Summary: In women aged 18–65 with prediabetes, vitamin D 50,000 IU every two weeks for 12 weeks improved insulin secretion and HOMA-IR but did not change fasting glucose, lipids, anthropometry, or omentin-1 compared with placebo.
PICO Summary
| Element | Detail |
|---|---|
| Population | Women aged 18–65 with prediabetes (n=96; 48 per arm). |
| Intervention | Vitamin D 50,000 IU every two weeks for 12 weeks. |
| Comparison | Matching placebo on an identical schedule. |
| Outcome | Significant rise in 25(OH)D, insulin (MD 0.413 µIU/mL), HOMA-IR (MD 0.411) and HOMA-β (MD 29.5%). No significant change in fasting glucose, lipid profile, omentin-1, or anthropometric indices. |
Vitamin D in prediabetes
RCT · women with prediabetes · 12 weeks
Vitamin D raised insulin and HOMA indices but left fasting glucose, lipids, omentin-1, and anthropometry unchanged. Biochemistry moved; the clinical glucose needle did not.
Expert Commentary
Vitamin D for diabetes prevention is a question I thought the large trials had largely settled, and not in vitamin D’s favour, so I came to this study expecting little and found a familiar pattern. The biochemistry moved, the clinical needle did not. Insulin and HOMA indices improved, which is mechanistically plausible given vitamin D receptors on beta cells, but fasting glucose, the thing I actually track in a prediabetic woman, did not budge. That disconnect is the whole story, and it echoes the much larger D2d trial, where supplementation failed to prevent progression to diabetes except perhaps in those who started deficient. The limitation that matters most here is that baseline vitamin D status was not reported, so I cannot tell whether I am looking at genuine repletion of deficient women or supplementation of replete ones, and that distinction is everything. Can I use this with my patients? Only in the way I already do: correct documented deficiency because it is worth doing on its own merits, but never sell vitamin D as a diabetes-prevention strategy in place of weight loss, activity, or metformin. I would need hard progression data, not HOMA shifts, to change that stance.
References
Molani-Gol R, Rafraf M, Asghari Jafarabadi M, Aftabi-Yousefabad S. Effects of vitamin D supplementation on metabolic factors, serum omentin-1, and anthropometric indices in middle-aged women with prediabetes: a double-blind randomized controlled trial. Nutr Diabetes. 2025;15(1):44. doi:10.1038/s41387-025-00402-w