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 Previous research had linked low vitamin D levels to
more asthma-related problems, like weaker lungs and more asthma
exacerbations.
But it wasn’t clear if vitamin deficiencies were causing those
problems, or if giving patients extra vitamin D was the answer.
Lead author Dr. Mario Castro from Washington University School of
Medicine in St. Louis, Missouri, said as many as two-thirds of his
asthma patients are lacking in vitamin D.
“Our thought was that vitamin D would potentially make . . . the
standard therapy, inhaled corticosteroids, work better in these
patients, and that it would reduce their asthma exacerbations,” he
told Reuters Health.
To test that theory, the researchers studied just over 400 adults
with asthma and low vitamin D levels. They randomly assigned half of
the participants to take vitamin D3 supplements every day, and the
other half to take a vitamin-free placebo pill.
All of the patients also took corticosteroids to help keep their
asthma in check.
Over the next six months, Castro and his team tracked so-called
treatment failures - the times patients were sent to the emergency
room or hospitalized for asthma, had declines in lung function or
had to increase their use of asthma medication.
They found between one-quarter and one-third of participants in both
the vitamin D and placebo groups had a treatment failure during the
study. The only benefit linked to vitamin D was that patients in the
vitamin group needed slightly lower doses of corticosteroids to
control their asthma.
When the researchers looked only at patients whose vitamin D levels
significantly improved from the supplements, they found benefits in
some areas compared to the placebo group - such as fewer patients
with an asthma exacerbation - but not in other areas.
The findings don’t support using vitamin D as a general treatment
strategy for people struggling with asthma symptoms, the authors
write in the Journal of the American Medical Association. They also
presented their results Sunday at the American Thoracic Society
International Conference in San Diego.
Castro said he thinks it is still appropriate to treat some asthma
patients with vitamin D while more research is being conducted. He
prescribes it to people with low vitamin D levels who also have
uncontrolled asthma symptoms, and monitors them to make sure their
levels come up.
“I think there may be some benefit, and vitamin D is inexpensive and
has (minimal) side effects,” he said.
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Vitamin D3 supplements cost a few dollars per month for the dose
used for most of the study, about 4,000 international units.
Dr. Ken Kunisaki from the University of Minnesota in Minneapolis
said there are still some questions, such as what is a big enough
dose of vitamin D to give people who are deficient.
But he said that in general, the new findings were “disappointing.”
Regarding the role of vitamin D in asthma, “It’s been a fairly
consistent story from the observational studies,” Kunisaki, who
specializes in pulmonary and critical care medicine, told Reuters
Health.
Those studies relied on measuring people’s vitamin D levels and
asthma symptoms, rather than instructing some patients to take extra
vitamin D. In observational studies, it’s possible another
underlying factor could explain the link between low vitamin D and
asthma-related problems, he said.
“It goes to show why we do randomized clinical trials,” said
Kunisaki, who wasn’t involved in the new research.
“This study would say that at least in this population, there’s no
role for routinely looking at vitamin D levels, at least for
asthma-control purposes," he concluded.
The study was funded by the National Institutes of Health, and the
asthma medications used were provided free of charge by their
manufacturer, Sunovion Pharmaceuticals.
SOURCE: http://bit.ly/Tm0zFL
Journal of the American Medical Association, online May 18, 2014.
[© 2014 Thomson Reuters. All rights
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