Sources of dietary protein and risk of hypertension in a general Dutch population

Evidence suggests a small beneficial effect of dietary protein on blood pressure (BP), especially for plant protein. We examined the relationship between several types of dietary protein (total, plant, animal, dairy, meat and grain) and the risk of hypertension in a general population of 3588 Dutch adults, aged 26-65 years, who were free of hypertension at baseline. Measurements were done at baseline and after 5 and 10 years of follow-up. Hazard ratios (HR), with 95% CI, for incident hypertension were obtained in tertiles of energy-adjusted protein, using time-dependent Cox regression models. Models were adjusted for age, sex, BMI, education, smoking, baseline systolic BP, dietary confounders and protein from other sources (if applicable). Mean BP was 118/76mmHg at baseline. Protein intake was 85 (SD 22) g/d (approximately 15% of energy) with 62% originating from animal sources. The main sources of protein were dairy products (28 %), meat (24 %) and grain (19 %). During the follow-up, 1568 new cases of hypertension were identified (44% of the participants). Energy-adjusted intake of total protein, plant protein and animal protein was not significantly associated with hypertension risk (all HR approximately 1.00, P>0.60). Protein from grain showed a significant inverse association with incident hypertension, with a HR of 0.85 (95% CI 0.73, 1.00, P-trend = 0.04) for the upper tertile (>= 18 g/d) v. the lower tertile (< 14 g/d), whereas dairy protein and meat protein were not associated with incident hypertension. In conclusion, higher intake of grain protein may contribute to the prevention of hypertension, which warrants confirmation in other population-based studies and randomised controlled trials.