Vitamin D Improves Insulin Resistance

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 or a placebo daily for six months to South Asian women, aged 23 to 68 years. The women in the study were insulin resistant and had serum 25-hydroxyvitamin 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, and fasting insulin decreased with supplementation compared with placebo. Insulin resistance was most improved in cases where 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.”