DIETARY-PROTEIN REQUIREMENTS IN ATHLETES

Current dietary protein requirements were determined using essentially sedentary individuals and, therefore, are designed for the general po pulation. Unfortunately, the recommendations from these studies have b een applied to athletes as well. Because of the vast differences in da ily energy expenditure alone this would seem to be a naive approach. M oreover in recent years, considerable evidence has accumulated on athl etes, primarily those involved at each end of the intensity-duration c ontinuum, i.e., strength (weight lifting) to endurance (running, cycli ng, or swimming), suggesting that dietary protein needs may be greater by as much as 125% in comparison to sedentary individuals. The additi onal protein may be necessary for use as an auxiliary fuel for enduran ce exercise and as a supplementary source of amino acids to build and/ or maintain the large muscle mass present in those who strength train. In addition, although more speculative, it is possible that other con stituents in high quality protein sources, i.e., creatine, conjugated linoleic acid, carnosine, etc. may also be beneficial. Definitive diet ary recommendations for various athletic populations must await furthe r study, but the mass of current evidence indicates that individuals i nvolved in strength/power/speed activities may benefit from intakes of about 1.7 to 1.8 g protein . g body mass(-1). day(-1) (approximately 112-125% higher than the sedentary recommendation) and those who parti cipate in endurance activities from about 1.2-1.4 g . kg(-1). d(-1) (a pproximately 50 to 75% higher than the sedentary recommendation). Assu ming total energy intake is sufficient to cover expenditure, these int akes can be obtained from a diet consisting of about 10% energy intake as protein. Some athletes may not consume this amount of protein, esp ecially those who consume inadequate energy (dieters or those trying t o maintain an arbitrary body mass for their activity, i.e., gymnasts, dancers, wrestlers, etc.), those who are growing (children, adolescent s, women who are pregnant), or those who select diets which may exclud e high quality protein sources (vegetarians and seniors). Despite the common practice of consuming greater amounts of protein (2-4 g . kg(-1 ). d(-1)) among strength athletes in particular, few data exist sugges ting that this has any further benefit, i.e., there appears to be a ce iling effect. Finally, the concerns expressed routinely about liver or kidney problems with high protein diets have little scientific suppor t; however, the easy accessibility of individual amino acid supplement s poses a potentially serious threat because there are likely a variet y of confounding interactions and the effects of mega doses of single amino acids are largely untested. Future studies are needed to fine tu ne these recommended. (C) Elsevier Science Inc. 1997.