Cai Z, Liu X, Pang X. Effects of whey protein supplementation on exercise capacity and fatigue resistance. Med Sport ; DOI: English Italian Login Search. ISSUES AND ARTICLES Articles online first Current issue Past issues Most read ABOUT THIS JOURNAL Editorial Board Contact the journals department Recommend to your librarian FOR AUTHORS Publishing options Instructions to authors Peer-Review policy Online submission Publication ethics Self-archiving policy SUBSCRIBE To subscribe Activate your subscription View your subscription JOURNAL TOOLS Publishing options eTOC To subscribe Submit an article Recommend to your librarian ARTICLE TOOLS Publication history Reprints Permissions Cite this article as Share.

MEDICAL AREA Medicina dello Sport June;75 2 DOI: Publication History Issue published online: July 4, Manuscript accepted: May 26, Manuscript received: April 30, Cite this article as Cai Z, Liu X, Pang X. JOURNAL TOOLS. Publishing options. She recommends grabbing a recovery drink within 30 minutes of finishing your workout session.

RELATED: 3 Easy Ways to Speed Up Recovery. For many cyclists, building muscle is not necessarily their first priority. At the same time, you still need to build muscle to ride well. Not only does heavy training break down muscle fibers, but also also you need to maintain healthy muscle tissue to produce that hill-crushing, sprint-winning wattage.

Protein is a significant source of amino acids, which provide the ingredients for muscle growth. There are over 50 amino acids found in nature and of these, nine are essential to the human body.

The body can extract amino acids from animal proteins and some forms of plant protein , such as soy. Protein Intake for Seniors.

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A team of NIH researchers led by Drs. Paul Hwang, Avindra Nath, and Brian Walitt have been studying a woman who took days to recover after physical exertion and several of her relatives at the NIH Clinical Center.

Their findings were published on August 22, , in the Proceedings of the National Academy of Sciences. Tests done while the woman was exercising found a very slow recovery of cellular energy production after exertion.

Muscle cells taken from the patient and examined in the lab showed reduced oxygen use. Oxygen is used by mitochondria, the cell compartment that makes energy molecules. Further laboratory studies led the team to a protein called WASF3.

Blocking WASF3 allowed mitochondria to produce energy at normal levels. The team then showed that extra WASF3 in the cells interfered with formation of the structures that mitochondria use to produce energy.

To better understand the role of WASF3, the team engineered mice to produce excess WASF3. They found that, similar to people with post-exertional malaise, muscles in these mice were slow to recover after exercise.

This dysfunctional increase in WASF3 seemed to be linked to impairment of a cellular signaling pathway called the ER stress pathway. When the team treated human muscle cells with a compound known to increase ER stress, they saw a corresponding harmful increase in WASF3. The researchers treated cells from the initial study participant with an experimental drug, called salubrinal, known to reduce ER stress.

After this treatment, WASF3 levels decreased in the cells, more mitochondrial energy complexes formed, and energy production improved. Mitochondrial dysfunction has been found in some people with Long COVID and other conditions that include fatigue.

More research is needed to understand whether targeting ER stress may also be a promising approach for these conditions. Wang PY, Ma J, Kim YC, Son AY, Syed AM, Liu C, Mori MP, Huffstutler RD, Stolinski JL, Talagala SL, Kang JG, Walitt BT, Nath A, Hwang PM. Proc Natl Acad Sci U S A. doi: More refined carbohydrate foods such as white bread, jams and lollies are useful to boost the total intake of carbohydrate, particularly for very active people.

Athletes are advised to adjust the amount of carbohydrate they consume for fuelling and recovery to suit their exercise level. For example:. A more recent strategy adopted by some athletes is to train with low body carbohydrate levels and intakes train low. There is accumulating evidence that carefully planned periods of training with low carbohydrate availability may enhance some of the adaptations in muscle to the training program.

However, currently the benefits of this approach to athletic performance are unclear. The GI has become of increasing interest to athletes in the area of sports nutrition. However, the particular timing of ingestion of carbohydrate foods with different GIs around exercise might be important.

There is a suggestion that low GI foods may be useful before exercise to provide a more sustained energy release, although evidence is not convincing in terms of any resulting performance benefit.

Moderate to high GI foods and fluids may be the most beneficial during exercise and in the early recovery period. However, it is important to remember the type and timing of food eaten should be tailored to personal preferences and to maximise the performance of the particular sport in which the person is involved.

A high-carbohydrate meal 3 to 4 hours before exercise is thought to have a positive effect on performance. A small snack one to 2 hours before exercise may also benefit performance. It is important to ensure good hydration prior to an event.

Consuming approximately ml of fluid in the 2 to 4 hours prior to an event may be a good general strategy to take.

Some people may experience a negative response to eating close to exercise. A meal high in fat, protein or fibre is likely to increase the risk of digestive discomfort.

It is recommended that meals just before exercise should be high in carbohydrates as they do not cause gastrointestinal upset. Liquid meal supplements may also be appropriate, particularly for athletes who suffer from pre-event nerves. For athletes involved in events lasting less than 60 minutes in duration, a mouth rinse with a carbohydrate beverage may be sufficient to help improve performance.

Benefits of this strategy appear to relate to effects on the brain and central nervous system. During exercise lasting more than 60 minutes, an intake of carbohydrate is required to top up blood glucose levels and delay fatigue.

Current recommendations suggest 30 to 60 g of carbohydrate is sufficient, and can be in the form of lollies, sports gels, sports drinks, low-fat muesli and sports bars or sandwiches with white bread. It is important to start your intake early in exercise and to consume regular amounts throughout the exercise period.

It is also important to consume regular fluid during prolonged exercise to avoid dehydration. Sports drinks, diluted fruit juice and water are suitable choices. For people exercising for more than 4 hours, up to 90 grams of carbohydrate per hour is recommended. Carbohydrate foods and fluids should be consumed after exercise, particularly in the first one to 2 hours after exercise.

While consuming sufficient total carbohydrate post-exercise is important, the type of carbohydrate source might also be important, particularly if a second training session or event will occur less than 8 hours later. In these situations, athletes should choose carbohydrate sources with a high GI for example white bread, white rice, white potatoes in the first half hour or so after exercise.

This should be continued until the normal meal pattern resumes. Since most athletes develop a fluid deficit during exercise, replenishment of fluids post-exercise is also a very important consideration for optimal recovery.

It is recommended that athletes consume 1. Protein is an important part of a training diet and plays a key role in post-exercise recovery and repair. Protein needs are generally met and often exceeded by most athletes who consume sufficient energy in their diet. The amount of protein recommended for sporting people is only slightly higher than that recommended for the general public.

For athletes interested in increasing lean mass or muscle protein synthesis, consumption of a high-quality protein source such as whey protein or milk containing around 20 to 25 g protein in close proximity to exercise for example, within the period immediately to 2 hours after exercise may be beneficial.

As a general approach to achieving optimal protein intakes, it is suggested to space out protein intake fairly evenly over the course of a day, for instance around 25 to 30 g protein every 3 to 5 hours, including as part of regular meals. There is currently a lack of evidence to show that protein supplements directly improve athletic performance.

Therefore, for most athletes, additional protein supplements are unlikely to improve sport performance. A well-planned diet will meet your vitamin and mineral needs. Supplements will only be of any benefit if your diet is inadequate or you have a diagnosed deficiency, such as an iron or calcium deficiency.

There is no evidence that extra doses of vitamins improve sporting performance. Nutritional supplements can be found in pill, tablet, capsule, powder or liquid form, and cover a broad range of products including:.

Before using supplements, you should consider what else you can do to improve your sporting performance — diet, training and lifestyle changes are all more proven and cost effective ways to improve your performance. Relatively few supplements that claim performance benefits are supported by sound scientific evidence.

Use of vitamin and mineral supplements is also potentially dangerous. Supplements should not be taken without the advice of a qualified health professional. The ethical use of sports supplements is a personal choice by athletes, and it remains controversial.

If taking supplements, you are also at risk of committing an anti-doping rule violation no matter what level of sport you play.

Dehydration can impair athletic performance and, in extreme cases, may lead to collapse and even death. Drinking plenty of fluids before, during and after exercise is very important.

Fluid intake is particularly important for events lasting more than 60 minutes, of high intensity or in warm conditions. Water is a suitable drink, but sports drinks may be required, especially in endurance events or warm climates. Sports drinks contain some sodium, which helps absorption.

If your meals leave you feeling hungry, you might need more protein in your diet. According to Griffin, feeling hungry every one to two hours might be a sign that you should add protein to your diet. Try incorporating this delicious organic protein powder into your shakes.

RELATED: 5 Nearly Effortless Ways to Add More Protein to Your Diet. A heavy training schedule combined with work or family life can wear you down.

You may feel tired during the day, and it can be hard to isolate exactly why. The answer might be not enough protein. In addition to its role in recovery, protein helps stabilize blood sugars. Recovery days might mean stretching followed by an easy spin around flat roads or another form of active recovery, such as walking.

Whatever form it takes, you should feel refreshed after a recovery day. Consuming protein within two hours after exercise helps ensure that your body has the resources it needs to repair muscles damaged or stressed by your training efforts.

She recommends grabbing a recovery drink within 30 minutes of finishing your workout session. RELATED: 3 Easy Ways to Speed Up Recovery. For many cyclists, building muscle is not necessarily their first priority.

At the same time, you still need to build muscle to ride well. The supplement did not boost their athletic performance, but the benefits on fatigue suggest it may help athletes recover more quickly from an intense workout.

The findings appear in the International Journal of Sports Medicine. For the study, researchers led by Dr. Claire Thomas, of the Universite Evry Val d'Essonne, recruited 18 physically active young men.

Half were middle- or long-distance runners, and half were recreational athletes. The volunteers were randomly assigned to use either the protein powder or a placebo powder twice a day for 28 days. The protein mix contained a host of amino acids -- the building blocks of proteins -- along with a collection of antioxidants, vitamins and minerals.

The placebo powder contained only flavoring and salts. At the beginning and end of the study period, the men underwent exercise tests on a stationary bike.

After 28 days, men who took the supplement showed no change in their exercise performance relative to the placebo group. 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. Campbell B, Kreider RB, Ziegenfuss T, La Bounty P, Roberts M, Burke D, et al. International society of sports nutrition position stand: protein and exercise.

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