Protein with a Purpose: Powerful Nutrition for All Exercisers

The protein needs of athletes is a common point of disagreement among nutrition professionals. In response, many established researchers have investigated this question in controlled clinical trials. A summary of the evidence presented by the the National Diary Council (NDC) in a whey protein booklet highlights the importance of high-quality protein for exercisers, older people and individuals on a reduced-energy diet. The article references a recent position of the American College of Sports Medicine (ACSM), the American Dietetic Association (ADA), and the Dietitians of Canada (DC) where exercise nutrition authorities agree that regular exercisers may benefit a protein intake that is up to two times greater than the American RDA (0.8g/kg or 0.36g/lb).

Skeletal muscle is degraded by both endurance and strength exercises. Intuitively, it seems that athletes of both kinds, for example runners and powerlifters, may need extra protein to compensate for the demands of exercise-- a lot of research supports this notion. After endurance or resistance training, the exerciser may require a protein intake that is up to two times the RDA value to maximize skeletal muscle mass and achieve peak performance. The following are the protein recommendations (in grams of protein per each lb or kg of body weight) that may be appropriate for different types of exercisers:

A recreational exerciser: 0.5-0.7 g/lb (1.1-1.54g/kg)

An endurance athlete: 0.5-0.8 g/lb (1.1-1.76g/kg)

A strength training athlete: 0.5-0.8 g/lb (1.1-1.76g/kg)

An athlete restricting calories: 0.8-0.9 g/lb (1.76g/kg-1.98g/kg)

For example, the RDA for a 180 pound strength-trained athletes is about 65g/day. A dietary protein intake of 65g/day may be acheived by eating about 8 oz of boneless/skinless chicken breast, for example. On the other hand, both endurance and strength athletes weighting about 180 lb (~82 kg) may require between 90g/day and 144g/day of daily protein. The 90g/day to 144g/day protein recommendation may be met by eating between 11 oz and 18 oz of chicken breast or about four to seven 1-oz scoops of whey protein. In order to maintain skeletal muscle, up to 0.9g of protein per pound of body weight may be beneficial for an athletic individual consuming a reduced-calorie diet. Given that gymnasts, rowers, wrestlers, bodybuilders, powerlifters often utilize lower-calorie meal plans, a higher protein diet may be valuable for these individuals.

Though protein is recognized for its role in maintaining and repairing skeletal muscle tissue,some amino acids may also influence metabolic processes. For example, research performed by DK Layman and his colleagues demonstrates that the essential branched chain amino acid leucine, plentiful in whey protein, signals structural protein synthesis. Leucine appears to “turn on” the muscle-building machinery in the body, in addition fueling muscle during exercise and serving as a structural component of muscle.

The overall amount of protein is important, but the quality of dietary protein is also of consequence. High-quality or “complete” dietarty proteins are usually extracted from animal sources. Most vegetable proteins, like those coming from beans, grains and nuts, do not contain all of the needed parts and must be carefully “complemented” to be complete. Furthermore, plant proteins are generally low in signaling proteins, like leucine. If you are a vegetarian, soy is a good source of plant-based protein. Also, this chart is a helpful guide for meal-planning with the use of complementary proteins.

In conclusion, both competitive and recreational exercisers may benefit from dietary protein intake that is up to two times greater than the RDA. High quality dietary proteins include lean meat, low-fat dairy, poultry, eggs and whey powder.

Dr. Jean Gutierrez currently serves as a Visiting Assistant Professor of Exercise Science at The George Washington University. You may contact her directly at escjlj@gwumc.edu