Many people including researchers have different opinions when it comes to the amount of protein your body needs on a daily basis when involved with consistent exercise. Do you need the suggested RDA of 0.8 grams/kg/day or is it more in line with 1-2 gram/kg/day? The answer may depend partly on the volume of daily exercise you’re doing, if you’re a strength or an endurance athlete, your age etc. Here is what some of the research has shown. Back in the 1970’s and early 1980’s, a few published studies suggested exercise might actually cause significant changes in protein metabolism (1).
One study done at the USDA HNRC on Aging at Tufts University in 1988 (in which I was a test subject) by Meredith and colleagues looked at the protein needs of six young (26.8 +/- 1.2 yr) and six middle-aged (52.0 +/- 1.9 yr) endurance-trained men. All subjects consumed either 0.6, 0.9, or 1.2 grams/kg/day of high-quality protein over three separate 10-day periods, while maintaining training and constant body weight. The results of the study estimated that protein requirement was 0.94 +/- 0.05 grams/kg/day for the 12 men, with no effect of age. The data demonstrated that endurance exercise was associated with dietary protein needs greater than the current Recommended Dietary Allowance of 0.8 g/kg/day. Several studies (2, 3) based on data that were collected on individuals who were engaged in regular aerobic exercise, that was more vigorous in nature, demonstrated a higher protein need more in line with 1.1 to 1.4 grams/kg/day. This by the way is about 38%-75% above the current RDA range. In regard to strength training, there is good evidence that the current recommended protein intake will actually limit muscle growth (4). Some researcher’s report an optimal intake more in line with a protein range of 1.5 to 1.8 grams/kg/day (4,5) that is 88% to 125% above RDA.
Dietary protein needs according to Lemon et al. (1) of physically active individuals have been debated for centuries. It does not seem the RDA guidelines are going to change any time soon. If you are involved in vigorous, physical activity such as strength training on a regular basis, there is evidence to support the need for higher protein intake more in line with 1.1 to 1.5 grams/kg/day in order to effectively build lean muscle tissue (1-5). If you are not involved in regular exercise, the RDA of 0.8 grams/kg/day will suffice.
1. Lemon, PWR (2000). Protein metabolism during exercise. Exercise and Sport Science, 19-27.
2. Evans WJ et al. (1983). Protein metabolism and endurance exercise Phys Sports Med 11:63-72.
3. Friedman JE et al. (1989). Effect of chronic endurance exercise on the retention of dietary protein. Int J Sports Med 10:118-123.
4. Tarnoplosky MA (1992) et al. Evaluation of protein requirements for trained strength athletes. J Applied Physiology 73:1986-1995.
5. Lemon PWR, Tarnoplosky MA et al. (1992). Protein requirements and muscle mass/strength changes during intensive training in novice bodybuilders. J Applied Physiology 73:767-775.