Abstract P389: Effects of Dietary Patterns on Vitamin D and Other Markers of Bone-Mineral Metabolism: Results From the Dash Trial

Abstract

Background: The relationship of CVD with vitamin D levels and other markers of bone-mineral metabolism is of substantial interest. The Dietary Approaches to Stop Hypertension (DASH) diet effectively lowers blood pressure and is now recommended to promote CV health. The effects of the DASH diet on vitamin D and other markers of bone-mineral metabolism is unknown. Objective: To determine the effect of dietary patterns on blood levels of vitamin D, PTH, and ionized calcium, and urinary excretion of calcium and phosphate. Methods: Data on study outcomes were available in 334 participants from the original DASH trial. Baseline levels were obtained from blood and urine collected at the end of the run-in while on the control diet. Participants were then randomized to control diet (37% kcal total fat); fruits & vegetable diet (also 37% kcal total fat); or the DASH diet (27% kcal total fat). Follow-up levels were obtained during the last week of the eight-week intervention period. Results: Mean (±SD) baseline blood levels of vitamin D, PTH , and ionized calcium were 15.1±3.7ng/ml, 46.1±18.5 ng/ml and 1.3±0.06 mmol/l, respectively. For urinary calcium and phosphate were 126.8±45.3mg/dl and 715.0±277.3 mg/dl, respectively. See table for within-diet changes. The DASH diet, net of control, reduced vitamin D by -1.29ng/ml (P= 0.005). In stratified analyses, the reduction in vitamin D appeared more prominent in blacks, but the p-value for interaction (race*diet) was non-significant (P=0.21). Otherwise, the DASH diet had no significant effect on the other markers, net of control. Compared to control, the fruit & vegetable diet reduced urinary calcium and phosphorus excretion. Conclusion: The DASH diet modestly reduced vitamin D levels among all participants, with potentially larger effects in blacks. The reduction in vitamin D levels might have resulted from the lower fat content of the DASH diet. Overall, during the eight-weeks of intervention, no major harm or benefit of the DASH diet was documented on biomarkers related to bone-mineral metabolism.