By Avigayil Kadesh
Vitamin D deficiency and asthma are both common in the world population. Could there be any connection between the two? Scientists have been pondering this question over the past few years.
A recent study led by Dr. Ronit Confino-Cohen of the Allergy and Clinical Immunology Unit at Meir Medical Center in Kfar Saba, Israel, concludes that while one does not cause the other, too-low levels of vitamin D do seem to trigger more frequent asthma attacks in those who already have this lung condition.
According to the US Centers for Disease Control, 18.7 million American adults (8 percent) and 6.8 million American children (9%) have been diagnosed with asthma, a chronic disease marked by recurrent attacks of breathlessness and wheezing as the lining of the lungs’ bronchial tubes swells and narrows the airways. From 2001 to 2011, the number of Americans with asthma grew by 28%.
The overall prevalence rate of vitamin D deficiency reported in 2011 was 41.6%, and even higher among American blacks and Hispanics.
The Israeli study suggests that boosting vitamin D levels could help reduce the number of asthma flare-ups in those found to be deficient. "Vitamin D has significant immunomodulatory effects and, as such, was believed to have an effect on asthma - an immunologically mediated disease," said Confino-Cohen.
25% increase in attacks
Confino-Cohen and her fellow researchers came to their conclusion after analyzing the medical records of nearly four million members of Clalit Health Services, Israel's largest healthcare provider.
They zeroed in on 307,900 people between the ages of 22 to 50 who had been tested for vitamin D levels over the time period from 2008 and 2012. Then they identified those with asthma defined as “uncontrolled,” meaning they were prescribed at least five “rescue” inhalers, one prescription of oral corticosteroids or visited the doctor for asthma at least four times in a single year.
Confino-Cohen, who is on the faculty of Tel Aviv University’s school of medicine, said adults were chosen for this study because most of the existing data regarding vitamin D and asthma was gathered from children and was inconsistent.
For example, a 2012 study showed asthmatic children with low vitamin D levels have poorer lung function. However, the authors of that study acknowledged that there were conflicting results from previous research on this association.
“Our present study is unique,” said Confino-Cohen, “because the study population of young adults is very large and 'uncontaminated' by other diseases."
Among the Clalit patients with documented vitamin D status, 6.9% (21,237) had physician-diagnosed asthma versus 5.7% in the general population. And those with a vitamin D deficiency turned out to be 25 percent more likely than other asthmatics to have had at least one flare-up in the recent past.
Results of the study were published in October 2014 in the journal
Allergy by Confino-Cohen and her colleague Arnon Goldberg, with Becca Feldman and Ilan Brufman of the Clalit Research Institute.
Improving quality of life
The findings point to a need for measuring the vitamin D level of anyone diagnosed with asthma, and especially people whose asthma cannot be controlled with existing treatments.
The next question is how to take in sufficient vitamin D. Though 10 daily minutes out in the sunshine are sufficient, doctors concerned about skin cancer recommend instead getting the vitamin from supplements or from foods such as eggs, fatty fish, mushrooms or fortified dairy or plant-based milks.
Confino-Cohen noted that the incidence of asthma is steadily rising worldwide – an estimated 300 million people, according to the American Academy of Allergy, Asthma and Immunology – and experts cannot pinpoint exactly why.
She anticipates that further research will support her team’s findings “and open a new treatment modality to the population of uncontrolled asthmatics."
Said Confino-Cohen, "We know a lot about this disease, and many therapeutic options are available. So it's quite frustrating that the prevalence of asthma is not decreasing and many patients suffer exacerbations and significant impairment in their quality of life. Increasing Vitamin D levels is something we can easily do to improve patients' quality of life."