Relations between protein intake and blood pressure in Japanese men and women: the Circulatory Risk in Communities Study (CIRCS).

BACKGROUND An inverse association between protein intake and blood pressure has been reported in Western countries. However, the evidence is limited for Asians, whose protein sources are different from those in Western populations. OBJECTIVES The objective was to examine the association between protein intake and blood pressure in Japanese adults. METHODS We conducted a population-based, cross-sectional study of 7585 subjects (3499 men and 4086 women) from 40 to 69 y of age living in 5 communities in Japan. Dietary intakes of total, animal, and plant protein were estimated by a single 24-h dietary recall. We then examined the associations between dietary intake of those proteins and blood pressure after adjustment for age, sex, community, body mass index, antihypertensive medication use, ethanol intake, smoking, and dietary intakes of sodium, potassium, and calcium. RESULTS After adjustment for cardiovascular disease risk factors, a 25.5-g/d increment in total protein intake was associated with a decrease in systolic blood pressure of 1.14 mm Hg (P < 0.001) and in diastolic blood pressure of 0.65 mm Hg (P < 0.001), and a 19.9-g/d increment in animal protein intake was associated with a decrease in systolic blood pressure of 1.09 mm Hg (P < 0.001) and in diastolic blood pressure of 0.41 mm Hg (P = 0.003). A 13.1-g/d increment in plant protein intake was associated with a decrease in diastolic blood pressure of 0.57 mm Hg (P < 0.001). Further adjustment for nutritional factors weakened these associations, but the inverse associations of total protein intake with diastolic blood pressure and of animal protein intake with systolic blood pressure remained statistically significant. CONCLUSION Total and animal protein intakes were inversely associated with blood pressure in Japanese adults.