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) [1]. 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.
References:
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]
