A wide-ranging review of clinical trial data, which involved research from the University of Aberdeen, has found that the use of vitamin D to lower blood pressure is ineffective.
Aberdeen researchers were part of a global consortium led by the University of Dundee which analysed clinical trial data and individual patient data with regard to vitamin D supplementation and blood pressure.
In an article published online by JAMA Internal Medicine the research team conclude that vitamin D should not be used to treat hypertension or to lower blood pressure.
Intervention studies have produced conflicting evidence on the blood pressure-lowering effect of vitamin D. An increasing number of clinical trials of have studied vitamin D and cardiovascular health, according to the study background.
Professor Helen Macdonald from the University of Aberdeen worked in a global team involving collaborators from the University of Aberdeen and Cambridge University Hospitals NHS Trust in the UK, Australia, New Zealand, India, USA and Europe which looked at 46 trials where vitamin D had been used to try and lower blood pressure (4,541 participants) and individual patient data were obtained for 27 trials (3,092 participants).
In both clinical trial and individual patient data, no effect of vitamin D supplementation was seen on systolic blood pressure or diastolic blood pressure.
Dr Miles Witham from the University of Dundee said: “Large studies have shown that people with low vitamin D levels tend to have higher blood pressure. It hasn’t been clear though whether giving vitamin D to people actually lowers their blood pressure as individual trials have been too small to find out the answer.
“By combining all of these trials into one analysis, we have been able to show that taking vitamin D supplements doesn’t lower your blood pressure – even if you start with low vitamin D levels or a high blood pressure.
“This is important as blood pressure is one of the things that people had thought vitamin D might be used for and there are some practitioners who already suggest that patients with high blood pressure should take vitamin D.
“Our work shows that this doesn’t work, and so vitamin D cannot be recommended as a way to help control high blood pressure. Vitamin D can help reduce falls and fractures in older people, and might still have other health benefits, but we need to wait for the result from further large clinical trials before we know if more widespread use of this medication is safe or worthwhile.”
Professor Helen Macdonald said: “The original Aberdeen study which was included in this combined analysis found a seasonal change in blood pressure, with higher mean blood pressure in the winter, going down in the summer and back up again in the winter. As this was independent of the treatment group or placebo, it shows that vitamin D itself was not the reason for the drop in blood pressure in summer. The analysis of this combined dataset from a number of studies adds more evidence to support that finding.”