Abstract-Prospective data on the associations between intake of dairy products and its nutrient components with risk of hypertension remain limited. We therefore investigated the associations of intake of dairy products, calcium, and vitamin D with the incidence of hypertension in a prospective cohort of 28 886 US women aged Ն45 years. Intake of dairy products, calcium, and vitamin D at baseline were assessed from semiquantitative food frequency questionnaires. Incident cases of hypertension (nϭ8710) were identified from annual follow-up questionnaires during 10 years of follow-up. After adjusting for major hypertension risk factors, the relative risks of incident hypertension across increasing quintiles of low-fat dairy product intake were 1.00 (reference), 0. Key Words: diet Ⅲ dairy products Ⅲ calcium Ⅲ vitamin D Ⅲ hypertension Ⅲ women Ⅲ population study P revious studies have suggested an inverse association of dairy product consumption with metabolic syndrome, 1 type 2 diabetes, 2 and cardiovascular disease. 3 These potential benefits of dairy consumption are usually attributed to major nutrients in dairy products such as calcium. High calcium intake decrease levels of parathyroid hormone and 1,25-(OH) 2 vitamin D and thus reduce calcium influx from outside the cell. 4 Reduced intracellular calcium may stimulate lipolysis and inhibit lipogenesis, 5 promote insulin-stimulated signal transduction, 4 and suppress vascular smooth muscle tone. 6 Because vitamin D is critical for calcium absorption and homeostasis, 7 the metabolism of these 2 nutrients are intimately interrelated.Population studies on the associations between dairy product consumption and the incidence of hypertension or increase in blood pressure (BP) have been limited to children, 8 young adults, 1,9 and adults in Mediterranean countries, 10 with results generally suggesting an inverse association. The Dietary Approaches to Stop Hypertension (DASH) trial has demonstrated that a combined diet rich in fruits, vegetables, and low-fat dairy products and low in total and saturated fat effectively reduced BP in subjects with and without hypertension, and the BP lowering effects of the combined diet with emphasis on dairy consumption were more profound compared with a diet rich in fruits and vegetables alone. 11 To provide further evidence on the potential role of dairy consumption in prevention of hypertension, we examined the prospective associations between intake of dairy products, from both high-fat and low-fat food sources, as well as the major nutrient components in dairy products, calcium and vitamin D, with the risk of hypertension in a large cohort of middle-aged and older US women.
Methods
Study PopulationThe Women's Health Study (WHS) was a randomized, double-blind, placebo-controlled, 2ϫ2 factorial trial evaluating the risks and benefits of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer. 12 A third component, -carotene, was initially included in the trial but terminated after a median treatme...