About this Journal Submit a Manuscript Table of Contents
International Journal of Endocrinology
Volume 2010 (2010), Article ID 351385, 18 pages
http://dx.doi.org/10.1155/2010/351385
Review Article

Role of Vitamin D in Insulin Secretion and Insulin Sensitivity for Glucose Homeostasis

1Department of Nutrition Sciences, University of Alabama at Birmingham, AL 35233, USA
2Department of Pediatrics, Division of Pediatric Endocrinology and Metabolism, The Children's Hospital, University of Alabama at Birmingham, AL 35233, USA

Received 20 April 2009; Accepted 16 June 2009

Academic Editor: Vin Tangpricha

Copyright © 2010 Jessica A. Alvarez and Ambika Ashraf. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Vitamin D functions are not limited to skeletal health benefits and may extend to preservation of insulin secretion and insulin sensitivity. This review summarizes the literature related to potential vitamin D influences on glucose homeostasis and insulin sensitivity. Cross-sectional data provide some evidence that circulating 25-hydroxyvitamin D (25(OH)D) is inversely associated with insulin resistance, although direct measurements of insulin sensitivity are required for confirmation. Reported associations with insulin secretion, however, are contradictory. Available prospective studies support a protective influence of high 25(OH)D concentrations on type 2 diabetes mellitus risk. There is a general lack of consistency in vitamin D intervention outcomes on insulin secretion and sensitivity, likely due to differences in subject populations, length of interventions, and forms of vitamin D supplementation. Vitamin D receptor gene polymorphisms and vitamin D interactions with the insulin like growth factor system may further influence glucose homeostasis. The ambiguity of optimal vitamin D dosing regimens and optimal therapeutic concentrations of serum 25(OH)D limit available intervention studies. Future studies, including cross-sectional and prospective, should be performed in populations at high risk for both vitamin D deficiency and type 2 diabetes mellitus. Well-designed, placebo-controlled, randomized intervention studies are required to establish a true protective influence of vitamin D on glucose homeostasis.