Dietary plant and animal protein intake and decline in estimated glomerular filtration rate among elderly women: a 10-year longitudinal cohort study

Background. Many older women demonstrate an age-related accelerating rate of renal decline that is associated with increased rates of bone disease, cardiovascular disease and mortality. Population-based protein restriction has been studied principally in patients with reduced renal function. In this investigation, we examined the hypothesis of a differential effect of plant-derived protein compared with animal-derived protein on renal function in older women. Methods. We assessed dietary intake from a validated food frequency questionnaire and the estimated glomerular filtration rate (eGFR) (using the Chronic Kidney Disease Epidemiology Collaboration creatinine and cystatin C equation) at baseline, 5 and 10years in the Longitudinal Study of Aging Women cohort. We tested the association between plant- and animal-sourced protein intake and kidney function using linear mixed modeling. Results. A total of 1374 Caucasian women [mean (standard deviation, SD) age=75years (2.7) and mean (SD) baseline eGFR=65.6mL/min/1.73m(2) (13.1)] contributed to the analysis. The average decline in eGFR was 0.64mL/min/1.73m(2)/year [95% confidence interval (CI) 0.56-0.72]. Higher intakes of plant-sourced protein were associated with slower declines in eGFR after adjusting for covariates including animal protein and energy intake (P=0.03). For each 10g of plant protein, the yearly decline in eGFR was reduced by 0.12mL/min/1.73m(2) (95% CI 0.01-0.23), principally associated with fruit-, vegetable- and nut-derived protein. The intake of animal protein was not associated with eGFR decline (P=0.84). Conclusions. Older women consuming a diet that is richer in plant-sourced protein have a slower decline in kidney function. These data extend support for the health benefits of plant-rich diets in the general population to maintain kidney health.