There exists controversy between scientific literature and popular opinion regarding protein requirements for athletes (Phillips, Moore, & Tang, 2007). Some authorities recommend 0.8g/kg of bodyweight while others recommend as high as 1.7g/kg of bodyweight (Phillips et al., 2007). As a means of reconciling the aforementioned disparity, the following sections will explore the effects of ingesting protein above the recommended dietary allowances (RDAs), and its relationship to health and performance outcomes in athletic populations.
Dietary reference intakes (DRIs) are considered a permutation of Canadian recommended nutrient intakes and U.S. RDAs. DRIs now include an estimated average requirement (EAR), an RDA, and a tolerable upper limit (UL), which marks the point where adverse effects from higher nutrient intakes begin to appear (Phillips et al., 2007). Phillips et al. (2007) also provided a chart, which outlined the acceptable macronutrient distribution ranges (AMDRs) formulated by the Institute of Medicine (IOM).
The AMDR attempts to provide a template to “fit” a person to a macronutrient ratio considered sufficient to improving health. With respect to protein requirements, the range is 10-35% of total daily caloric consumption (Phillips et al., 2007). It should be noted, however, that all of the aforementioned information and data is predicated on preventing chronic disease and illness, not performance enhancement. Additionally, the percentages of protein were calculated after determining carbohydrate and fat consumption, indicating that an AMDR for total protein could not truly be established (Phillips et al., 2007). Thus, implementing a nutritional plan whose primary purpose is prevention of deficiency may not be an adequate or appropriate protocol to reach and fulfill athletes’ needs.
Phillips et al. (2007) argued that protein requirements for athletes must be based on improving the following athletic goals: repairing damaged proteins, remodeling proteins such as muscle, tendon, bone and ligaments, optimizing metabolic pathways, supporting increments in lean mass, optimizing immune function, and providing optimal plasma protein production. Considering the logic of Phillips et al. (2007), it would seem that RDAs for the sedentary population, and their goals of disease prevention, are not matched to the goals of most athletes. Of particular interest is that there is no known UL for protein consumption (Phillips et al., 2007).
Thus, it remains unclear if protein consumption above the RDA or UL has deleterious effects. Evidence by Phillips et al. (2007) indicated that strength and power athletes, as well as bodybuilders, consumed protein between 2-3g/kg of bodyweight per day with no apparent health effects. Additionally, Northern Canadian and Inuit peoples have been known to consume unusually high protein intakes throughout their entire lives without reports of ill health (Phillips et al., 2007). Thus, it would seem that protein consumption above the UL appears to have no known side effects in healthy populations.
Phillips et al. (2007) provided additional evidence, which supported benefits of higher daily protein consumption; in several studies, the higher the protein intake, the higher the peak bone mass was recorded to be. Other studies indicated that higher protein intake and reduced carbohydrate intake helped improve fat free mass (Phillips et al., 2007). Finally, controversy existed that increased UL protein intake would disrupt renal function, and Phillips et al. (2007) noted that such serious side effects were recorded in patients with pre-existing renal dysfunctions. However, the same side effects could not be conclusively applied to individuals with normal kidney function (Phillips et al., 2007). Having considered the positive effects of UL protein consumption, the following will explore if supplementation is a requirement and/or necessary.
UL protein consumption (i.e., above 1.7g/kg bodyweight) is possible to achieve without the requirement of additional supplementation. For example, a 170 lb male’s protein UL would be at least 129 g protein/day (170 lbs ÷ 2.25 kg) x 1.7 g/kg bodyweight). If the athlete ate four times a day (i.e., approximately 33 g protein/meal) meeting requirements could be achieved. However, there remains one caveat; immediately after intense exercise (i.e., heavy resistance exercise) the body is highly sensitive to protein consumption, offering a “window” that allows maximal absorption and usage of amino acids from protein (Phillips et al., 2007). The authors based their research on protein supplementation, however, and not through whole foods (Phillips et al., 2007). Thus, it may be equally possible to achieve the same effects through consumption of animal meats, eggs, dairy etc. However, an argument could be made that protein supplementation may provide convenience and ease of use.
Evidence suggests that protein consumption above ULs does not necessarily have deleterious effects on human health and performance. Indeed, Phillips et al. (2007) provided several examples, covered in previous sections, that higher protein consumption could improve biomarkers and performance tests, especially during endurance and strength-based exercise/sports. In conclusion, slightly higher ULs of protein may have a relevant place in athletic populations, that when applied judiciously, better matches nutritional plans to the athletes’ needs.
References
Phillips, S.M., Moore, D.R., & Tang, J.E. (2007). A critical examination of dietary protein requirements, benefits, and excesses in athletes. International Journal of Sport Nutrition and Exercise Metabolism, 17, 58-76.
-Michael McIsaac