Interaction between Vitamin D Status and Calcium Intake in Association with Blood Pressure and Hypertension

Abstract

Vitamin D deficiency and inadequate calcium intake are supposed to be poten-tially related to cardiovascular outcomes, however, their combined association with hypertension remains unclear. In this cross-sectional study among 2,352 subjects, dietary calcium intake was assessed by using a valid food frequency questionnaire, and serum 25-hydroxyvitamin D (25OHD) was measured by the Ultra Performance Liquid Chromatog-raphy system. Hypertension was defined as a level of systolic pressure $140 mmHg or diastolic pressure $90 mmHg, or both, or administration of antihypertensive medications. Vitamin D status was classified into deficiency (25OHD,20 ng/mL), insufficiency (20 ng/ mL#25OHD,30 ng/mL) and sufficiency (25OHD$30 ng/mL), while dietary calcium intake was divided into tertiles as low, medium, and high. Two-way analysis of variance (ANOVA) and multivariable logistic regression models were adopted. A significant interaction between vitamin D status and dietary calcium intake in relations to systolic blood pressure (p50.042) and hypertension (p50.029) indicates the associations of dietary calcium intake with systolic blood pressure and hypertension depend on the vitamin D status, and vice versa. Only in the vitamin D deficiency group, dietary calcium intake was significantly associated with systolic blood pressure level (b520.162, p,0.001) and prevalence of hypertension (odd ratio52.20, p,0.001). The significance was not substantially compro-mised after further adjustment for confounding factors. In conclusion, the combination of vitamin D deficiency and low dietary calcium intake, rather than alone, is associated with hypertension.