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.

BACKGROUND: Prediabetes is a public health concern, and its prevalence is growing around the world. Providing an effective strategy to prevent prediabetes progression and, consequently, type-2 diabetes mellitus (T2DM) could be useful for global health. The present study aimed to investigate the impact of vitamin D supplementation on metabolic factors, serum omentin-1 levels, and anthropometric indices in women with prediabetes. METHODS: This randomized controlled trial (RCT) study was carried out on women with prediabetes aged 18-65 years. The women were allocated to the intervention (n = 48) or placebo (n = 48) groups to receive vitamin D (50000 IU) or a placebo every two weeks for 12 weeks, respectively. Fasting blood samples, anthropometric measurements, and information about the dietary intake and physical activity of the participants were collected at the beginning and after the intervention. Data analyses were done using IBM SPSS Statistics software. RESULTS: Vitamin D intervention significantly enhanced 25-hydroxyvitamin D (MD (CI 95%): 11.610 ng/ml (8.264, 14.956)), insulin (MD (CI 95%): 0.413 µIU/mL (0.321, 0.505)), Homeostatic Model Assessment of Insulin Resistance (MD (CI 95%): 0.411 (0.319, 0.502)), and Homeostatic Model Assessment of Insulin Resistance-β cell function (MD (CI 95%): 29.505% (22.114, 36.986)) levels compared to the placebo at the end of trial (all, p < 0.05). Moreover, a significant reduction in QUICKI was observed after the intervention (MD (CI 95%): -0.062 (-0.076, -0.048)). Changes in fasting blood sugar (FBS), lipid profiles, omentin-1 levels, and anthropometric indices were not significant between the groups after the intervention. CONCLUSION: The findings revealed that vitamin D administration improved insulin secretion but failed to affect FBS, lipid profiles, anthropometric indices, and body composition in women with prediabetes. Due to inconsistent results, more well-designed RCTs are required to clarify the effects of vitamin D supplementation on these patients.