Association between total soy product intake and metabolic syndrome in middle-aged Japanese workers: Cross-sectional and longitudinal study findings

The aim of this study was to determine the association between total soy product intake and metabolic syndrome (MetS) in Japanese workers. The cross-sectional study included 698 participants aged over 40 years, and the longitudinal study included 527 participants aged over 40 years in 2012 who participated at least once from 2013 to 2018. Dietary intake of total soy products was summed based on the total amount of 12 kinds of soy products assessed using a food frequency questionnaire. Participants were diagnosed as having MetS if they had abdominal obesity and at least one of the following conditions:hypertriglyceridemia, high blood pressure, and hyperglycemia. To calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for MetS according to tertile of total soy product intake, multivariable logistic regression was performed for the cross-sectional analysis, and generalized estimating equations were used for the longitudinal analysis. Cross-sectional analysis showed that there was an inverse association between total soy product intake and MetS, and the OR of tertile 3 was significantly higher than that of tertile 1. However, the inverse association disappeared in the longitudinal analysis. Further long-term studies are needed to determine the association between total soy product intake and MetS. J. Med. Invest. 72 : 343-353, August, 2025.