Cochrane Review: Vitamin D Supplements Do Not Reduce Risk of Asthma Attacks


The new findings, which include updated data, contradict results of a previous analysis by the same investigators.

Taking vitamin D supplements does not reduce the risk of asthma attacks in adults or children, according to an updated Cochrane review.

The findings contradict results of a previous Cochrane review that indicated a reduction in asthma attacks in individuals taking vitamin D. However, the review found no harm in taking vitamin D supplements.

“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,” Adrian Martineau, PhD, a clinical professor of Respiratory Infection and Immunity at Queen Mary University of London, said in a statement.

“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,” Martineau said.

Investigators analyzed the results of 20 randomized controlled trials, which included data on 1155 children and 1070 adults with asthma. In the previous review, investigators included 9 trials with a total of 1093 individuals.

Most individuals in the trials had mild to moderate asthma.

Individuals who were assigned to take a vitamin D supplement and those who were assigned to take a placebo had no statistically significant difference in the number who experienced an asthma attack requiring treatment with a course of steroid tablets.

Additionally, the individuals did not find any effect of taking vitamin D on asthma control, even in those of different ages and when participants who were vitamin D deficient joint the study and were given different doses of the supplement.

“In contrast to our previous Cochrane review on this topic, this updated review does not find that vitamin D offers protection against asthma attacks or improves control of asthma symptoms. However, the trials we 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,” Martineau said.

Investigators noted that they applied stricter criteria on which studies would be included in this study compared with the previous review. For example, they excluded studies that did not compare vitamin D with a placebo and those that did not monitor individuals for at least 12 weeks.

Most of the trials included in the review included individuals who were taking cholecalciferol, which is a typical form of vitamin D supplement. Results of another trial in the study included calcidiol, which is a compound that the body can make from vitamin D, showed an improvement in asthma control in individuals taking this supplement.

Further research is needed to confirm whether calcidiol has benefits for individuals with asthma, investigators said.


Cochrane Review finds that vitamin D does not reduce risk of asthma attacks. EurekAlert. News release. February 5, 2023. Accessed February 8, 2023.

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