Followup: vitamin D and diabetes
Quite some time ago, I wrote about a story on vitamin D and diabetes:
A: Someone needs to do a randomized trial, where half the participants get vitamin D and half get a dummy pill. If the effect is real, fewer people getting vitamin D will end up with diabetes.
Q: That sounds like a good idea. Is someone doing a trial?
A: Yes, Professor Peter Ebeling, of the the University of Melbourne.
Q: Is there some useful website where I can find more information about the trial?
A: Indeed.
Q: Will it work?
A: No.
Q: Are you sure?
A: No, that’s why we need the trial.[…]
While the clinical trial registry hasn’t been updated, there are now published results from this trial. The researchers didn’t get to their planned 160 participants; they gave up at 95 because of slow recruitment. Even so, if the results had been as dramatic as in the observational studies, they would have been able to see the benefit.
They didn’t:
In this 6-month RCT of vitamin D and calcium supplementation in which over 90% of the participants reached the target serum 25(OH)D concentration of 75 nmol/L, there was no effect of supplementation on any measure of insulin sensitivity, insulin secretion or β-cell function in multi-ethnic vitamin D-deficient individuals at risk of type 2 diabetes (with prediabetes or an AUSDRISK score ≥15).
These results are no fun, so they have not received the same media attention as the observational correlations that prompted the trial, even though they are more reliable and more relevant to individual health choices.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »