that many prohormones are not lawful for sale in the USA since the passage of the Anabolic Steroid Control Act of The distinctive exception to this is dehydroepiandrosterone DHEA , which has been the subject of numerous clinical studies in aging populations.

Myostatin or growth differentiation factor 8 GDF-8 is a transforming growth factor known as a negative regulator of skeletal muscle hypertrophy [ ]. Since , no additional research has been published that examined the impact of any nutritional ingredient or strategy to inhibit myostatin expression.

In humans, myostatin clearly plays a role in regulating skeletal muscle mass. For example, a study by Ivey and colleagues [ ] reported that female athletes with a less common myostatin allele experienced greater gains in muscle mass during training and reduced atrophy during detraining.

Interestingly, no such changes were reported for men. These results were corroborated by Wilborn et al. As it stands, there is currently no published data supporting the use of sulfo-polysaccharides or any other ingredient touted to act as a myostatin inhibitor for their ability to increase strength or muscle mass.

Consequently, tribulus is marketed as a supplement that can increase testosterone and promote greater gains in strength and muscle mass during training. In human research models, several studies have indicated that tribulus supplementation alone [ , ] or in combination with other segragotogues and androgen precusors [ , ] appears to have no effects on body composition or strength during resistance training.

Vanadyl sulfate is a trace mineral that has been found to affect insulin-sensitivity similar to chromium and may affect protein and glucose metabolism [ , ].

In this regard, reports have highlighted the potential efficacy and support for vanadium to improve insulin sensitivity [ ] and assist with the management of diabetes [ ]. In relation to its potential ability to impact protein and glucose metabolism, vanadyl sulfate supplementation has been purported to positively impact strength and muscle mass [ 74 , ].

However, no studies are available that support the ability of vanadyl sulfate supplementation to impact strength or muscle mass in non-diabetic individuals who are currently resistance training [ , ]. The main ingredients in ZMA formulations are zinc monomethionine aspartate, magnesium aspartate, and vitamin B ZMA supplementation is based upon the rationale that zinc and magnesium deficiency may reduce the production of testosterone and insulin like growth factor IGF Consequently, ZMA supplementation is advocated for its ability to increase testosterone and IGF-1, which is further suggested to promote recovery, anabolism, and strength during training.

Two studies with contrasting outcomes have examined the ability of acute ZMA administration to increase anabolic hormone concentrations. Initially, Brilla and Conte [ ] reported that a zinc-magnesium formulation increased testosterone and IGF-1 two anabolic hormones leading to greater strength gains in football players participating in spring training while Koehler et al.

Wilborn et al. It is noted that previous deficiencies in zinc may negatively impact endogenous production of testosterone secondary to its role in androgen metabolism and steroid receptor interaction [ ].

To this point, Brilla and Conte [ ] did report depletions of both zinc and magnesium, thus increases in testosterone levels could have been attributed to deificient nutritional status rather than a pharmacologic effect.

More research is needed to further evaluate the role of ZMA on body composition and strength during training before definitive conclusions can be drawn. Several nutritional supplements have been proposed to enhance exercise performance.

Throughout this section, emphasis is placed upon results that directly measured some attribute of performance. In situations where a nutrient is purported to stimulate increases in fat-free mass and enhance performance i.

ß-alanine, a non-essential amino acid, has ergogenic potential based on its role in carnosine synthesis [ 12 ]. Carnosine is a dipeptide comprised of the amino acids, histidine and ß-alanine, that naturally occur in large amounts in skeletal muscles. Carnosine is believed to be one of the primary muscle-buffering substances available in skeletal muscle.

Studies have demonstrated that taking four to 6 g of ß-alanine orally, in divided doses, over a day period is effective in increasing carnosine levels [ , ], while more recent studies have demonstrated increased carnosine and efficacy up to 12 g per day [ ].

According to the ISSN position statement, evaluating the existing body of ß-alanine research suggests improvements in exercise performance with more pronounced effects on activities lasting one to 4 min; improvements in neuromuscular fatigue, particularly in older subjects, and lastly; potential benefits in tactical personnel [ 12 ].

Other studies have shown that ß-alanine supplementation can increase the number of repetitions one can do [ ], increase lean body mass [ ], increase knee extension torque [ ], and increase training volume [ ]. In fact, one study also showed that adding ß-alanine to creatine improves performance over creatine alone [ ].

See below for more specific information on what foods to include. When you do not get enough calories from carbohydrate, fat and protein, your performance may not be the best it could be. Then choose a few extra servings of carbohydrate-rich foods throughout the day before playing sports or exercising.

Getting enough carbohydrates helps you have enough glycogen fuel for your body stored to provide you with energy for your training session or sport. Each of these is about 1 serving of carbohydrates:.

The number of extra servings you need will depend on your weight and the type of sport or exercise you are doing. Heavier athletes need more servings than lighter athletes.

Check with your dietitian for personalized recommendations. Many people think they need more protein, but usually this is not the case. You may need more protein if you exercise regularly and intensely or for longer sessions, or if you are trying to build muscle mass. Connect with a dietitian to find out how much protein is right for you.

You can get more protein by eating a few extra servings of protein foods throughout the day. Divide your protein into 3 to 4 meals and snacks throughout the day and try to include a variety of protein sources.

Sources of protein include beans, legumes, tofu, tempeh, edamame, nuts and seeds and their butters, eggs, meat, chicken, fish, dairy products like milk, cheese and yogurt, and fortified plant-based beverages. About 1 to 4 hours before playing sports, eat a meal that is rich in carbohydrate, low in fat and fairly moderate or low in protein and fibre for quick digestion and to prevent gastrointestinal discomforts while playing or training.

Here are some examples:. Your portion size will depend on how intense or long your training session will be and your body weight.

Choose smaller meals that are easier to digest closer to the time you will be exercising. During sports, training or exercise that last longer than 1 hour, your body needs easy-to-digest foods or fluids.

Your best approach is to drink your carbohydrate in a sports drink or a gel, but for longer exercise sessions of 2 hours or more, additional solid carbohydrates may be needed like fruit, crackers, a cereal bar, yogurt or a smoothie. Connect with a dietitian to find out how many grams of carbohydrate you should aim for while exercising.

The amount you need depends on the type of activity, your body size and the duration of your activity.