Numerous observational studies – the type of research where a group of people is observed, but not randomised to different treatments – have suggested a relationship between low levels of Vitamin D and strokes or heart attacks.

It’s prompted many people to seek out Vitamin D supplementation in the belief it will help their heart and vascular health. But in observational trials it’s difficult to control for confounding factors – unforeseen things that might influence the study results, like a person’s diet or fitness.

To try and pin down what’s going on in a more rigorous way, US researchers conducted a meta-analysis – collecting information from many studies and synthesising it to see where the weight of evidence lies.

And they didn’t use observational studies, but randomised clinical trials – gold standard evidence that compares, in this case, groups of people who were given vitamin D supplements versus people who were given placebos.

The researchers were able to collect 21 of these trials, involving more than 80,000 people. The studies had to have looked at vitamin D supplementation over more than a year.

They also had to have tracked ‘major adverse cardiac events’ – heart attacks, strokes and death from other cardiovascular disease.

When considering those who got supplements versus those who received placebo side-by-side, there was no significant difference in the number of heart-related events experienced by either group, suggesting the supplementation made no difference at all.

Implications

Vitamin D supplements don’t seem to be effective in protecting heart health, and if you’re taking them for that purpose you may like to consult with your doctor about other options.

Vitamin D deficiency does happen in Australia, but you can usually get your recommended daily intake of the substance by walking in moderate sunlight for up to 15 minutes a day with your arms exposed.

Groups especially at risk of vitamin D deficiency include people with very dark skin, older Australians who don’t spend time outdoors, and people who cover their skin for cultural or religious reasons.

Last Reviewed: 16/04/2020

© Norman Swan Medical Communications.



References

For reference: Barbarawi, et al (2019). Vitamin D Supplementation and Cardiovascular Disease Risks in More Than 83 000 Individuals in 21 Randomized Clinical Trials. JAMA Cardiology doi: 10.1001/jamacardio.2019.1870.

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