The effect of vitamin D supplementation on body composition in nursing mothers with overweight or obesity: a randomized double-blind placebo-controlled clinical trial

Abstract Background This study aimed to evaluate the effect of vitamin D3 supplementation on body composition and anthropometric measures of nursing mothers. Methods In a double-blind, randomized clinical trial, 90 nursing mothers with overweight or obesity were randomized into three groups for 12 weeks: two groups of vitamin D3 supplementation (2000 IU/d (VD1), n = 32 and 4000 IU/d (VD2), n = 29) and placebo (PL) group (n = 29). The information on body composition was obtained using the body impedance analysis (BIA) method. Serum 25-Hydroxy vitamin D (25(OH) D), Intact Parathyroid Hormone (iPTH), calcium, and phosphorus were measured before and after the intervention. Data were analyzed based on the intention-to-treat (ITT) method. Two-way repeated measure ANOVA (mixed ANOVA) was applied to assess whether the mean changes in the results from baseline to 12 weeks differ in the three groups. Results There was a significant increase in the serum 25(OH) D concentration in the VD2 group compared to VD1 and PL groups (mean change (MC), 12.3 ng/ml; 95% CI, 9.4/15.0, p-value < 0.001). In addition, fat mass (MC, − 4.3 kg; 95% CI, − 7.0/− 1.1, p-value < 0.007), fat mass index (MC, − 1.6; 95% CI, − 2.6/− 0.5, p-value < 0.006) and body fat percentage (MC, − 8.1; 95% CI, − 12.0/− 4.2, p-value < 0.007) reduced in VD2 group as compared with VD1 and PL groups. Conclusion The intake of 4000 IU/d vitamins D3 supplementation would elevate circulating 25(OH) D concentrations in nursing mothers with overweight or obesity and improve some indices of body composition. Trial registration Iranian Registry of Clinical Trials ( http://www.irct.ir : IRCT20140413017254N6) registered on 11-04-2018. Graphical Abstract The graphical abstract of this clinical trial, is a figure that explains the final results of the manuscript in a clear and attractive way