Dietary protein intake and change in estimated GFR in the Cardiovascular Health Study

Objective: With aging, kidney function declines, as evidenced by reduced glomerular filtration rate. It is controversial whether or not high protein intake accelerates this decline. The aim of this study was to determine whether high protein intake was associated with declines in kidney function among older patients. Methods: We examined whether dietary protein is associated with change in kidney function (mean follow-up 6.4 y [SD = 1.4, range = 2.5-7.9] in the Cardiovascular Health Study (N = 3623). We estimated protein intake using a food frequency questionnaire and estimated glomerular filtration rate from cystatin C. Associations between protein intake and kidney function were determined by linear and logistic regression models. Results: Average protein intake was 19% of energy intake (SD = 5%). Twenty-seven percent (n = 963) of study participants had rapid decline in kidney function, as defined by (δeGFR_cysC > 3 mL•min•1.73 m²). Protein intake (characterized as g/d and % energy/d), was not associated with change in estimated glomerular filtration rate (P > 0.05 for all comparisons). There were also no significant associations when protein intake was separated by source (animal and vegetable). Conclusion: These data suggest that higher protein intake does not have a major effect on kidney function decline among elderly men and women.