http://www.nytimes.com/2011/05/31/health/31really.html?_r=1&ref=science

Anyone who has tried a high-protein diet has probably heard this warning: You may lose weight, but you risk kidney damage.

The idea is that processing large amounts of protein strains your kidneys, which filter blood and remove waste. But there is little research backing that assertion.

In one study, in The International Journal of Sport Nutrition and Exercise Metabolism, researchers recruited bodybuilders and other athletes, then examined their kidney function over seven days as they followed high- and medium-protein diets. The researchers found that every marker of kidney function was within the normal range in all of the athletes who consumed large amounts of protein.

In a much larger study, published in The Annals of Internal Medicine, researchers looked at protein intake in 1,624 women over an 11-year period. They found that high-protein diets did not cause any problems in women with normal kidney function. But in women who had “mild renal insufficiency,” they wrote, consuming large amounts of protein accelerated renal decline. University of Connecticut researchers reached a similar conclusion when they reviewed years of research on the subject in a 2005 report in the journal Nutrition & Metabolism.