Serum 25-Hydroxy Vitamin D and Insulin Resistance, Metabolic Syndrome, and Glucose Intolerance Among Arab Americans

OBJECTIVE: To describe 25-hydroxy vitamin D (25-OH-D) levels and examine associations between 25-OH-D levels and insulin resistance (IR), metabolic syndrome (MS), and glucose intolerance in Arab Americans. RESEARCH DESIGN AND METHODS: Serum 25-OH-D levels were measured in a representative, cross-sectional sample of 542 Arab Americans with IR (46%), MS (33%), and glucose intolerance (42%). RESULTS: Vitamin D insufficiency (5 to <20 ng/ml) was present in 75% and hypovitaminosis D (20 to <40 ng/ml) in 24% of participants. In men, 25-OH-D levels were lower in those with glucose intolerance than normoglycemia (P = 0.01). No such difference was found in women. In men, 25-OH-D was negatively correlated with homeostasis model assessment of insulin resistance (r = -0.19; P = 0.0043), triglycerides (r = -0.18; P = 0.0069), fasting plasma glucose (r = -0.15; P = 0.027), and A1C (r = -0.14; P = 0.038). In women, 25-OH-D was positively correlated with HDL (r = 0.19; P = 0.0008). CONCLUSIONS: Vitamin D insufficiency and hypovitaminosis D are extremely common among Arab Americans, and they are associated with IR, components of the MS, and glucose intolerance in men.