New insights into protein intake and progression of renal disease

PURPOSE OF REVIEWFor several decades, dietary protein restriction has been considered as a strategy to slow renal disease progression. Recently, a National Kidney Foundation advisory board incorporated recommendations for supervised low-protein diets into guidelines for the care of non-dialyzed patients with chronic kidney failure. Despite this consensus statement, the clinical utility of dietary modification remains controversial. This article reviews new investigations of protein intake as a mediator of renal function and physiology published since 1 October 2002. RECENT FINDINGSPopulation-level data indicate graded risk for progressive renal functional decline with increasing protein intake among women with mild renal insufficiency, and support a possible association of higher protein consumption with the risk of microalbuminaruia in people with concomitant diabetes and hypertension. A link between the quantity of protein intake and the rate of renal deterioration is suggested by preliminary prospective studies among incident peritoneal dialysis patients, renal transplant recipients, and animal models of kidney disease. Varied renal consequences based on protein composition were reported in population-based studies, animal-model experiments, and animal studies of in-utero protein exposure. Clinical trial experience raises concern for the feasibility of dietary interventions in practice. SUMMARYNew research supports the view that high-protein diets accelerate renal disease progression, suggests differential consequences based on protein source, and explores risk among defined sub-populations. Topics for future exploration include the renal impact of high-protein weight-loss regimens, implications of dietary protein quantity and type across the stages of chronic kidney disease, and translation of animal studies of prenatal nutrition to humans.