Protein and Kidney Function
By Jamie Hale
How many times have you heard too much protein will destroy your kidneys. This is a common statement heard when speaking of high protein diets. You would think there should be mounds of evidence indicating this. After all: my doctor or dieteiatan said so. Like many other statements concerning nutrition the above statement cannot be verified by scientific or practical study. I have known hundreds of people who consume 300-400 gms of protein a day. Guess what, no kidney problems. I have searched through a multitude of studies and spoke to numerous coaches and nutrition consultants around the world and the resounding conclusion has been the same. There is no evidence what so ever of protein intake causing kidney damage in individuals with normal renal functioning.
Below is some highlights from a paper taking an in depth look at Protein and it’s effects on Kidney Function.
Dietary protein intake and renal function William F Martin* 1 , Lawrence E Armstrong* Nancy R, Rodriguez
Dietary protein intake can modulate renal function and its role in renal disease has spawned an ongoing debate in the literature. At the center of the controversy is the concern that habitual consumption of dietary protein in excess of recommended amounts promotes chronic renal disease through increased glomerular pressure and hyperfiltration . Media releases often conclude that, "too much protein stresses the kidney" . The real question, however, is whether research in healthy individuals supports this notion.
The purpose of this paper is to review the available evidence regarding the effects of protein intake on renal function with particular emphasis on renal disease. This review will consider research regarding the role of dietary protein in chronic kidney disease, normal renal function and kidney stone formation and evaluate the collective body of literature to ascertain whether habitual consumption of dietary protein in excess of what is recommended warrants a health concern in terms of the initiation and promotion of renal disease.
Chronic Kidney Disease (CKD) is defined as either kidney damage or a decline in renal function as determined by decreased glomerular filtration rate (GFR) for three or more months . It is estimated that 1 in 9 adults in the United States meet this criteria, while an additional 1 in 9 adults are at increased risk for CKD. In the general population, a decline in renal function is considered an independent risk factor for both cardiovascular disease and all-cause mortality.
The relationship between dietary protein and renal function has been studied for over half a century . In 1923, Addis and Drury were among the first to observe a relationship between level of dietary protein and rates of urea excretion. Soon after, it was established that increased protein intake elevated rates of creatinine and urea excretion in the dog model. The common mechanism underlying increased excretion rates was eventually attributed to changes in GFR and Van Slyke et al. demonstrated that renal blood flow was the basis for GFR mediated changes in clearance rates in response to increased protein intake. Clearly dietary protein effects GFR , with both acute and chronic increases in protein consumption elevating GFR.
Observational data from epidemiological studies provide evidence that dietary protein intake may be related to the progression of renal disease. In the Nurses' Health Study, protein intake, assessed with a semi-quantitative food frequency questionnaire, was compared to the change in estimated GFR over an 11-year span in individuals with pre-existing renal disease. Regression analysis showed an association between increased consumption of animal protein and a decline in renal function suggesting that high total protein intake may accelerate renal disease leading to a progressive loss of renal capacity. However, no association between protein intake and change in GFR was found in a different cohort of 1,135 women with normal renal function . The latter finding led the authors to conclude that there were no adverse effects of high protein intakes on kidney function in healthy women with normal renal status.
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