Protein rich foods are one of the more basic ingredients in an athlete’s kitchen. Too often, people have been misinformed and misunderstand protein intake. How many times have others expressed concern for the amount of protein an athlete eats? In mainstream media, we are often told that a high protein diet will lead to kidney problems. As a strength athlete myself, I am used to hearing these claims, and was at first appalled by this. In the end, I decided to dig into the evidence and then bombard these concerned “health experts” with some cold hard research evidence.
Below we have part of the filtration system in a kidney. The kidneys are responsible for regulating fluid balance in the body. High protein intake, in this case 35% of total calories, increases the glomerular filtration rate. Supposedly, consuming excess amounts of protein increases filtration pressure in the kidneys, which is claimed to “strain” the kidneys and lead to renal damage.
A simplified look at glomerular filtration in the kidney.
This is an adaptation that is exactly comparable to getting stronger muscles as you lift heavier weights in the gym. Once you eat less protein, your kidneys will adapt and again slow the filtration rate. In healthy people and athletes, there is no evidence to support a “straining” of the kidneys. Strength athletes in particular have higher protein needs, especially during short periods of weight loss. Consuming more protein in the diet gives the body the building blocks it needs to rebuild and as preserves lean muscle mass.
In some research, different diets have been tested on various clinical populations. It was found that only in those who already had kidney issues was high protein intake an issue. Those who saw detriments to their kidney function with high protein foods, already has kidney diseases. Because a higher work rate is imposed on the kidneys, it makes sense that those with kidney pathologies do not do well on a high protein diet. The protein intake in research subjects did not cause the malfunction, rather diet in this population needs to match the lower work capacity of the kidneys. This does not leave athletes or those looking to lose weight in the clear to load up on protein. As always, quality sources are key and good lifestyle habits are also important. If you are not taking good care of your health and are training hard, you may be overloading your internal organs and putting yourself at risk for future pathologies.
Martin, W. F., Armstrong, L. E., & Rodriguez, N. R. (2005). Dietary protein intake and renal function. Nutrition & metabolism, 2(1), 25.
Mettler, S., Mitchell, N., & Tipton, K. D. (2010). Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc, 42(2), 326-37.