Dietary calcium, vitamin D, and the prevalence of metabolic syndrome in middle-aged and older US women

OBJECTIVE - To examine whether and to what extent intakes of calcium and vitamin D are related to the metabolic syndrome in middle-aged or older women. RESEARCH DESIGN AND METHODS - We analyzed data from 10,066 women aged >= 45 years participating in the Women's Health Study who were free of cardiovascular disease, cancer, or diabetes and who never used postmenopausal hormones. We used multiple logistic regression models to estimate multivariable odds ratios (ORs) and 95% CIs comparing different dietary intake levels of calcium and vitamin D. RESULTS - in age- and calorie-adjusted analyses, higher intakes of total, dietary, and supplemental calcium were significantly and inversely associated with the prevalence of metabolic syndrome. After further adjusting for smoking status, exercise, alcohol intake, multivitamin use, and parental history of myocardial infarction before age 60 years, the ORs of having the metabolic syndrome for increasing quintiles of total calcium intake were 1.00 (reference), 0.82 (95% CI 0.70-0.97), 0.84 (0.71-0.99), 0.70 (0.59-0.83), and 0.64 (0.54-0.77) (P for trend <0.0001). This association was not appreciably altered by additional adjustment for other dietary factors or total vitamin D intake. In contrast, neither total (P for trend = 0.13) nor supplemental (P for trend = 0.45) vitamin D was significantly associated with metabolic syndrome. Dietary Vitamin D was inversely associated with prevalence of metabolic syndrome but was not independent of total calcium intake. Similar strong relations between intakes of dairy products and metabolic syndrome were also observed. After adjustment for lifestyle and dietary factors, the multivariable ORs comparing highest with lowest intake categories were 0.66 (0.55-0.80) (P for trend <0.0001) for total dairy products and 0.85 (0.71-1.02) (P for trend = 0.05) for total milk intake. CONCLUSIONS - Our results indicate that intakes of calcium and dairy products may be associated with lower prevalence of the metabolic syndrome in middle-aged and older women.