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United States Department of Agriculture

Agricultural Research Service

Research Project: BONE HEALTH IN THE ELDERLY

Location: Human Nutrition Research Center on Aging

Title: The effects of vitamin D and calcium supplementation on pancreatic beta cell function, insulin sensitivity and glycemia in adults at high risk for diabetes. The CaDDM Randomized Controlled Trial

Authors
item Mitri, Joanna -
item Dawson-Hughes, Bess -
item Hu, Frank B. -
item Pittas, Anastassios -

Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 2011
Publication Date: August 1, 2011
Citation: Mitri, J., Dawson-Hughes, B., Hu, F., Pittas, A. 2011. The effects of vitamin D and calcium supplementation on pancreatic beta cell function, insulin sensitivity and glycemia in adults at high risk for diabetes. The CaDDM Randomized Controlled Trial. American Journal of Clinical Nutrition. 94(2):486-494.

Interpretive Summary: Inadequate intakes of vitamin D and calcium have been associated with higher risk of type 2 diabetes in observational studies but evidence from trials is lacking. The objective of this study was to determine whether vitamin D supplementation, with or without calcium, improves glucose homeostasis in adults at high risk for diabetes. Ninety two adults were randomized to either vitamin D (2,000 IU daily) or placebo and also to either calcium carbonate (400 mg twice daily) or placebo for 16 weeks. Change in pancreatic beta cell function, as measured by the disposition index, was measured at the beginning and end of the study. The Disposition index increased in the vitamin D group and decreased in the no vitamin D group (adjusted mean change +/- SE 300+/-130 vs. -126+/-127, respectively; p=0.011), which was explained by an improvement in insulin secretion (62+/-39 vs. -36+/-37 respectively; p=0.046). There was no significant difference in any outcomes with calcium vs. no calcium. We conclude that in adults at risk for type 2 diabetes, short-term supplementation with vitamin D improved insulin secretion. Longer term intervention studies are needed to determine whether supplemental vitamin D will retard the progression from pre-diabetes to diabetes in participants at high risk for the disease.

Technical Abstract: Suboptimal vitamin D and calcium status has been associated with higher risk of type 2 diabetes in observational studies but evidence from trials is lacking. The objective of this trial was to determine whether vitamin D supplementation, with or without calcium, improves glucose homeostasis in adults at high risk for diabetes. Ninety-two adults were randomized in a 2-by-2 factorial design double-masked placebo-controlled trial to either cholecalciferol (2,000 international units once daily) or calcium carbonate (400 mg twice daily) for 16 weeks. Primary outcome was change in pancreatic beta cell function, as measured by the disposition index after an intravenous glucose tolerance test. Other outcomes were acute insulin response, insulin sensitivity and measures of glycemia. Participants had a mean age of 57 years, BMI of 32 kg/m**2 and hemoglobin A1c of 5.9%. There was no significant vitamin D x calcium interaction on any outcomes. Disposition index increased in the vitamin D group and decreased in the no vitamin D group (adjusted mean change+/-SE 300+/-130 vs. -126+/-127 respectively; p=0.011), which was explained by an improvement in insulin secretion (62+/-39 vs. -36+/-37 respectively; p=0.046). Hemoglobin A1c rose less, but non-significantly, in the vitamin D compared to the no vitamin D group (0.06+/-0.03% vs. 0.14+/-0.03% respectively; p=0.081). There was no significant difference in any outcomes with calcium vs. no calcium. In adults at risk for type 2 diabetes, short-term supplementation with cholecalciferol improved beta cell function and had a marginal effect on attenuating the rise in hemoglobin A1c.

Last Modified: 4/17/2014
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