Dietary protein, dairy, yogurt, and risk of high blood pressure and subsequent cardiovascular disease in middle-aged adults

Abstract

High blood pressure (HBP) is a primary risk factor for cardiovascular disease (CVD). Identification of modifiable dietary risk factors for HBP is crucial. The objective of this dissertation is to estimate the effects of long-term protein, dairy, and yogurt intakes on risk of HBP and subsequent CVD risk among those with HBP.

Data from four prospective studies of middle-aged adults were used: the Framingham Offspring Study (FOS) (n=1,361), Nurses’ Health Study (NHS) (n=66,987), NHS II (n=84,368), and Health Professionals Follow-Up Study (HPFS) (n=30,512). Diet was assessed via 3-day diet records in FOS and semi-quantitative food frequency questionnaires in NHS, NHS II, and HPFS. HBP was assessed by mercury sphygmomanometer or anti-hypertensive medication use in FOS and self-report in NHS, NHS II, and HPFS. Self-reported incident CVD was validated by physician review in the NHS and HPFS. Cox proportional hazard models were used to calculate hazard ratios, 95% confidence intervals (CI) associated with cumulative average dairy intakes while controlling for potential confounding by age, sex, height, activity, smoking, energy, diet quality scores, fruits and vegetables (FV), fiber, and fat intake.

Higher total protein intake led to a 40% (95% CI: 0.45-0.78) HBP risk reduction in FOS. When combined with higher FV or fiber consumption, higher protein intake resulted in a HBP risk reduction of 39% and 51%, respectively. Higher total dairy (3-<6 s/day) led to 13% (95% CI: 0.83-0.92; p-trend<0.0001), 26% (95% CI: 0.69-0.78; p-trend<0.0001), and 9% (95% CI: 0.84-0.98; p-trend<0.0001) reduced HBP risks across NHS, NHS II, and HPFS, respectively. In pooled analyses across these cohorts, higher total dairy (3-<6 s/day) or yogurt (≥5 s/week) intakes in combination with higher diet quality scores resulted in 23% (95% CI: 0.73-0.80) and 31% (95% CI: 0.65-0.74) HBP risk reductions, respectively. Among hypertensives, regular yogurt consumers (≥2 s/week) had statistically significant 17% and 18% lower risks of CVD in NHS and HPFS, respectively; HPFS men consuming 2-<6 s/d of total dairy also had an 11% lower CVD risk.

These results suggest that higher usual intakes of total protein, dairy and yogurt have beneficial effects on HBP risk and subsequent CVD in middle-aged adults.