February 6, 2023

expert reaction to study looking at vitamin D supplementation and reduction in diabetes risk

A study published in Annals of Internal Medicine looks at vitamin D and risk for type 2 diabetes in people with prediabetes.

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“The study is interesting but given the results show borderline significance for lower diabetes risk is only evident with data from three trials combined, this could easily be a chance finding.  I would like to see a larger and longer trial to confirm.  Even if confirmed, the likely degree of benefit may only be around ¼ of that seen with lifestyle intervention in trials.  Hence, I would not use or promote vitamin D to prevent diabetes in those with pre-diabetes on the basis of this evidence.  Rather, helping people to improve diets and walk a little more has more evidence to promote it to prevent diabetes and improve other outcomes, which vitamin D supplementation does not.”    

Dr Katarina Kos, Senior Lecturer in Diabetes and Obesity, University of Exeter, said:

“Vitamin D is a fat-soluble vitamin. Measurement of blood levels thus depend on body fat content. This analysis has appreciated baseline body mass index (BMI) and concluded that those who had maintained higher blood levels of vitamin D and were of lower BMI were more likely to normalize their glucose metabolism. Any weight loss during the trial which is a key determinant of (pre-) diabetes remission was not assessed in the analysis. The National Diabetes Prevention Trial showed that people with prediabetes who lose 5% of weigh and increase physical activity reverse the risk of developing diabetes by 58%.

“Findings of the three individual studies which were pooled together in this analysis did not show a significant benefit of Vitamin D supplementation per se. Thus, whilst evidence of actual Vitamin D benefits independent of weight loss are yet limited, one should be careful not be distracted by Vitamin D supplementation and Vitamin D blood levels (which naturally increase after weight loss) and keep in mind the primary importance of lifestyle change.”

‘Vitamin D and Risk for Type 2 Diabetes in People With Prediabetes: A Systematic Review and Meta-analysis of Individual Participant Data From 3 Randomized Clinical Trials’ by Anastassios G. Pittas et al. was published in Annals of Internal Medicine at 22:00 UK time Monday 6 February 2023.

DOI: 10.7326/M22-3018

Declared interests

Prof Naveed Sattar: “No conflicts of interest.”

Dr Katarina Kos: “I have no conflict of interest.”