Association of Intake of Whole Grains with Health Outcomes in the Chronic Renal Insufficiency Cohort Study.

Abstract

Patients with chronic kidney disease (CKD) are encouraged to choose refined grains instead of whole grains as part of the low-phosphorus diet for managing chronic kidney disease-mineral and bone disorders (CKD-MBD). However, there is no direct evidence indicating that limiting whole grains has a beneficial impact on CKD outcomes. This study analyzed Chronic Renal Insufficiency Cohort data in two ways, namely cross-sectional examination of CKD-MBD biomarkers and prospective examination of health outcomes. A total of 4,067 (cross-sectional) and 4,331 (prospective) participants were included. The primary exposure was reported intake of whole grains (analyzed as servings/day, servings/1,000kcal, and refined grain servings/whole grain servings). CKD-MBD biomarkers included serum phosphorus, fibroblast growth factor-23, parathyroid hormone, calcitriol, and calcium. Outcomes included cardiovascular events, kidney failure, and all-cause mortality. In adjusted models, reported intake of whole grains was associated with higher phosphorus intake and serum phosphorus when assessed crudely (serving/day), but not when analyzed in relation to energy. Higher intake of refined grain relative to whole grains was associated (all models) with higher risk of kidney failure (Model 4: 1.01, 95% CI 1.00 to 1.02; P=0.01, all-cause mortality (Model 4: 1.01, 95% CI 1.00 to 1.01; P=0.01), and cardiovasulcar disease except for the fully adjusted model. Higher dietary density was associated with lower mortality in models adjusted for demographic and clinical factors including kidney function, but not in the fully adjusted model that futher adjusted for dietary factors. Intake of whole grains was not associated with CKD-MBD biomarkers. Intake of whole grains in relation to refined grains was associated with lower risk of cardiovascular disease, kidney failure, and mortality. The results of this study put into question the long-standing practice of restricting whole grains in patients with chronic kidney disease.