Dietary protein safety and resistance exercise: what do we really know?

There appears to be an element of disconnectedness between scientific evidence and health messages offered to students and athletes. Statements of concern over the effects of ample dietary protein intakes appear in Table 1. Research on healthy populations, however, does not support such concerns. One summary of the literature on this topic, the International Society of Sports Nutrition (ISSN) Position Stand: Protein and Exercise [1] reviewed literature on renal and bone health, among other topics. Although balanced in its inclusion of both negative (no evidence of harm) and positive (extrapolated evidence of potential concern) studies, the position stand was largely without mention of athlete-specific data on safety topics. Examples of athlete-specific research, although rare, do exist and are included in this review. Three safety issues are commonly mentioned in popular media and nutrition and dietetic textbooks, while sports governing bodies may focus upon the risk of dietary supplements per se [2,3]. One issue is renal "stress", [2,4] a second issue is calcium loss and bone catabolism [2,5,6] and a third is an assumption that higher protein intakes are higher in saturated fat and lower in fiber [2]. Language surrounding these topics can be dissuasive and/or uncertain regarding purposeful consumption of protein for weight control or athletic reasons. (Table 1.) Although difficult to document due to its frequently verbal nature, this is a curious phenomenon considering the lack of evidence, particularly among strength athletes, who are widely known to pursue additional dietary protein for performance or body composition purposes [7].It is important to point out that quotes listed in Table 1 are not necessarily incorrect and may be followed or preceded by qualifying language. The statements do reflect an element of dissuasion (considering that overconsumption or excess of any nutrient is unhelpful or risky) and/or uncertainty (considering that studies present confli