Fermented Soy Product Intake Is Inversely Associated with the Development of High Blood Pressure: The Japan Public Health Center-Based Prospective Study

Background: Randomized controlled studies have investigated the short-term effect of soy product intake on blood pressure (BP) in normotensive people. To our knowledge, no prospective studies exist on the effect of habitual intake of fermented soy products, separate from total soy products, on BP in the general population. Objective: We examined the association between the habitual intake of soy products, including fermented soy products, and the development of high BP during a 5-y period among participants in a population-based prospective cohort study in Japan. Methods: The study included normotensive participants aged 40-69 y at baseline (926 men and 3239 women) who completed 2 questionnaires and whose BP was measured at the baseline survey between 1993 and 1994 and the 5-y follow-up in the Japan Public Health Center-Based Prospective Study Cohort II. The intake of soy products was assessed with a food-frequency questionnaire. High BP was defined as systolic blood pressure >= 130 mm Hg, diastolic blood pressure >= 85 mm Hg, or antihypertensive medication use. ORs and 95% CIs of high BP by frequency of soy products (miso, natto, and tofu) consumption, intake of total and fermented soy products, and intake of isoflavones from total and fermented soy products were estimated with the use of multiple logistic regression analysis. Results: Multivariable-adjusted ORs of high BP for the highest compared with the lowest tertile of total and fermented soy product intake were 1.03 (95% CI: 0.84, 1.25; P-trend = 0.786) and 0.72 (95% CI: 0.56, 0.92; P-trend = 0.009), respectively. The frequency of nonfermented soy product (tofu) intake was not associated with the development of high BP (P-trend = 0.597). Conclusions: The intake of fermented soy products, but not total or nonfermented soy products, was inversely associated with developing high BP in men and women with normal BP.