In a recent post I highlighted a study which has found that higher vitamin D levels are associated with a reduced risk of death. This evidence actually comes on the back of other studies showing the same thing, and while therefore strengthens the association between vitamin D and death risk, cannot be used to claim that increasing vitamin D levels will help prevent death. One of the points I made in this post is that what is required is randomised controlled trials which give individuals vitamin or placebo, to see if vitamin D therapy can genuinely help to prevent disease and death.
I’m generally on the look-out for randomised controlled studies, and last week reported on a review of relevant studies showing that vitamin D supplementation has the ability to help prevent falls in the elderly. This week, I’ve come across a randomised controlled study in which the effects of vitamin D supplementation were tested in a group of women suffering from insulin resistance (a precursor of type 2 diabetes) . In this study, 81 women of south-Asian descent and with low vitamin D levels (less than 20 ng/ml or 50 mmol/l) were treated with 4000 IU of vitamin D3 or placebo each day for a period of 6 months.
Vitamin D supplementation caused vitamin D levels to rise from an average of 8.4 ng/ml (21 mmol/l) to 30 ng/ml (75 nmol/l).
Compared to those taking the placebo, those taking the vitamin D enjoyed improvements in insulin sensitivity and resistance (improved sensitivity and reduced resistance).
Optimal vitamin D levels were found to be between 32 and 48 ng/ml (80 – 119 nmol/l), which, according to the authors, provides further evidence for an increase in the recommended adequate levels.
The results of this study suggest quite strongly that optimising vitamin D levels may help to guard against type 2 diabetes, and this may have particular relevance for those of south Asian descent, as such individuals appear to be at heightened risk of this condition.
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 randomised, placebo-controlled trial. Br J Nutr 28 September 2009 [Epub ahead of print publication]