This is a follow-up to my blog post last week regarding protein requirements. Despite the common practice of consuming greater amounts of protein in strength training athletes, there is little data suggesting there is any benefit to doing this. The U.S. dietary supplement industry, which includes the protein supplementation industry, generates more than $30 billion annually.
Regarding protein requirements, the Estimated Average Requirement (EAR) is 4-5% total calories per day for adults. The EAR is expected to satisfy the needs of 50% of people in that age group. To figure out this threshold, scientists measured the protein consumption of different people and tracked them to see if they displayed any symptoms of protein deficiency and correlated these symptoms with the different amounts of protein people were consuming.
The U.S. Recommended Daily Allowance (RDA) is calculated based on the EAR, usually 20% higher than the EAR. The RDA meets the requirements of 97.5% of individuals in each life stage and sex group, implying that the intake level would cause a nutrient deficiency in just 2.5%. For protein, the RDA is 8-10% of calories or 0.8/mg/kg of body weight. For a 70 kg male, this would equate to 56 g/day.
To determine protein requirements for athletes, nitrogen balance studies have been used. This technique involves calculating the protein that enters the body and measuring the nitrogen excreted. Proteins are 16% nitrogen, and the body excretes nitrogenous compounds rather than whole protein. These studies have found that low to moderate intensity recreational endurance exercise does not require dietary protein in excess of the current RDA.
Studies have even shown that more intense resistance exercise can even improve nitrogen economy. In other words, exercising improves dietary protein retention. Unaccustomed endurance exercise may initially induce a negative nitrogen balance, but in one study, this improved within 12 days of exercise.
For the strength training athlete, a level of 1.33g/kg/day of protein is likely sufficient. Most people are already consuming enough protein to meet these needs. Dietary protein intake should generally not be a concern for athletes consuming 10-15% protein and getting adequate calories to meet the needs of their activity. According to the National Health and Nutrition Examination Survey (from data from 1999-2000), adults consumed an average of 15 percent of calories from protein. Since most people already get enough protein, there is no need for supplementation. From a Consumer Reports review from July 2010:
“Our Investigation, including tests at an outside laboratory of 15 protein drinks, a review of government documents, and interviews with health and fitness experts and consumers, found most people already get enough protein, and there are far better and cheaper ways to add more if it’s needed. Some protein drinks can even pose health risks, including exposure to potentially harmful heavy metals, if consumed frequently. All drinks in our tests had at least one sample containing one or more of the following contaminants: arsenic, cadmium, lead, and mercury…”
References
“Alert: Protein drinks: You don’t need the extra protein or the heavy metals our tests found.” Consumer Reports Magazine, 2010.
S.M. Pasiakos, S.J. Mountain, A.J. Young, “Protein Supplementation in U.S. Military Personnel.” The Journal of Nutrition, vol. 148, no. 11, pp.18155-18195, 2013.
S.M. Phillips, “Protein requirements and supplementation in strength sports.” Nutrition , vol. 20, issue 7-8 ,pp. 689-695, 2004.
M. Tarnopolsky, “Protein requirements for endurance athletes.” Nutrition, vol. 20, issue 7-8, pp. 662-668, 2004.