Associations of Plasma 25-Hydroxy Vitamin D and Dietary Vitamin D Intake with Insulin Resistance in Healthy Japanese Women

We investigated the associations of plasma 25-hydroxy vitamin D (25(OH)D) concentration and the dietary intake of vitamin D with insulin resistance in Japanese women. Study participants were 406 Japanese women attended a health examination. They were not taking hormones or medications for diabetes and had no history of cancer, ischemic heart disease, or stroke. Information regarding medical history and lifestyle factors was obtained by a self-administered questionnaire, while hours of sun exposure were determined through interviews. Dietary intake of vitamin D was evaluated using a validated food frequency questionnaire. Fasting plasma glucose and insulin concentrations were measured, and insulin resistance (HOMA-IR) scores were calculated based on homeostasis model assessment. Women with vitamin D deficiency (25(OH)D