Poor control of diabetes may be linked to low vitamin D

The results are being presented at The Endocrine Society's 92nd Annual Meeting in San Diego.

"This finding supports an active role of vitamin D in the development of Type 2 diabetes," said study co-author Esther Krug, MD, an assistant professor of medicine at The Johns Hopkins University School of Medicine and an endocrinologist at Sinai Hospital, Baltimore.

Krug and her colleagues reviewed the medical charts of 124 patients with Type 2 diabetes who came to an endocrine outpatient clinic for specialty care from 2003 to 2008. Patients' age ranged from 36 to 89 years. All patients had a single measurement of their serum 25-hydroxyvitamin D levels as part of their evaluation at the clinic. The researchers divided the patients into quartiles based on vitamin D level.

Despite receiving regular primary care visits before referral to the endocrine clinic, 91 percent of patients had either vitamin D deficiency (defined as a level below 15 nanograms per deciliter, or ng/dL) or insufficiency (15 to 31 ng/dL), the authors reported. Only about 6 percent of patients were taking vitamin D supplements at their first visit.

Additionally, the investigators found an inverse relationship between the patients' blood levels of vitamin D and their hemoglobin A1c value, a measure of blood sugar control over the past several months. Lower vitamin D levels were discovered in patients with higher average blood sugars as measured by HbA1c, Krug said. Compared with whites, blacks had a higher average A1c and lower average vitamin D level.

"Since primary care providers diagnose and treat most patients with Type 2 diabetes, screening and vitamin D supplementation as part of routine primary care may improve health outcomes of this highly prevalent condition," she said.