Most coaches, athletes, and bodybuilders don’t like to read scientific studies, review papers or anything containing a bunch of scientific jargon. At the same time these papers can be beneficial in prescribing training, nutrition and supplementation protocols to enhance performance and physique. You might ask is there any way I can get this information without reading these boring papers? Good news. Your savior has arrived. The Practical Scientist column will provide key points from the most prominent scientific training and nutrition research. You won’t have to spend hours looking through papers with long complex words and multiple formulas. I will have already taken care of that task. I will provide readers with the key points and most useful information that can be gathered from the data discussed. The information will be provided in bullet style format. Believe it or not some of us actually like to spend our days reading, analyzing and discussing these papers with scientists, researchers and analytical thinkers. I hope you enjoy the new column. If you have any questions feel free to ask.

In 2003 Tipton and Wolfe presented one of the most comprehensive review papers to date on protein (Protein and amino acids for athletes). The objective of the review was to update the literature since 1991 and critically examine the available information on protein nutrition for athletes. In February of 2007 Tipton wrote another outstanding paper concerning protein and athletes (Protein Requirements and Recommendations for Athletes: Relevance of Ivory Tower Arguments for Practical Recommendations). The focus on this paper was the author’s view of various factors involved in protein nutrition and how they may influence the adaptations that result from training and nutritional intake, and how this information may be used by practitioners, coaches, and athletes to determine appropriate protein intakes during training for optimal competitive results. In this article I will point out some of the key points Tipton revealed in his February 2007 paper.

Key Points from Protein Requirements and Recommendations for Athletes: Relevance of Ivory Tower Arguments for Practical Recommendations, Kevin D. Tipton, PhD, Oliver C. Witard, Msc

In general, scientific opinion on the protein controversy divides itself in two distinct camps- those who believe that exercise and sport increase the bodies demand for protein and those who believe protein requirements for exercising individuals and athletes are no different than the general population.

The demands of training vary within a particular sport or in individuals. Scientific studies often cited in the literature may be irrelevant for athletes, coaches, and nutrition practitioners. My comment: athletes are ultimately concerned with physique and performance not a bunch of scientific jargon.

The camp supporting the need for higher protein for athletes often cites nitrogen balance as an indicator. Numerous well-controlled studies have shown that nitrogen balance in athletes is greater the sedentary control groups. Increased protein needs may come from increased amino acid oxidation during exercise or growth and repair of muscle tissue.

There is no reason to recommend protein supplements per se because there is no evidence that supplements work better than foods

Increased MPS (muscle protein synthesis) is induced after resistance and endurance training (My comment: many endurance athletes do not consider the need for increased mitochondria and mitochondria enzymes which could lead to increased protein needs), suggesting additional protein would be necessary to provide needed amino acids.

The opposing camp argues that exercise, even when of long duration and intensive does not increase the dietary requirement for protein. Their argument is based on the fact that exercise has been shown to increase the efficiency of use of amino acids from ingested protein. Butterfield and others demonstrated this as they showed even at calorie deficits and low protein intakes nitrogen balance was improved with exercise.


A common criticism of studies that show increased use of amino acids with exercise (better utilization with exercise suggesting no need for higher intakes, more efficient shuttling to skeletal muscle) is that intensity or duration of exercise is not as great as that practiced by top athletes.

It has also been reported that low intensity endurance and resistance exercise does not stimulate protein synthesis. My comment: I guess it depends on what the definition of low intensity means. Studies indicate 40% (occlusion)- 130% of 1rm stimulates MPS relatively the same when total work is equal.

Arguments against higher protein requirements are based on difficulties showing increased muscle mass at higher levels of protein intake. When the increases in nitrogen balance are extrapolated to gains in lean body mass, the numbers don’t match. Gains of 200-500grams per day of lean body mass are physiologically impossible. Results suggest that nitrogen balance methods tend to overestimate nitrogen balance (My comment: among other problems with nitrogen balance studies) at high intakes. There are definitely studies providing evidence for higher protein needs for athletes as well as studying supporting the opposite.

Testing fallacies remain partly responsible for difficulties in determining protein requirements for athletes. In terms of design most studies use measurements of nitrogen losses or tracer-labeled amino acid oxidation rates.

In general, Nitrogen balance techniques are most commonly used to estimate protein requirements. A positive nitrogen balance indicates an anabolic situation while a negative nitrogen balance indicates protein catabolism. My comment: this procedure does not necessarily indicate where protein is going to and coming from, implications for MPS or breakdown limited. Healthy adults who are not growing are generally in nitrogen balance.

Nitrogen balance data is subject to numerous problems. Limitations have been well covered in previous papers and studies. One of the key criticisms of nitrogen balance studies is a lack of sensitivity because it involves only gross measures of nitrogen intake and excretion. My comment: was never intended to determine needs of bodybuilders or other athletes.

Nitrogen balance studies for strength athletes may be particularly inappropriate. The goal for a strength athlete is to increase lean body mass, strength and size. Nitrogen balance is not enough, as the goal would be inducing a positive nitrogen balance.

Establishing nitrogen balance for endurance athletes may not be appropriate either; as this could lead to a compromise in the up-regulation of enzyme activity, capillarization, or mitochondrial biogenesis after endurance training (positive nitrogen balance would be necessary to compensate for these needs).

As mentioned earlier nitrogen balance and stable isotope studies are of great interest to scientists, but from a practical standpoint coaches and athletes are generally not concerned with scientific debate. Performance is the ultimate outcome that interest athletes. Numerous authors have made this point. Millward stated, “Thus, the key test of adequacy of either protein or amino acid intake must be the long-term response in terms of the specific function of interest”.

It doesn’t seem optimal to suggest a given protein intake to broad category of athletes (strength or endurance athletes). Many sports require both strength and endurance. Consider a decathlete that participates in varied training and requires a multitude of motor qualities. Gender should also be considered. Protein recommendations should be based on individual circumstances. My comment: this would include different intakes for athletes participating in the same sport as their needs still vary.

Even if higher protein requirements for athletes are correct as some scientists indicate the argument is irrelevant because most athletes take in more protein than even the highest suggestions. My comment: the range given is generally 1.2-2gms/ kg/- bodyweight, I know many athletes who double or in some cases go even higher than double this amount. These athletes are at minimal risk for protein deficiency assuming that a maintenance level of calories are consumed an adequate nutritional practices are followed.

Tarnopolsky has suggested about 20% of athletes may consume levels of protein below recommended requirement for sedentary individuals. These individuals may be at risk for protein deficiencies. These athletes include vegetarians, weight class athletes, athletes suddenly increasing activity levels, and individuals under going weight loss programs. My comment: particularly people following rapid weight loss programs may be at risk for protein deficiencies as well as other problems. Rapid weight loss is not uncommon for athletes. I have seen numerous combat athletes drop over 20lbs in three days.


Vegetarian diets are plant based, thus the quality of ingested protein may be questioned. A sufficient amount of amino acids can be supplied by plant foods alone, if a variety of foods are consumed, and eaten together, and energy intake is sufficient. My comment: As an example, when grains are eaten with legumes, the protein becomes non-limiting. Grains are low in lysine but high in methionine while legumes are low in methionine but high in lysine. This method is often termed protein combining. A big concern, are individuals who avoid all animal protein sources (vegans). There is a good chance if diet is too restricted as with many vegans numerous micronutrient and protein deficiencies can occur.

If the diet predominantly contains foods of lower protein quality this may increase the total amount of protein needed (generally refers to vegetarian based diets. My comment: I have seen very few athletes who seem to do well on a vegetarian type diet. My suggestion is consume adequate amounts of lean meats with low fat dairy products.

Calorie intake plays a key role in determining protein requirements. My comment: higher caloric intake generally means you need to consume less protein. Early studies showed that athletes gain strength and maintain muscle mass even during periods of low protein intake, assuming caloric intake is sufficient.

Many athletes attempt to drop bodyweight while maintaining or minimizing loss of lean mass. Numerous studies support the role for higher protein diets under these conditions. My comment: studies indicate huge losses in bodyweight while maintaining bodily proteins if protein intake is sufficient. Suggestions vary for what is sufficient as this depends on a multitude of factors. I have seen cases where athletes actually gain skeletal muscle while losing body fat. Keep in mind under most circumstances the simultaneous gain of skeletal muscle and loss of body fat does not occur, but it seems to occur often in obese newbie trainees, and individuals who increase protein intake substantially above previous levels. In fact, I had a female figure competitor who recently dropped a significant amount of body fat while simultaneously increasing muscle tissue. I would think this was due to her drastic change in diet. Her previous diet was the typical American diet while her pre-comp diet was substantially higher in protein, moderate in carbs and fat, and relatively high in fiber. She reported feeling better, getting stronger, and she definitely looked better although her calorie intake was about 20% below her calculated maintenance level. The last bodybuilding show I competed in I experienced similar results in the first 4-5 weeks of my pre-comp diet.

On a whole body-level, studies suggest that although vegetarian diets may be sufficient for positive nitrogen balance, reliance on animal proteins results in superior balance. Although a study by Jannelle stated the clear superiority of animal proteins might not be so clear.

A problem with whole-body studies is they do not give a clear picture of the importance of protein intake to other tissues, particularly muscle. In a series of experiments using stable isotopes is has been determined in general, use of amino acids from animal proteins (milk) is greater than plant proteins (wheat). This suggests that amino acids from different sources may be utilized by different tissues. Amino acids ingested as milk proteins are taken up in greater amounts by peripheral (muscle) rather the splanchnic tissues (visceral or relating to visceral).

Phillips and colleagues reported that uptake of amino acids from milk proteins into muscle is greater than from soy protein after resistance exercise. One a muscle level after resistance exercise, the differences in amino acid uptake between casein and whey proteins are unclear. My comment: there is research that supports the superiority of both proteins in regards to net muscle protein balance. I would suggest consumption of both proteins. Both proteins have their benefits and can be beneficial to athletes.

At rest, carbohydrate consumption with protein increases whole body amino acid retention. It has been shown that carbohydrate ingestion increases the use of amino acids after resistance exercise, an effect likely contributed to the insulin response. My comment: if insufficient amino acids are present insulin will not promote MPS.

In a previous study the anabolic response to a solution of EAA and carbohydrates immediately before exercise was approximately three times greater than when the solution was ingested after exercise. In a more recent study using and identical protocol, the response to an ingestion of whey proteins immediately before exercise was similar to that after exercise. My comment: this study conducted by Tipton showed that the response was different for an intact protein than an EAA and carbohydrate solution. Tipton suggested the results might have been different if the whey had been consumed further in advance before the workout. Consuming the whey one hour before workout would have allowed a peak in blood amino acid levels as the workout began.


Do changes in metabolism during short term studies correlate with long-term changes that may affect adaptations to protein ingestion? Wolfe’s laboratory suggests results from acute studies are representative of those that may occur over longer periods of training. In a recent study, we found the response of NBAL (net muscle protein balance) to resistance exercise and EAA was similar before and after 16 weeks of training. Thus, acute studies can be used to determine protein ingestion over longer periods. Phillips and colleagues reported that the anabolic response of muscle NBAL to ingestion of milk and soy protein after exercise predicted the accumulation of muscle mass in healthy young volunteers over a 12 week-period.

My thoughts: The paper is an excellent referral source for coaches and athletes. Many practical topics are discussed in the paper. As you can see from briefly looking at reports from various studies both camps have valid points, but as Tipton implied athletes are generally not concerned with scientific findings and debate. Athletes are concerned with performance (there is definitely a lack of scientific data exploring protein effects on performance). Anecdotal evidence suggests that athletes benefit from higher protein intakes than sedentary individuals. An ample amount of scientific evidence also suggests that protein needs are higher for athletes than suggestions made by RDA (.8 gm/kg/bodyweight per day). The amount above that level necessary to optimize MPS is debatable.

A topic most people seem to forget about is protein intake and general health. In some cases moderate to high protein intake has been shown to enhance Insulin sensitivity, increase weight loss, increase satiation, provide valuable micronutrients, enhance blood lipid profiles, increase bone health (when adequate calcium is ingested) and increase thermogenesis. Protein serves more purposes than just increasing skeletal muscle tissue. Enzymes, hormones, immuno-globulins, and blood transporters are made up of proteins.

We know too little protein can be detrimental while we are not sure of exactly how much protein is needed to maximize performance and physique. Unless you have renal problems or amino acid oxidations disorders (phenylketonuria, Maple syrup urine disease, etc…) it may not be necessary to place limits on dietary protein intake. At the same time once a ceiling is reached protein intake above that level will probably just result in increased amino acid oxidation and ureagenesis (formation of urea- urea is end product of amino acid catabolism formed in liver. The cycle takes place in the liver where toxic ammonia is prepared for safe travel through the blood and is then excreted by the kidney.) Once again ample protein is needed to increase MPS, but I doubt if an 187lb individual really needs 450gms of protein to support MPS (I mention this as I seen it in a popular magazine the other day).

Before I sign off I would like to touch on the subject of heightened protein intake and kidney function. How many times have you heard that too much protein will destroy your kidneys? This is a common statement heard when speaking of high protein diets. You would think there should be mounds of evidence indicating this. After all, my doctor or dietitian said so. Like many other statements concerning nutrition, the above statement cannot be verified by scientific or practical study. I have known hundreds of people who consume 300–400 grams of protein a day. Guess what? No kidney problems. I have searched through a multitude of studies and spoke to numerous coaches, scientists and nutrition consultants around the world, and the resounding conclusion has been the same. There is no evidence whatsoever that protein intake causes kidney damage in individuals with normal renal functioning (Hale, 2007 Protein Essentials).

In a paper taking an in depth look at protein and it’s effect on kidney function Martin and colleagues concluded that: “Although excessive protein intake remains a health concern in individuals with preexisting renal disease, the literature lacks significant research demonstrating a link between protein intake and the initiation or progression of renal disease in healthy individuals. More importantly, evidence suggests that protein-induced changes in renal function are likely a normal adaptative mechanism well within the functional limits of a healthy kidney. Without question, long-term studies are needed to clarify the scant evidence currently available regarding this relationship. At present, there is not sufficient proof to warrant public health directives aimed at restricting dietary protein intake in healthy adults for the purpose of preserving renal function.” Poortmans and Skov also conducted studies that showed high dietary protein intake does not damage kidney function in individuals with normal kidney functioning.

On a final note, I am in agreement with Tipton who suggested in his 2003 paper that it’s better to eat a little too much protein than be on the other end and eat too little (which definitely causes numerous problems). Don’t be afraid to use science in conjunction with your own personal experiments in determining your own personal protein needs.

I hope you enjoyed the first edition of The Practical Scientist. Tune in next time when we take a further look into the wonderful world of Science.


Hale, J. (2007). Protein Essentials. MaxCondition Publishing.

Tipton, KD. Witard, OC. (2007) Protein Requirements and Recommendations for Athletes: Relevance of Ivory Tower Arguments for Practical Recommendations. Clinics In Sports Medicine.

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