Impact of Dairy Consumption on Hypertension: a Clinical Study

Hypertension and endothelial dysfunction are being increasingly recognized as key etiological factors in the development of atherosclerosis and subsequent cardiovascular disease (CVD). A substantial body of evidence indicates that treating patients with elevated blood pressure (BP) leads to marked reduction in the risk of stroke, myocardial infarction, heart failure, and renal failure. There is also accumulating evidence associating endothelial dysfunction, which is defined as incapacity of the arteries to vasodilate when required, to elevated BP and an increased risk of CVD.

While there are more and more studies on how diet affects BP in healthy subjects, the impact of dairy consumption per se on both endothelial function and ambulatory BP has not been well characterized in patients with established essential hypertension. Therefore, the general objective of the study is to investigate in a single-blind randomized controlled study the impact of dairy consumption on ambulatory BP and endothelial function in subjects with mild to moderate essential hypertension.

The proposed research will be undertaken as a single-center randomized cross-over controlled study. A total of 80 men and women with mild to moderate essential hypertension but otherwise healthy will consume two 4-week diets, one rich in dairy and one without dairy, while consuming a diet low in saturated fat (\<10% energy), in trans fat (\<1% energy) and in cholesterol (\<200 mg/day). During the DAIRY diet, subjects will be asked to incorporate 3 servings of dairy (milk, yogurt, cheese) into their every day diet. During the CONTROL arm of the study, participants will be asked to consume energy equivalent replacement products. The primary analysis consists in comparing mean daytime ambulatory BP values and endothelial function between the two treatments.

A 2-week stabilization run-in period will precede the randomization of participants. During this run-in period, participants will be asked and instructed to adapt their diet to a prudent dietary pattern low in saturated fat (\<10% energy), in trans fat (\<1% energy) and in cholesterol (\<200 mg/day). The total amount of fat in the diet will not be restricted, with recommendations ranging from 25-35% of energy. However, substitution of saturated for unsaturated fat will be advocated. Sodium intake \<2300 mg/d will also be recommended. Recommendations will also include advice on how to restrict the consumption of processed and energy dense foods. This 2-week run-in period will allow participants to familiarize themselves with the dietary recommendations used during the intervention per se. The two diets will be separated by a 4-week wash out period and will also consist to the prudent dietary pattern recommended. It must be stressed that foods will not be provided during the run-in and wash-out periods. These periods are imposed to minimize the inter- and intra-individual variability before and between the experimental phases.

Eligibility Criteria:
Inclusion Criteria:

* Men and women aged between 18 and 70 years
* Mean daytime systolic blood pressure ≥ 135 mm Hg and ≤ 160 mm Hg
* Mean daytime diastolic blood pressure ≤ 110 mm Hg
* Consumption of dairy products fewer than 2 servings per day

Exclusion Criteria:

* Mean daytime systolic blood pressure \> 160 mm Hg
* Mean daytime diastolic blood pressure \> 110 mm Hg
* Dairy intake \> 2 serving per day
* Smokers (\>1 cigarette/day)
* Body weight variation \>10% during the last 6 months prior to the study baseline
* BMI \>35 kg/m2
* Previous history of cardiovascular disease, type 2 diabetes and monogenic dyslipidemia
* Subject taking anti-inflammatory drugs
* Subject with endocrine or gastrointestinal disorders
* Allergy, intolerance or aversion to dairy
* Clinical use of vitamin D or calcium supplements
* Vegetarians