[Adam F]

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.

References
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.