Effects of low-fat dairy intake on blood pressure, endothelial function, and lipoprotein lipids in subjects with prehypertension or stage 1 hypertension

Abstract

Objective: This randomized crossover trial assessed the effects of 5 weeks of consuming low-fat dairy (one serving/day each of 1% fluid milk, low-fat cheese, and low-fat yogurt) versus nondairy products (one serving/day each of apple juice, pretzels, and cereal bar) on systolic and diastolic blood pressures (SBP and DBP), vascular function (reactive hyperemia index [RHI] and augmentation index), and plasma lipids.

Methods: Patients were 62 men and women (mean age 54.5 years, body mass index 29.2 kg/m(2)) with prehypertension or stage 1 hypertension (mean resting SBP/DBP 129.8 mmHg/80.8 mmHg) while not receiving antihypertensive medications. A standard breakfast meal challenge including two servings of study products was administered at the end of each treatment period.

Results: Dairy and nondairy treatments did not produce significantly different mean SBP or DBP in the resting postprandial state or from premeal to 3.5 hours postmeal (SBP, 126.3 mmHg versus 124.9 mmHg; DBP, 76.5 mmHg versus 75.7 mmHg), premeal (2.35 versus 2.20) or 2 hours postmeal (2.33 versus 2.30) RHI, and premeal (22.5 versus 23.8) or 2 hours postmeal (12.4 versus 13.2) augmentation index. Among subjects with endothelial dysfunction (RHI ≤ 1.67; n = 14) during the control treatment, premeal RHI was significantly higher in the dairy versus nondairy condition (2.32 versus 1.50, P = 0.002). Fasting lipoprotein lipid values were not significantly different between treatments overall, or in subgroup analyses.

Conclusion: No significant effects of consuming low-fat dairy products, compared with low-fat nondairy products, were observed for blood pressures, measures of vascular function, or lipid variables in the overall sample, but results from subgroup analyses were consistent with the hypothesis that dairy foods might improve RHI in those with endothelial dysfunction.

Keywords: blood pressure; dairy; endothelial function; hypertension; lipids.

Figure 1

Mean systolic (A) and diastolic (B) blood pressure values at time points throughout a meal challenge test and overall mean (inset) for dairy and nondairy treatments (N = 62). The average blood pressure was calculated as total AUC_{0–3.5 h} (h × mmHg) or divided by 3.5 h (inset). Abbreviations: AUC, area under the curve; DBP, diastolic blood pressure; h, hour(s); SBP, systolic blood pressure; SD, standard deviation; SEM, standard error of the mean.