A new Cochrane review says that taking vitamin D supplements does not lower the risk of asthma attacks in people.
This is different from what a previous Cochrane review found, which said that people who took vitamin D had fewer asthma attacks. But the review didn’t find anything bad about taking vitamin D and didn’t look into any other possible health benefits.
Researchers from the University of Edinburgh and the Queen Mary University of London conducted the review.
“Vitamin D deficiency has been linked to an increased risk of severe asthma attacks,” says Researcher Adrian Martineau, adding “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.”
They found that, compared to a placebo, vitamin D supplements had no effect on the risk of asthma attacks or the ability to control asthma symptoms.
The findings of 20 randomised controlled trials, the gold standard in medical research, were examined by Professor Martineau and his colleagues. The data included information on 1,155 children and 1,070 adults who had asthma. This is different from the last review, which used data from nine trials with a total of 1,093 people. Most of the study participants had mild to moderate asthma.
There was no statistically significant difference in the number of participants who had an asthma episode severe enough to need treatment with a course of steroid pills between the groups that were given either a vitamin D supplement or a placebo.
No benefit of vitamin D supplementation on asthma control was seen throughout the trials included in the meta-analysis, regardless of whether participants were vitamin D deficient when they enrolled, the amount of vitamin D administered, or the age of the participants.
“In contrast to our previous Cochrane review on this topic,” remarks Professor Martineau,” 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.
“We can’t be certain why this updated review has given a different result to our original study from 2016,” points out first author Anne Williamson.
According to the first author, “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.”
In comparison to the evaluation done in 2016, this one included data from twenty clinical studies, and the number of cases involving asthmatic children has increased since the last time this was done. In contrast to some earlier evaluations, the review team claims to have used tougher criteria for which papers would be included. For instance, studies that did not compare vitamin D with placebo or that did not keep track of patients for at least 12 weeks were omitted.
Patients using cholecalciferol, the most common type of vitamin D supplement, were the focus of the majority of the studies included in the meta-analysis. In one study, participants who took the supplement calcidiol, which the body can produce from vitamin D, had improved asthma control. According to the reviewers, further study is required to verify whether or not this particular kind of vitamin D is beneficial for persons who suffer from asthma.
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