Effects of soybean product intake on fasting and postload hyperglycemia and type 2 diabetes in Japanese men with high body mass index: The Saku Study

AIMS/INTRODUCTION: The inverse association between soybean intake and type 2 diabetes mellitus has been reported. We investigated the effects of soybean product intake on the incidence of type 2 diabetes mellitus considering fasting and postload hyperglycemia. MATERIALS AND METHODS: The present 4‐year, cohort study included 1,738 men and 1,301 women, aged 30–69 years, without diabetes mellitus at baseline who underwent comprehensive medical check‐ups between April 2006 and March 2007 at Saku Central Hospital. Participants were stratified by sex and body mass index (BMI), and further classified into three groups based on soybean product intake: group 1 (0–1 time/week), group 2 (2–3 times/week) and group 3 (four or more times per week). Participants underwent annual standard 75‐g oral glucose tolerance testing during follow‐up periods until March 2011. Main outcomes were incidence of fasting hyperglycemia, postload hyperglycemia and type 2 diabetes mellitus. RESULTS: During 10,503 person‐years of follow up, 204 participants developed type 2 diabetes mellitus, including 61 who developed fasting hyperglycemia and 147 who developed postload hyperglycemia. Among men with a high BMI, group 3 had significantly lower risk for the incidence of type 2 diabetes mellitus, fasting hyperglycemia and postload hyperglycemia than group 1, and multivariable‐adjusted hazard ratios and 95% confidence intervals were 0.44 (0.22–0.89), 0.36 (0.15–0.96) and 0.40 (0.18–0.92), respectively. Similar results were not observed among men with low BMI or women. CONCLUSIONS: Soybean product intake prevented fasting and postload hyperglycemia and type 2 diabetes mellitus in men with a high BMI. Further long‐term observation is necessary.