Vitamin D supplements show anti-diabetes potential

Supplements of vitamin D may improve risk factors for diabetes such as insulin resistance and sensitivity, says a new study.

The study involved 81 South Asian women with insulin resistance (1). The subjects, aged between 23 and 68, were randomly assigned to receive either 100 micrograms (4,000 IU) of vitamin D3 or placebo daily for six months. At the end of the test period, women in the vitamin D group experienced significant improvements in both insulin sensitivity and resistance, said the researchers, which was also accompanied a decrease in fasting insulin levels, compared to placebo.

Insulin resistance, a condition in which normal amounts of insulin are inadequate to produce a normal insulin response from fat, muscle and liver cells, was significantly lower in women following high-dose vitamin D supplementation, according to results of the randomized, controlled, double-blind trial. The optimal effects were observed when blood vitamin D levels were in the range 80 to 119 nanomoles per liter, said the researchers, providing further evidence for an increase in the recommended adequate levels.

This is not the first time that vitamin D has been linked to diabetes: a meta-analysis of data from observational studies and clinical trials in adults showed a relatively consistent association between low intakes of calcium, vitamin D, or dairy intake and type-2 diabetes (2).

1. von Hurst PR et al. Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and vitamin D deficient – a randomized, placebo-controlled trial. British Journal of Nutrition. 2009; 1–7.
2. Pittas AG et al. The role of vitamin D and calcium in type 2 diabetes. A Systematic Review and Meta-AnalysisJournal of Clinical Endocrinology & Metabolism. 2007; 92:2017–2029.