Baseline serum 25-hydroxy vitamin D is predictive of future glycemic status and insulin resistance: the Medical Research Council Ely Prospective Study 1990-2000.

Description

Recent evidence suggests that hypovitaminosis D is associated with hyperglycemia, insulin resistance, and type 2 diabetes. Using prospective data from the Ely Study, Forouhi et al. investigated the prospective association between serum 25-hydroxyvitamin D [25(OH)D] concentration (which reflects vitamin D status from both sun and dietary sources) and markers of type 2 diabetes risk, such as glucose and insulin concentrations, insulin resistance, and metabolic syndrome, in a sample of 524 nondiabetic men and women aged 40-69 years at baseline. Baseline 25(OH)D concentrations were negatively related with 1-year risk of hyperglycemia, insulin resistance, and metabolic syndrome after adjustment for several confounders. Moreover, further adjustments for insulin-like growth factor-1, parathyroid hormone, calcium, physical activity, and social class did not affect these relationships. These observations are important for understanding the etiology of altered glucose metabolism and type 2 diabetes risk and are hypothesis generating. They warrant further investigation in larger prospective randomized controlled trials with vitamin D supplementation. This paper was accompanied by a commentary by Robert Scragg who reviewed the literature on vitamin D with glucose-insulin homeostasis and type 2 diabetes. He highlighted the strengths of the Ely Study, citing its prospective design, the use of 25(OH)D concentration to measure vitamin D, the community-based sampling to increase the generalization of results, and the multiple statistical adjustments for several potential confounders. However, one of its major limitations was the 50% loss of subjects over the 10-year follow-up. Scragg suggested that further studies are required to assess baseline vitamin D status using 25(OH)D measurement to reproduce findings of the Ely Study. Glucose clamp studies are also necessary to understand the mechanism by which vitamin D influences plasma glucose-insulin homeostasis. Finally, well-designed clinical studies on the effect of vitamin D supplementation on glycemic status and diabetes risk are clearly warranted.