W E Mitch1. 1. Renal Division, Emory University School of Medicine, Atlanta, Georgia 30322, USA. wmitch@emory.edu
Abstract
BACKGROUND: In rats with experimental chronic renal failure (CRF), low-protein diets protect against histologic damage and improve mortality. In CRF patients, low-protein diets ameliorate uremic symptoms and certain CRF complications. Fortunately, low-protein diets are nutritionally sound in CRF patients because they activate compensatory mechanisms that conserve protein with a low-protein diet. These results do not determine if dietary protein restriction can slow the rate of progression of CRF or the time to dialysis. METHODS: Reports evaluating low-protein diets and changes in nutritional status and/or progression of CRF are analyzed for efficacy. The MDRD Study is reviewed in depth. RESULTS: When dietary compliance was achieved, the nutritional status was unimpaired and progression was slowed. Studies with limited dietary compliance failed to find any beneficial effect on progression. Problems in study design suggest caution before accepting the initial MDRD Study conclusion that dietary restriction does not slow progression. Subsequent analyses of MDRD results indicate that protein restriction can slow progression of CRF. CONCLUSION: Evidence that dietary protein spontaneously decreases in progressively uremic patients should not be construed as an argument against the use of dietary therapy. Rather, it is a persuasive argument to restrict dietary protein intake in order to minimize CRF complications while preserving nutritional status. In patients with uremia or progression despite other measures, dietary therapy should be started along with monitoring for dietary compliance and nutritional adequacy.
BACKGROUND: In rats with experimental chronic renal failure (CRF), low-protein diets protect against histologic damage and improve mortality. In CRF patients, low-protein diets ameliorate uremic symptoms and certain CRF complications. Fortunately, low-protein diets are nutritionally sound in CRF patients because they activate compensatory mechanisms that conserve protein with a low-protein diet. These results do not determine if dietary protein restriction can slow the rate of progression of CRF or the time to dialysis. METHODS: Reports evaluating low-protein diets and changes in nutritional status and/or progression of CRF are analyzed for efficacy. The MDRD Study is reviewed in depth. RESULTS: When dietary compliance was achieved, the nutritional status was unimpaired and progression was slowed. Studies with limited dietary compliance failed to find any beneficial effect on progression. Problems in study design suggest caution before accepting the initial MDRD Study conclusion that dietary restriction does not slow progression. Subsequent analyses of MDRD results indicate that protein restriction can slow progression of CRF. CONCLUSION: Evidence that dietary protein spontaneously decreases in progressively uremicpatients should not be construed as an argument against the use of dietary therapy. Rather, it is a persuasive argument to restrict dietary protein intake in order to minimize CRF complications while preserving nutritional status. In patients with uremia or progression despite other measures, dietary therapy should be started along with monitoring for dietary compliance and nutritional adequacy.