There are many myths and misconceptions regarding optimum protein intake and the effects of protein on body composition, performance, recovery and metabolism.
The International Society of Sports Nutrition (ISSN) developed a position on protein and exercise. The following is a summary of some of the research from leaders in the field of sports nutrition - as well as NASM's own nutrition certification program.
- Research supports that individuals engaged in regular exercise training require more dietary protein than sedentary individuals.
- Protein intake of 1.4 – 2.0 g/kg/day for physically active individuals is safe, and may improve adaptations to exercise training.
- Protein intake at this level is not detrimental to kidney function or bone metabolism in healthy, active persons when part of a balanced, nutrient-dense diet.
- Daily protein requirements can be met through a varied, regular diet.
- Supplemental protein, e.g. protein powders, are a practical way of ensuring adequate and quality protein intake for athletes.
- The quality of protein can vary depending upon the source. This can affect amino acid bioavailability and recovery and/or training adaptations.
- Optimum timing of protein intake is essential for proper recovery, immune function, and the growth and maintenance of lean body mass.
- Branched-chain amino acids (leucine, isoleucine and valine), may improve exercise performance and recovery from exercise.
Protein intake recommendations
The RDA for protein in healthy adults is 0.8 g/kg body weight per day. This number does not take into consideration protein quality, energy intake, carbohydrate intake, mode and intensity of exercise, or the timing of the protein intake. Based on current research, which takes into consideration the above, more appropriate levels have been recommended depending on the type of exercise.
Recommended protein intake for endurance exercise ranges from of 1.0 g/kg to 1.6 g/kg per day depending on the intensity and duration of the endurance exercise, as well as the training status of the individual. Recommendations for strength/power exercise typically range from 1.6 to 2.0 g/kg/day. For athletes involved in exercise activities that are intermittent in nature (e.g., soccer, basketball etc.) the recommended protein intake is 1.4–1.7 g/kg.
Protein intake above the RDA and safety concerns
There are some reports that chronically high protein intake above the RDA is unhealthy and may result in unnecessary metabolic strain on the kidneys, leading to impaired renal function. Another concern is that high protein diets increase the excretion of calcium, thereby increasing the risk for osteoporosis.
Both of these concerns are unfounded as there is no substantive evidence that protein intakes in the ranges suggested above, in conjunction with a balanced diet, will have adverse effects in healthy, exercising individuals.
(Pecoits-Filho, 2007) (Kerstetter, 2005)
Protein quality and common types of protein supplements
Protein can be found in both animal (e.g., eggs, dairy, meat, and fish) and plant sources (e.g., grains, legumes, soy, nuts/seeds and vegetables).
In general, animal sources provide a more complete amino acid profile as they have all the essential amino acids. Soy and quinoa are plant sources that are considered complete proteins.
Two of the most popular types of protein supplements are whey and casein. Whey protein induces a faster increase of plasma amino acids following ingestion, making it a better choice immediately following exercise, whereas casein induces a moderate, prolonged increase in plasma amino acids, making it a better choice as part of an evening smoothie.
For those who are vegetarian, there are a number of protein powder supplement options, such as soy, rice, pea, and hemp. Some of these have been shown to have comparable effects to whey protein supplements on body composition and performance.
Active individuals require more dietary protein due to an increase in protein oxidation and protein breakdown, as well as additional protein resynthesis within the muscles. Consequently, a strategically planned protein intake around exercise is essential for preserving muscle mass, eliciting muscular hypertrophy, ensuring proper recovery from exercise, and sustaining optimal immune function.
(Esmarck, 2001) (Volek, 2004)
Since whey protein elicits immuno-enhancing properties, ingesting this form of protein immediately before and following exercise training is beneficial for increasing muscle mass, recovery following exercise, and sustaining immune function during high-volume training periods.
Due to the effect of carbohydrates on insulin, the concomitant ingestion of protein and carbohydrates prior to and/or following exercise would be an effective synergistic combination for increasing muscle protein synthesis.
Branched Chain Amino Acids (BCAA) and exercise
The branched-chain amino acids (i.e. leucine, isoleucine and valine) constitute approximately one-third of skeletal muscle protein,with leucine playing the most significant role in stimulating muscle protein synthesis.
Amino acid supplementation (particularly the BCAAs) may be advantageous for the exercising individual; however, an attempt should be made to obtain all recommended BCAAs from whole food protein sources, such as red meat, dairy, chicken, fish, and eggs. Whey protein and egg protein supplements are also good options.
- Exercising individuals need more dietary protein than sedentary individuals, with the needs approximately 1.4 to 2.0 grams of protein per kilogram of bodyweight per day.
- Ultimately, the amount is dependent upon the mode and intensity of the exercise, the quality of the protein ingested, and the status of the energy and carbohydrate intake of the individual.
- Concerns that protein intake within this range is unhealthy are unfounded in healthy, exercising individuals.
- Ideally, protein requirements should come from whole foods, but supplemental protein, such as whey and casein, are safe and convenient options.
- Eating protein before, during and after a workout can lead to improved recovery and greater gains in lean body mass.
- Branched chain amino acids have been shown to increase the rates of protein synthesis, decrease the rate of protein degradation, and possibly aid in the recovery from exercise.
Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrere B: Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A 1997, 94(26):14930-14935.
Bounous G, Batist G, Gold P: Immunoenhancing property of dietary whey protein in mice: role of glutathione. Clin Invest Med 1989, 12(3):154-161.
Campbell, B, Kreider, R, Ziegenfuss, T, Bounty, P, Roberts, M, Burke, D, Landis, J, Hector Lopez, H and Antonio, J. International Society of Sports Nutrition position stand: protein and exercise. Journal of the International Society of Sports Nutrition 2007, 4:8.
Esmarck B, Andersen JL, Olsen S, Richter EA, Mizuno M, Kjaer M: Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. J Physiol 2001, 535(Pt 1):301-311.
Joy, J, Lowery, R, Wilson, J, Purpura, M, De Souza, E, Wilson, S. Kalman, D, Dudeck, J, Ralf Jäger, R. The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance. Nutrition Journal 2013, 12:86.
Kerstetter JE, O'Brien KO, Caseria DM, Wall DE, Insogna KL: The impact of dietary protein on calcium absorption and kinetic measures of bone turnover in women. J Clin Endocrinol Metab 2005, 90(1):26-31.
Lemon PW. Beyond the zone: protein needs of active individuals. J Am Coll Nutr 2000, 19(5 Suppl):513S-521S.
Pecoits-Filho R: Dietary protein intake and kidney disease in Western diet. Contrib Nephrol 2007, 155:102-112.
Rennie MJ, Bohe J, Smith K, Wackerhage H, Greenhaff P: Branched-chain amino acids as fuels and anabolic signals in human muscle. J Nutr 2006, 136(1 Suppl):264S-8S.
Roberts S, Desbrow B, Grant G, Anoopkumar-Dukie S, Leveritt M. Glycemic response to carbohydrate and the effects of exercise and protein.Nutrition. 2013 Jun;29(6):881-5.
Volek, J. Influence of Nutrition on Responses to Resistance Training: Med Sci Sports Exercise 36 no. 4 April 2004.