MedicalResearch.com Interview with: Isao Saito, MD, PhD Department of Basic Nursing and Health Science, Ehime University Graduate School of Medicine Toon, Ehime Medical Research: What is the background for this study? What are the main findings? Response: Type 2 diabetes is a major lifestyle-related disease with a rapid increasing prevalence in Japan. One meta-analysis of six cohort studies showed that an increase in daily food intake of 1.15 servings of green leafy vegetables was associated with a 14% reduction in the incidence of type 2 diabetes. Therefore, it is evident to think that green and yellow vegetables have beneficial effects against type 2 diabetes. Nonetheless, the relationship of their nutritive content with insulin resistance is poorly understood. We conducted the Toon Health Study initiated in 2009, which was a prospective cohort study of the Japanese general population. The cohort study was intended to characterize environmental risk factors related to incident diabetes and cardiovascular disease. Participants were recruited from the general population aged 30–79 years who were living in Toon City, Ehime Prefecture, Japan. Of them, we investigated 951 Japanese men and women aged 30–79 years who were not undergoing treatment for diabetes and measured their serum β-carotene and retinol concentrations. A 75-g oral glucose tolerance test was performed and the Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) and the Matsuda Index were calculated as measures of insulin resistance. Multivariable-adjusted odds ratios of the highest quartile of serum β-carotene compared with the lowest quartile for HOMA-IR >1.6 and Matsuda Index <4.9 were 0.56 (95% confidence interval, 0.34–0.94) and 0.62 (0.37–1.02), respectively. When stratified by sex and overweight status, these associations were observed for women and non-overweight individuals. Serum retinol concentration was not associated with either index. Furthermore, according to the nutritional survey, serum β-carotene concentration was associated with green and yellow vegetable intake (p = 0.01). (more…)