June 21, 2010 -- Vitamin D deficiency, long suspected to be a risk factor for glucose intolerance, is commonly found in people with poor diabetes control, according to a new study.
''Our study could not show cause and effect," says Esther Krug, MD, an endocrinologist at Sinai Hospital of Baltimore and assistant professor of medicine at Johns Hopkins University School of Medicine, Baltimore, who presented the findings at ENDO 2010, the annual meeting of The Endocrine Society, in San Diego.
Krug and her colleagues decided to look at vitamin D deficiency in the wake of reports suggesting that vitamin D has an active role in regulating pancreatic beta cells, which make insulin.
So they evaluated the medical charts of 124 people with type 2 diabetes (in which the body doesn't make enough insulin or the cells ignore the insulin) seen at an outpatient clinic from 2003 to 2008. The charts contained information on the patients' age, race, vitamin D levels, calcium intake, family history of diabetes, and results of their hemoglobin A1cblood test. The A1c provides an average measurement of blood sugar control over about a 12-week span. (For people with diabetes, the goal is 7%; for people without, the normal range is 4%-6%.)
Krug's team divided the vitamin D levels they found into four groups: normal (defined in the study as above 32 nanograms per deciliter), mild deficiency, moderate deficiency, or severe.
In all, 113 of the 124 patients (91.1%) were vitamin D deficient -- 35.5% severely, 38.7% moderately, and 16.9% mildly.
The average A1c was higher in patients with severe vitamin D deficiency compared to those with normal levels of vitamin D. Those with severe deficiency had an average of 8.1%; those with normal vitamin D levels averaged 7.1%.