Asthma is a common chronic disease affecting about 300 million
people worldwide. The symptoms of asthma include wheezing, coughing,
chest tightness and shortness of breath.
Low blood levels of vitamin D have been linked to increased risk of
asthma attacks in children and adults with asthma. There has been a
growing interest in the potential role of vitamin D in asthma management
because it might help to reduce upper respiratory infections, (such as
the common cold) that can lead to exacerbations of asthma.
‘Taking an oral vitamin D supplement in addition to standard asthma medication is likely to reduce severe asthma attacks.’
clinical trials have tested whether taking vitamin D as a supplement has
an effect on asthma attacks, symptoms and lung function in children and
adults with asthma.
A recent Cochrane Review
has found evidence from randomized
trials, that taking an oral vitamin D supplement in addition to standard
asthma medication is likely to reduce severe asthma attacks.
The team of Cochrane researchers found seven trials involving 435
children and two studies, involving 658 adults. The study participants
were ethnically diverse, reflecting the broad range of global geographic
settings, involving Canada, India, Japan, Poland, the UK, and the U.S.
The majority of people recruited to the studies had mild to moderate
asthma, and a minority had severe asthma. Most people continued to take
their usual asthma medication while participating in the studies. The
studies lasted for between six and 12 months
The researchers found that giving an oral vitamin D supplement
reduced the risk of severe asthma attacks requiring hospital admission
or emergency department attendance from 6% to around 3%. They also found
that vitamin D supplementation reduced the rate of asthma attacks
needing treatment with steroid tablets.
These results are based largely
on trials in adults. They also found that vitamin D did not improve lung
function or day-to-day asthma symptoms, and that it did not increase
the risk of side effects at the doses that were tested.
The Cochrane Review
's lead author, Professor Adrian
Martineau from the Asthma UK Center for Applied Research, Queen Mary
University of London, said, "We found that taking a vitamin D supplement
in addition to standard asthma treatment significantly reduced the risk
of severe asthma attached, without causing side effects."
He added, "This is an exciting result, but some caution is
warranted. First, the findings relating to severe asthma attacks come
from just three trials: most of the patients enrolled in these studies
were adults with mild or moderate asthma. Further vitamin D trials in
children and in adults with severe asthma are needed to find out whether
these patient groups will also benefit. Second, it is not yet clear
whether vitamin D supplements can reduce risk of severe asthma attacks
in all patients, or whether this effect is just seen in those who have
low vitamin D levels to start with. Further analyses to investigate this
questions are on-going, and results should be available in the next few