A study conducted by the International Society of Sports Nutrition reviewed the position stand of protein and exercise for trained individuals. The article outlined seven specific points relating to the intake of protein for healthy, exercising individuals. The Recommended Daily Allowance (RDA) of protein according to U.S. government standards is 0.8 gram per kilogram (2.2 pounds) of ideal body weight for the adult.
This protein RDA is specified to meet the majority of the populations protein needs. Since athletes and trained individuals have a higher demand for nutrients-particularly protein-it was necessary to reevaluate the current needs of this demographic.
The following points have been approved by the Research Committee of the Society.
- Vast research supports the contention that individuals engaged in regular exercise training require more dietary protein than sedentary individuals.
- Protein intakes of 1.4 - 2.0 g/kg/day for physically active individuals is not only safe, but may improve the training adaptations to exercise training.
- When part of a balanced, nutrient-dense diet, protein intakes at this level are not detrimental to kidney function or bone metabolism in healthy, active persons.
- While it is possible for physically active individuals to obtain their daily protein requirements through a varied, regular diet, supplemental protein in various forms are a practical way of ensuring adequate and quality protein intake for athletes.
- Different types and quality of protein can affect amino acid bioavailability following protein supplementation. The superiority of one protein type over another in terms of optimizing recovery and/or training adaptations remains to be convincingly demonstrated.
- Appropriately timed protein intake is an important component of an overall exercise training program, essential for proper recovery, immune function, and the growth and maintenance of lean body mass.
- Under certain circumstances, specific amino acid supplements, such as branched-chain amino acids (BCAAs), may improve exercise performance and recovery from exercise.
Protein Intake Recommendations
The RDA for healthy adults (0.8 g/kg body weight per day) was created to allow for an individual's differences in protein metabolism-since people's metabolic rate can vary due to numerous factors. That recommendation for protein intake covers that vast majority of society-approximately 97.5%- which may be adequate for non-exercising individuals. Since exercise breaks down additional foodstuffs coming from protein, carbohydrates and fats, trained individuals require more calories-especially coming from protein to accommodate recovery and muscle maintenance.
Most studies related to protein requirements use nitrogen balance assessments and amino acid tracer studies. This has one primary disadvantage for trained individuals because nitrogen balance studies may underestimate the amount of protein needed for optimal performance related to exercise. All athletes whether endurance, resistance, or any other form of training require additional protein to fuel their metabolism.
For endurance training individuals, recommended protein intakes range 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. Strength/power exercise is thought to increase protein requirements even more than endurance exercise, particularly during the initial stages of training and/or sharp increases in volume. Recommendations for strength/power exercise typically range from 1.6 to 2.0 g/kg/day.
Little research has been conducted on exercise activities that are intermittent in nature (e.g., soccer, basketball, mixed martial arts, etc.).
The position of the International Society of Sport Nutrition is that exercising individuals ingest protein ranging from 1.4 to 2.0 g/kg/day.
Endurance Exercise: Should ingest levels at the lower end of the Calculated range. Intermittent Activities: Should ingest levels in the middle of the Calculated range. Strength/Power Exercise: Should ingest levels at the upper end of the Calculated range.
Safety Of Protein Intakes Higher Than RDA
Within the media there has been widespread reports that high levels of protein intake puts heavy stress on the kidneys. There has been other reports indicating that high protein diets increase excretion of calcium-leading to an increased risk of osteoporosis. Both of these concerns have no scientific substantiation whatsoever. Most of the cited sources relate to studies done on animals and patients with co-exiting renal (kidney) disease. For healthy individuals-with no disease or impairment-higher levels of protein intake for exercising individuals are safe, and desired for optimal performance.
Protein Quality And Common Types Of Protein Supplements
To obtain supplemental dietary protein, exercising individuals often ingest protein powders. Powdered protein is convenient and, depending on the product, can be cost-efficient as well. Common sources of protein include milk, whey, casein, egg, and soy-based powders. Different protein sources and purification methods may affect the bioavailability of amino acids. Bioavailability can be best defined as how well your body breaks down and absorbs protein in the blood stream.
Commercially, the two most popular types of proteins in supplemental form are whey and casein. The differences in the digestibility and absorption of these protein types may indicate that the ingestion of "slow" (casein) and "fast" (whey) proteins differentially mediate whole body protein metabolism due to their digestive properties.
The recommendation of the International Society of Sport Nutrition is that individuals engaging in exercise attempt to obtain their protein requirements through whole foods. When supplements are ingested, we recommend that the protein contain both whey and casein components due to their high protein digestibility corrected amino acid score and ability to increase muscle protein accretion.
The Role Of BCAAs In Exercise
The branched-chain amino acids (i.e. leucine, isoleucine and valine) constitute approximately one-third of skeletal muscle protein. An increasing amount of literature suggests that of the three BCAAs, leucine appears to play the most significant role in stimulating protein synthesis. In this regard, amino acid supplementation (particularly the BCAAs) may be advantageous for the exercising individual.
BCAA ingestion has been shown to be beneficial during aerobic exercise. When BCAAs are taken during aerobic exercise the net rate of protein degradation has been shown to decrease . Equally important, BCAA administration given before and during exhaustive aerobic exercise to individuals with reduced muscle glycogen stores may also delay muscle glycogen depletion.
Because BCAAs have been shown to aid in recovery processes from exercise such as stimulating protein synthesis, aiding in glycogen resynthesis, as well as delaying the onset of fatigue and helping maintain mental function in aerobic-based exercise, we suggest consuming BCAAs (in addition to carbohydrates) before, during, and following an exercise bout. Any deficiency in BCAA intake from whole foods can easily be remedied by consuming whey protein during the time frame encompassing the exercise session; however, an attempt should be made to obtain all recommended BCAAs from whole food protein sources.
The position of the International Society of Sports Nutrition is that exercising individuals need approximately 1.4 to 2.0 grams of protein per kilogram of bodyweight per day. 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. An attempt should be made to obtain protein requirements from whole foods, but supplemental protein is a safe and convenient method of ingesting high quality dietary protein.
The timing of protein intake in the time period encompassing the exercise session has several benefits including improved recovery and greater gains in fat free mass. Protein residues such as branched chain amino acids have been shown to be beneficial for the exercising individual, including increasing the rates of protein synthesis, decreasing the rate of protein degradation, and possibly aiding in recovery from exercise. In summary, exercising individuals need more dietary protein than their sedentary counterparts, which can be obtained from whole foods as well as from high quality supplemental protein sources such as whey and casein protein.