Vitamin D may not protect against asthma attacks after all, new findings suggest

LONDON — Vitamin D is one of the most important vitamins for our body, and it’s long been thought to reduce risk of asthma attacks. A new review suggests otherwise, however. According to the British medical research agency Cochrane, vitamin D supplements do not reduce the risk in children nor adults after all.

Previously, even Cochrane had released a review backing the notion that vitamin D was beneficial for asthmatics, but this newest one contrasts that.

“Vitamin D deficiency has been linked to an increased risk of severe asthma attacks and our previous Cochrane review, published in 2016, found that vitamin D reduced the risk of asthma attacks. However, more studies have been published since then and when we included the extra data in our updated review, the overall results changed. We found that vitamin D supplements had no effect on risk of asthma attacks or on control of asthma symptoms compared with a placebo,” says Adrian Martineau, Clinical Professor of Respiratory Infection and Immunity at Queen Mary University of London, who helped carry out the research.

Martineau and his team conducted their work by analyzing the results of 20 randomized controlled trials, which included data on 1,155 children and 1,070 adults with asthma. This review is significantly larger than their last one, which only included the results of nine trials and a total of 1,093 people. Most patients in both reviews didn’t suffer from severe asthma.

The team ultimately found no statistically significant differences in the amount of people experiencing asthma attacks requiring steroid treatment upon comparing those who took vitamin D supplements to patients who took a placebo medication. Even when people were vitamin D deficient, or were given different doses, no differences were noted. Similarly, age didn’t seem to be a defining factor either.

“We can’t be certain why this updated review has given a different result to our original study from 2016. It could be that people with asthma may be getting better treatment than previously. Or it could be that, in general, rates of vitamin D deficiency have decreased over time, due to increasing intake of supplements or fortified foods. Either of these factors could obscure potential benefits from taking vitamin D supplements. Regardless of the reason, these most recent findings are likely to be correct for people living with asthma today. This also highlights why it’s vital to update reviews when more research is published,” said Anne Williamson, the first author on the study who is also from Queen Mary University of London.

Interestingly, most studies chose to use cholecalciferol, which is the form of vitamin D that you’ll usually find in supplements. However, one trial that used calcidiol, which the body can generate from vitamin D and has been shown to raise levels more effectively, reported an improvement in asthma in those taking it.  In light of these findings, the researchers all agree that more work needs to be conducted to come to a more solid consensus on the role vitamin D plays in asthma, and especially which form of it.

The findings are published in the journal Cochrane Database of Systematic Reviews.

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Do not make any changes to your current dietary supplement or medical routine without first consulting your doctor.

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About the Author

Shyla Cadogan, RD

Shyla Cadogan is a DMV-Based acute care Registered Dietitian. She holds specialized interests in integrative nutrition and communicating nutrition concepts in a nuanced, approachable way.

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