Effects of Combined Calcium and Vitamin D Supplementation on Insulin Secretion, Insulin Sensitivity and β-Cell Function in Multi-Ethnic Vitamin D-Deficient Adults at Risk for Type 2 Diabetes: A Pilot Randomized, Placebo-Controlled Trial
What this study found
Overall, 6 months of calcium plus vitamin D did not improve insulin sensitivity, insulin secretion, or beta-cell function versus placebo in this vitamin D-deficient, diabetes-risk population. For HOMA2%S, the treatment group changed from 63.9 (29.0) at baseline to 61.1 (25.6) at 6 months, while placebo changed from 55.1 (30.4) to 52.5 (27.7); the treatment-by-time interaction was not significant (0.96, 0.10). Matsuda index, insulinogenic index, AUC for C-peptide, and disposition index were also not significantly different between groups. In post hoc analysis among participants with…
- Study & population
- Pilot randomized, placebo-controlled trial in multi-ethnic vitamin D-deficient adults at risk for type 2 diabetes in Melbourne, Australia.
- Intervention
- Participants in the active arm received oral vitamin D3 2,000 IU daily (two OstevitD capsules) plus elemental calcium 1,200 mg daily as calcium carbonate, taken with breakfast for 6 months.
- Key limitation
- This was a small pilot study with only 35 completers in the active arm, limiting power to detect modest effects.
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Open PDFOriginal abstract
Objectives To examine whether combined vitamin D and calcium supplementation improves insulin sensitivity, insulin secretion, β-cell function, inflammation and metabolic markers. Design 6-month randomized, placebo-controlled trial. Participants Ninety-five adults with serum 25-hydroxyvitamin D [25(OH)D] ≤55 nmol/L at risk of type 2 diabetes (with prediabetes or an AUSDRISK score ≥15) were randomized. Analyses included participants who completed the baseline and final visits (treatment n = 35; placebo n = 45). Intervention Daily calcium carbonate (1,200 mg) and cholecalciferol [2,000–6,000 IU to target 25(OH)D >75 nmol/L] or matching placebos for 6 months. Measurements Insulin sensitivity (HOMA2%S, Matsuda index), insulin secretion (insulinogenic index, area under the curve (AUC) for C-peptide) and β-cell function (Matsuda index x AUC for C-peptide) derived from a 75 g 2-h OGTT; anthropometry; blood pressure; lipid profile; hs-CRP; TNF-α; IL-6; adiponectin; total and undercarboxylated osteocalcin. Results Participants were middle-aged adults (mean age 54 years; 69% Europid) at risk of type 2 diabetes (48% with prediabetes). Compliance was >80% for calcium and vitamin D. Mean serum 25(OH)D concentration increased from 48 to 95 nmol/L in the treatment group (91% achieved >75 nmol/L), but remained unchanged in controls. There were no significant changes in insulin sensitivity, insulin secretion and β-cell function, or in inflammatory and metabolic markers between or within the groups, before or after adjustment for potential confounders including waist circumference and season of recruitment. In a post hoc analysis restricted to participants with prediabetes, a significant beneficial effect of vitamin D and calcium supplementation on insulin sensitivity (HOMA%S and Matsuda) was observed. Conclusions Daily vitamin D and calcium supplementation for 6 months may not change OGTT-derived measures of insulin sensitivity, insulin secretion and β-cell function in multi-ethnic adults with low vitamin D status at risk of type 2 diabetes. However, in participants with prediabetes, supplementation with vitamin D and calcium may improve insulin sensitivity. Trial Registration Australian New Zealand Clinical Trials Registry ACTRN12609000043235