Dietary soy and natto intake and cardiovascular disease mortality in Japanese adults: the Takayama study

Background: Whether soy intake is associated with a decreased risk of cardiovascular disease (CVD) remains unclear. A traditional Japanese soy food, natto, contains a potent fibrinolytic enzyme. However, its relation to CVD has not been studied. Objective: We aimed to examine the association of CVD mortality with the intake of natto, soy protein, and soy isoflavones in a population-based cohort study in Japan. Design: The study included 13,355 male and 15,724 female Takayama Study participants aged >= 35 y. At recruitment in 1992, each subject was administered a validated semiquantitative food-frequency questionnaire. Deaths from CVD were ascertained over 16 y. Results: A total of 1678 deaths from CVD including 677 stroke and 308 ischemic heart disease occurred during follow-up. The highest quartile of natto intake compared with the lowest intake was significantly associated with a decreased risk of mortality from total CVD after control for covariates: the HR was 0.75 (95% CI: 0.64, 0.88, P-trend = 0.0004). There were no significant associations between the risk of mortality from total CVD and intakes of total soy protein, total soy isoflavone, and soy protein or soy isoflavone from soy foods other than natto. The highest quartiles of total soy protein and natto intakes were significantly associated with a decreased risk of mortality from total stroke (HR = 0.75, 95% CI: 0.57, 0.99, P-trend = 0.03 and HR = 0.68, 95% CI: 0.52, 0.88, P-trend = 0.0004, respectively). The highest quartile of natto intake was also significantly associated with a decreased risk of mortality from ischemic stroke (HR = 0.67, 95% CI:0.47, 0.95, P-trend = 0.03). Conclusion: Data suggest that natto intake may contribute to the reduction of CVD mortality.