Association of A1C Levels With Vitamin D Status in U.S. Adults: Data from the National Health and Nutrition Examination Survey

OBJECTIVE: Data relating vitamin D status with indices of glucose homeostasis as manifested by A1C in the U.S. adult population are few. RESEARCH DESIGN AND METHODS: We examined the association between serum 25 hydroxyvitamin D [25(OH)D] and A1C levels in 9,773 adults (age ≥18 years old) participating in the 2003–2006 National Health and Nutrition Examination Survey. Multivariate linear regression analyzed the association after accounting for potential confounders. RESULTS: Serum 25(OH)D levels were inversely associated with A1C levels in subjects age 35–74 years (P = 0.0045) and those who did not report a history of diabetes (P = 0.0282). CONCLUSIONS: These findings support a mechanistic link between serum vitamin D concentrations, glucose homeostasis, and the evolution of diabetes in a large segment of the U.S. adult population. Screening people with elevated A1C levels for vitamin D insufficiency should be considered.