Diabetes Care 30:980-986, 2007 DOI: 10.2337/dc06-1994 © 2007 by the American Diabetes Association
The Effects of Calcium and Vitamin D Supplementation on Blood Glucose and Markers of Inflammation in Nondiabetic Adults
1 Department of Endocrinology, Diabetes, and Metabolism, TuftsNew England Medical Center, Boston, Massachusetts Address correspondence and reprint requests to Anastassios G. Pittas, MD, M.Sc., Department of Endocrinology, Diabetes, and Metabolism, TuftsNew England Medical Center, 750 Washington St., 268, Boston, MA 02111. E-mail: apittas{at}tufts-nemc.org
OBJECTIVEWe sought to compare the effects of combined calcium and vitamin D supplementation versus placebo on blood glucose and markers of inflammation in nondiabetic adults aged RESEARCH DESIGN AND METHODSA total of 314 Caucasian adults without diabetes received either 500 mg calcium citrate and 700 IU vitamin D3 or placebos daily for 3 years in a double-blind, randomized, controlled trial designed for bone-related outcomes. In a post hoc analysis, fasting plasma glucose (FPG), insulin sensitivity (estimated by homeostasis model assessment of insulin resistance [HOMA-IR]), plasma C-reactive protein, and interleukin-6, were measured at baseline and 3 years. RESULTSThe effects of combined calciumvitamin D supplementation on 3-year change in FPG depended on baseline FPG (P = 0.02 for interaction). Therefore, we conducted analyses separately in participants with normal fasting glucose (NFG) (FPG <5.6 mmol/l, n = 222) and impaired fasting glucose (IFG) (FPG 5.66.9 mmol/l, n = 92) at baseline. Among participants with IFG at baseline, those who took combined calciumvitamin D supplements had a lower rise in FPG at 3 years compared with those on placebo (0.02 mmol/l [0.4 mg/dl] vs. 0.34 mmol/l [6.1 mg/dl], respectively, P = 0.042) and a lower increase in HOMA-IR (0.05 vs. 0.91, P = 0.031). In the NFG subgroup, there was no difference in the change in FPG or HOMA-IR between the two treatment arms. There were no differences in C-reactive protein or interleukin-6 between the two treatment arms in either subgroup. CONCLUSIONSIn healthy, older adults with IFG, supplementation with calcium and vitamin D may attenuate increases in glycemia and insulin resistance that occur over time. However, our findings should be considered hypothesis generating and need to be confirmed in randomized trials specifically designed for the outcomes of interest.
Abbreviations: FPG, fasting plasma glucose HOMA-IR, homeostasis model assessment of insulin resistance IFG, impaired fasting glucose NFG, normal fasting glucose PTH, parathyroid hormone
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