Low vitamin D levels may be associated with diabetes; supplementation trials needed

Key Points

New studies confirm that lower levels of vitamin D are associated with a higher risk of developing diabetes and diabetic retinopathy. But the mechanisms by which vitamin D may affect progression, beta cell function, dysglycemia, and retinopathy are not clear. Researchers say prospective vitamin D supplementation trials are the next step, not ad hoc treatment with vitamin D.

"We see an inverse association with serum vitamin D levels and diabetic retinopathy in children with type 1 diabetes," said Maria Craig, PhD, School of Women's and Children's Health, University of New South Wales, Sydney, Australia. "But it is unclear why and our results do not suggest wholesale vitamin D supplementation for anyone, child or adult, with diabetes."

Dr Craig presented 1 of 3 studies linking lower serum levels of vitamin D with increased risk for diabetes or diabetes complications at the American Diabetes Association's 71st Scientific Sessions in San Diego. Her group found that children with type 1 diabetes who were deficient in vitamin D at double the risk for retinopathy compared to similar children with normal serum levels of vitamin D. Vitamin D deficiency was not associated with abnormal peripheral nerve function or elevated albumin excretion rate/albumin-to-creatinine ratio. Her results echo earlier findings in adults with type 2 diabetes. Biologic models suggest that increased levels of vitamin D inhibit neovascularization and angiogenesis, which protects the retina, but there are no clinical data.

Canadian researchers found an association between higher levels of vitamin D and improved beta-cell function and lower glucose levels after 3 years of follow up. Higher baseline vitamin D significantly reduced the odds ratio for progression to type 2 diabetes even after adjustment for baseline body mass index (BMI) and changes to BMI over the 3-year follow-up period.