Could Vitamin D Improve Type 2 Diabetes Outcomes?
Vitamin D supplementation does not affect insulin secretion rate (ISR) or hemoglobin A1c (HbA1c) in metformin-treated patients with well-controlled type 2 diabetes, according to recent findings.
Researchers arrived at this conclusion following the completion of the Vitamin D for Established Type 2 Diabetes (DDM2) Study, which included 127 patients with stable diabetes—defined as an HbA1c of 7.5% or lower—that was managed with lifestyle modifications only or lifestyle modifications plus metformin.
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Participants were randomly assigned to receive either 4000 IU vitamin D3 per day or placebo for a period of 48 weeks. Results of peripheral plasma C-peptide levels after 3-hour 75-g oral glucose tolerance testing at baseline and 24 weeks were used to estimate ISR. Changes in HbA1c were recorded at 16, 24, 36, and 48 weeks.
At baseline, mean plasma 25-hydroxyvitamin D [25(OH)D] concentration was 26.6 ng/mL and mean HbA1c was 6.6%. Ultimately, results of the study showed that 25(OH)D changed by 20.5 ng/mL in the vitamin D group vs −1.6 ng/mL in the placebo group, but that there was no between-group difference in change in ISR or HbA1c.
Notably, among patients treated with lifestyle only (n = 28), vitamin D supplementation was associated with a reduction in HbA1c vs placebo ((−0.1% vs 0.3%) at week 24. However, “this result was not observed at the other time points and could be due to chance” the researchers wrote.
—Christina Vogt
Reference:
Angellotti E, D’Alessio D, Dawson-Hughes B, et al. Vitamin D supplementation in patients with type 2 diabetes: the Vitamin D for established type 2 diabetes (DDM2) study. J Endocr Soc. 2018;2(4):310-321. https://doi.org/10.1210/js.2018-00015.
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