Vitamin D Improves Insulin Resistance

AUCKLAND, New ZealandImproving vitamin D status in insulin resistant women resulted in improved insulin resistance (IR) and sensitivity, but no change in insulin secretion (Br J Clin Nutr. 2009) (DOI:10.1017/S0007114509992017). Researchers investigated the effect of improved vitamin D status on insulin resistance (IR), utilizing randomized, controlled, double blind intervention administering 100 g/d (4,000 IU) vitamin D3 (n=42) or placebo (n=39) for six months to South Asian women, aged 23 to 68. Subjects were insulin resistant and had serum 25-hydroxyvitamin D (25(OH)D) concentration of less than 50 nmol/l. Median serum 25(OH)D3 increased significantly from 21  to 75 nmol/l with supplementation. Significant improvements were seen in insulin sensitivity and IR (P=0.003 and P=0.02, respectively), and fasting insulin decreased (P=0.02) with supplementation compared with placebo. There was no change in C-peptide with supplementation. IR was most improved when endpoint serum 25(OH)D reached 80 nmol/l. Secondary outcome variables (lipid profile and high sensitivity C-reactive protein) were not affected by supplementation. Optimal vitamin D concentrations for reducing IR were shown to be 80 to 119 nmol/l, providing further evidence for an increase in the recommended adequate levels.