The effects of calcium and vitamin D supplementation on blood glucose and markers of inflammation in nondiabetic adults.
OBJECTIVE
We 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 > or =65 years.


METHODS
A total of 314 Caucasian adults without diabetes received either 500 mg calcium citrate and 700 IU vitamin D(3) 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.


RESULTS
The effects of combined calcium-vitamin 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 5.6-6.9 mmol/l, n = 92) at baseline. Among participants with IFG at baseline, those who took combined calcium-vitamin 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.


CONCLUSIONS
In 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.
Pittas
Anastassios G
AG
Department of Endocrinology, Diabetes, and Metabolism, Tufts-New England Medical Center, Boston, MA 02111, USA. apittas@tufts-nemc.org
Harris
Susan S
SS
Stark
Paul C
PC
Dawson-Hughes
Bess
B
D000368:Aged; D015415:Biomarkers / Q000097:blood*; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D015992:Body Mass Index; D001835:Body Weight; D002136:Calcium, Dietary / Q000494:pharmacology*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D006943:Hyperglycemia / Q000517:prevention & control; D007249:Inflammation / Q000097:blood; D007328:Insulin / Q000502:physiology; D008297:Male; D012016:Reference Values; D014807:Vitamin D / Q000494:pharmacology*
D015415:Biomarkers; D001786:Blood Glucose; D002136:Calcium, Dietary; D007328:Insulin; D014807:Vitamin D