Thursday, April 28, 2011

EAT TO GROW : Bodybuilding-Diet Dangers? Does a high-protein intake lead to kidney damage? by Jerry Brainum

A frequent concern about high-protein diets is their effect on kidney function. On the surface that appears to make sense, since the liver and kidneys are the primary organs involved in protein metabolism and the excretion of waste products, such as urea. The latter function is handled mainly by the kidneys. The supposition is that a long-term high-protein diet eventually wears out and induces pathology in the kidneys.

The belief is rampant, often voiced even by those who should know better, such as medical professionals. Some allude to studies to prove their contention about the dangers of a high-protein diet. Perusal of such so-called proof, however, nearly always reveals that those adversely affected by a high-protein diet already had kidney disease. No study has ever shown that eating a high-protein diet leads to kidney problems in those with normal kidney function.

While it’s true that kidney function declines with age in many people, with older people showing an average of 40 percent kidney function, functional loss isn’t related to a high-protein diet; it’s most often related to a gradual loss of nephrons, the kidneys’ filtering units. That loss, in turn, is traceable to various health problems and drugs, such as long-term use of painkillers, including aspirin. Untreated high blood pressure is another primary cause of kidney-function loss, as is heart disease, due to poor blood circulation through the kidneys. Even healthy people can harm their kidneys through dehydration, which limits blood flow through the kidneys.

A recent study examined the effect of a high-protein diet in those engaged in regular weight training.1 It featured 77 men, average age 26, all of whom trained with weights. Their diets averaged 19 percent protein, which came out to 1.67 grams per kilogram of bodyweight daily, or 98 to 139 percent of the recommended intake for those engaged in weight training. Measurements of the three primary blood tests for kidney function—creatinine, blood urea nitrogen and uric acid—showed that all were within normal values. Thus, the study indicates that a high-protein intake doesn’t stress the kidneys in a normal weight-training population.

1 LaBounty, P., et al. (2005). Blood markers of kidney function and dietary protein intake of resistance trained males. J Int Soc Sports Nutr. 2:5.

©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.

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