In a study from the Queen Mary University of London and elsewhere, scientists found that taking vitamin D supplements does not reduce the risk of asthma attacks in children or adults.
These findings are in contrast to a previous Cochrane Review that indicated a reduction in asthma attacks in people taking vitamin D.
However, the review found no harm in taking vitamin D and it did not examine other possible health benefits.
Vitamin D deficiency has been linked to an increased risk of severe asthma attacks.A previous review found that vitamin D reduced the risk of asthma attacks.
In the current study, the team found that vitamin D supplements had no effect on the risk of asthma attacks or on the control of asthma symptoms compared with a placebo.
They analyzed the results of 20 randomized controlled trials—the gold standard for medical research—including data on 1,155 children and 1,070 adults with asthma.
This compares to nine trials involving a total of 1,093 people whose data contributed to the previous review. Most patients in the trials had mild to moderate asthma.
When the team compared patients who were assigned to take a vitamin D supplement with patients who were assigned to take a placebo (dummy medication), they found no strong difference in the number of people who experienced an asthma attack requiring treatment with a course of steroid tablets.
The review did not find any effect of taking vitamin D on asthma control even when people were vitamin D-deficient when they joined the studies, or with different doses of the supplement, or in people of different ages.
The team says the trials they looked at did not include many people with severe asthma or people with very low levels of vitamin D in their blood, so these are areas where more research is still needed.
Most of the trials included in the review involved patients taking cholecalciferol, which is the typical form of vitamin D supplement.
One trial that used calcidiol, which is a compound that the body can make from vitamin D, reported an improvement in asthma control in patients taking this supplement.
The reviewers say further research is needed to confirm whether this form of vitamin D has benefits for people with asthma.
If you care about asthma, please read studies about a new way to make asthma drugs last longer, and scientists find more post-COVID-19 lung damage.
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The study was conducted by Adrian Martineau et al and published in the journal Cochrane Database of Systematic Reviews.
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