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For bodybuilders engaged in a progressive resistance training program, protein-rich foods are quickly identified and desired for packing on muscle. For anyone engaged in routine physical activity, protein is one of the most popular dietary supplements today, for building up the body’s force-producing abilities. Media reports have suggested that chronically high protein intake can cause unnecessary stress on the body’s filtering processes. However, these reports are often based on non-human subjects, inactive people, and persons with impaired renal function. For healthy, active men and women, an increase in dietary proteins can safely and effectively improve exercise performance by enhancing energy and increasing muscle mass.

Human muscle fiber counts vary greatly between two individuals. Fiber numbers change very little as a result of routine exercise or other environmental triggers. Aerobic (running, cycling) and resistance training (anaerobic) will increase fiber size and subsequent force producing capabilities. An increase in muscle cross-sectional area benefits overall body composition by increasing lean body mass while decreasing fat mass. To increase muscle mass, protein anabolism must exceed muscle catabolism. Resistance training programs are always able to increase protein synthesis – studies demonstrate increases up to 182 percent over baseline. Resistance training is an excellent way to increase muscle, so long as the increased protein demands are properly met.

The U.S. recommended dietary allowance for protein intake is 0.8 to one gram per kilogram of bodyweight for healthy, moderately active people. However, many athletes tend to eat much more than this – regularly increasing their dietary intake using protein-based supplements. Several studies have examined the efficiency of increases in dietary protein. In 2005, the American Journal of Physical Endocrinology and Metabolism published research that demonstrated that 1.2 grams of whey protein isolates per kilogram, consumed around resistance training, resulted in a an almost two-fold increase in lean body mass, as compared to a carbohydrate supplemented group.

The International Society of Sports Nutrition published an official stand regarding protein and exercise in September 2007. Researchers explain the increased need for protein for active people – far exceeding the U.S. RDA. According to the ISSN, exercising individuals should consume 1.4 to 2 grams of protein per kilogram, per day. Endurance athletes should consume at the lower level of this range. Intermittent athletes – such as soccer, basketball, martial arts – should ingest levels at mid-range amounts. Strength and power athletes – bodybuilders and powerlifters – must consume at the upper levels to provide enough substrate for optimal repair and growth of muscle tissue. The position stand further recommends exercising individuals to consume high-quailty proteins within the time period encompassing the exercise session – before, during and after. However, they assert more research is needed to ascertain the affects of protein timing for activities other than resistance training.

In November 2005, Melvin Williams published a study in the ISSN journal that examined the affects of amino acid supplements in sports performance. Williams concluded that the consumption of protein as high as 2.8 grams per kilogram, per day, by well-trained athletes does not negatively affect healthy individuals. It may impair renal function in athletes with preexisting health conditions, such as diabetes mellitus and those predisposed to kidney disease and stones.

Proteins dissected

Amino acids are the building blocks of proteins. Complete proteins contain a full spectrum. Specific amino acids have been theorized to enhance performance in a number of ways, such as increasing the secretion of anabolic hormones, modifying fuel use during exercise, preventing adverse effects of overtraining and preventing central fatigue. There are nine essential amino acids that must be obtained through the diet to maximize protein anabolism; these include: iso-leucine, leucine, lysine, threonine, tryptophan, methionine, histidine, valine and phenylalanine. Other non-essential amino acids can be derived from within the body if a deficiency occurs; of these, arginine, cysteine, glycine, glutamine and tyrosine are considered conditionally essential – they are not normally required through the diet but certain requirements can exceed what can be synthesized endogenously.

Branched chain amino acids – leucine, iso-leucine and valine – are three essential organic protein molecules that comprise a third of the human body’s skeletal muscle and almost a half of the dietary requirement for essential amino acids. During exercise, they represent almost a quarter of the protein broken down from muscle. BCAA supplements have a lot of clinical support for enhancing physical performance by promoting positive protein synthesis and combating central fatigue. Leucine, in particular, has increasing support for its role in stimulating protein synthesis and inhibiting degradation.

Protein must be absorbed and partitioned properly for an ergogenic affect. The amino acid bioavailability of a protein source is best summarized by the amount and variety of amino acids that are digested and absorbed into the blood stream. Nitrogen-balance studies further support these findings by comparing the nitrogen content of an ingested protein to that of the subsequent nitrogen content found in the excreted feces. The impact on target tissues can also be taken into consideration. The U.S. Dairy Export Council’s 2003 Reference Manual for U.S. Whey and Lactose Products, states milk-derived whey protein isolate has the highest protein digestibility score out of all common protein sources due to its high content of essential and branched-chain amino acids. Whey protein is especially rich in leucine; up to 14 grams per 100 grams.

Aside from whey, milk-derived casein and egg white powder are also classified for their superior quality and full spectrum of amino acids. Rating poorly at the bottom: canned lentils, peanut meal and wheat gluten. In today’s booming sports supplement industry, whey and casein are the two most popular types of proteins offered in commercially available dietary supplements.

Protein requirements for strength training

Bodybuilders and powerlifters often report the positive results of a high-protein diet augmented by protein supplements. Based on the ISSN recommendations, strength athletes should consume around two grams of protein per kilogram, per day. A 220-pound bodybuilder should target a daily protein intake of 200 grams, whereas reports also suggest up to 280 grams is still tolerable in healthy athletes. Concurrent fat and carbohydrate should also be considered. A strength athlete’s increased ingestion of this vital macro nutrient is required due to an increase in intramuscular protein oxidation and breakdown during a progressive resistance training cycle. As a result of intense exercise, the body enters a state of negative nitrogen balance, meaning more protein is being broken down than synthesized. Studies suggest that muscle protein breakdown can remain elevated for up to 48 hours after exhausting resistance exercise. During this time, the body is at a primed state to partition dietary protein toward muscle hypertrophy. To accumulate greater musculature, protein is needed to fuel synthesis and slow down enzymes, and other agents, that accelerate protein breakdown.

It’s been widely accepted that athletes of all types need to increase their protein intakes to maximize their physical recovery and subsequent performance abilities. Whole food choices should always be the primary method for increasing protein intake. To further fill in nutritional holes, whey and casein proteins dominate most of today’s research – from credible scientific trials and theories, to subjective recommendations offered by the enduring efforts of successful bodybuilders and powerlifters.

Roth, Erich. Skeletal muscle gain: how much can be achieved by protein and amino acid administration? Current Opinion in Clinical Nutrition & Metabolic Care. 11(1):32-33, January 2008.

Campbell B, Kreider RB, Ziegenfuss T, La Bounty P, Roberts M, Burke D, Landis J, Lopez H, Antonio J. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2007 Sep 26;4:8.

Melvin Williams. Dietary Supplements and Sports Performance: Amino Acids. Exercise Science, Sport, Physical Education, and Recreation, Old Dominion University, Norfolk, VA J Int Soc Sports Nutr. 2005; 2: 63–67.

Bolster DR, Pikosky MA, Gaine PC, Martin W, Wolfe RR, Tipton KD, Maclean D, Maresh CM, Rodriguez NR. Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise. Am J Physiol Endocrinol Metab. 2005;289:E678–83.

Raymond Zimmer (2005) “Whey Protein- The Role of Protein Supplementation in Resistance Training“, Nutrition Bytes: Vol. 10: No. 2, Article 1.

Nutritional Properties of Whey and Lactose Products. Reference Manual for U.S. Whey and Lactose Products. The U.S. Dairy Export Council, Washington, D.C. April 2003