Vitamin D levels inversely correlated with incident diabetes in US women
MedWire News: Blood levels of vitamin D are inversely associated with the risk for developing Type 2 diabetes in women, independently of other risk factors, a case-control study suggests.
The authors of the study call for randomized, controlled trials to test the hypothesis that vitamin D supplementation might reduce incident diabetes.
Anastassios Pittas (Tufts Medical Center, Boston, Massachusetts, USA) and colleagues conducted a nested case-control study among 1167 women who participated in the Nurses' Health Study. Their mean age was 56.5 years, mean body mass index (BMI) was 27.8 kg/m2, and mean plasma 25-hydroxyvitamin D (25-OHD) was 22.7 ng/ml.
In all, 608 of the women were newly diagnosed with Type 2 diabetes (cases), while the remainder were free of diabetes (controls), but matched by age and race.
Total vitamin D intake was 321 IU/day and did not differ between cases and controls. However, after adjusting for multiple confounders, the odds ratio (OR) for incident diabetes for those in the top (median 33.4 ng/ml) versus the bottom (median 14.4 ng/ml) quartile of 25-OHD concentration was 0.52, with a highly significant p-value.
Further analyses revealed no apparent threshold for the relationship between 25-OHD and diabetes risk, although there was a stronger decrease in risk within the higher range of 25-OHD concentration.
Moreover, the associations were consistent across most subgroup analyses. The exception was subgroups defined by BMI, in which the association was stronger among overweight/obese women than in normal-weight women (OR=0.46).
"To our knowledge, this study is the largest observational longitudinal study that used blood 25-OHD concentration to assess vitamin D status prior to development of Type 2 diabetes and the first one that reported such an association in a US cohort," write Pittas et al in the journal Diabetes Care.
They conclude: "Our findings suggest that raising 25-OHD concentration may be an effective strategy at reducing risk of incident type 2 diabetes in women."
They add: "Our results need to be confirmed in randomized controlled trials specifically designed to test such a hypothesis."
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By Joanna Lyford