AUCKLAND, New Zealand—Vitamin D improved insulin resistance in insulin-resistant women in a new study published in the British Journal of Nutrition (2009 Sep 28:1-7). The randomized, controlled, double-blind study administered supplements of 4,000 IU vitamin D3 (n=42) or placebo (n=39) daily for 6 months to South Asian women, aged 23 to 68 years. The women in the study were insulin resistant and had serum 25-hydroxyvitamin D3 (25(OH)D3) concentration of less than 50 nmol/l.
Median serum 25(OH)D3 increased significantly from 21 to 75 nmol/l with supplementation. Similar increased were seen for the women the 25th and 75th percentiles. Women in the 25th percentile experienced serum 25(OH)D3 increases from 11 to 55 nmol/l; and those in the 75th percentile saw a jump from 40 to 84 nmol/l.
Significant improvements were seen in insulin sensitivity and insulin resistance (P = 0.003 and 0.02, respectively), and fasting insulin decreased (P = 0.02) with supplementation compared with placebo. Insulin resistance was most improved serum 25(OH)D levels reached at least 80 nmol/l. Supplementation did not change insulin secretion.
Researchers stated this provided “further evidence for an increase in the recommended adequate levels.”
