Adults with asthma who have vitamin D deficiency may be much more likely to experience asthma attacks. This is according to a new study by researchers from Tel Aviv University in Israel.

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Researchers found that asthmatics with vitamin D deficiency were 25% more likely to experience an asthma attack than those with normal vitamin D levels.

This is not the first study to link vitamin D deficiency with asthma severity. In 2012, Medical News Today reported on a study claiming asthmatic children with low vitamin D levels have poorer lung function. But the authors of this latest study say previous research suggesting such associations has been conflicting.

"Vitamin D has significant immunomodulatory effects and, as such, was believed to have an effect on asthma - an immunologically mediated disease," notes study author Dr. Ronit Confino-Cohen, of the Sackler Faculty of Medicine at Tel Aviv University.

"But most of the existing data regarding vitamin D and asthma came from the pediatric population and was inconsistent," he adds. "Our present study is unique because the study population of young adults is very large and 'uncontaminated' by other diseases."

Vitamin D-deficient asthmatics '25% more likely to have an asthma attack'

The research team assessed the medical records of almost 4 million individuals aged 22-50 who were members of Clalit Health Services - the largest health care provider in Israel.

The vitamin D levels of 307,900 individuals were measured. Among these, 21,237 people had physician-diagnosed asthma.

Results of the analysis, recently published in the journal Allergy, revealed that asthmatics who had low vitamin D levels were 25% more likely to have an asthma attack than those whose vitamin D levels were normal.

These findings remained even after the team accounted for other risk factors for asthma, such as obesity, smoking and co-existing chronic illnesses.

Commenting on the team's findings, Dr. Confino-Cohen says:

"Our results add more evidence to the link between vitamin D and asthma, suggesting beneficial effects of vitamin D on asthma exacerbations.

We expect that further prospective studies will support our results. In the meantime, our results support a recommendation for screening of vitamin D levels in the subgroup of asthma patients who experience recurrent exacerbations. In those with vitamin D deficiency, supplementation may be necessary."

Vitamin D supplementation: can it really help treat asthma?

But whether vitamin D supplements are effective for symptoms of asthma is debatable. Earlier this year, MNT reported on a study published in JAMA, in which researchers claimed that for people with asthma, vitamin D supplements do not improve symptoms or treatment.

"In adults with persistent asthma and lower vitamin D levels, treatment with vitamin D3 did not reduce the rate of first treatment failure or exacerbation. These findings do not support a strategy of therapeutic vitamin D3 supplementation in patients with symptomatic asthma," the researchers of that study wrote.

The team involved in this latest study, however, suggest the opposite, noting that it is "frustrating" that prevalence of asthma is not declining when so much is known about how to treat the illness and reduce its effects on patients' lives. "Increasing vitamin D levels is something we can easily do to improve patients' quality of life," adds Dr. Confino-Cohen.

MNT recently reported on a study suggesting that vitamin D deficiency may increase the risk of poor brain function among patients who have been resuscitated after sudden cardiac arrest.