provides evidence for a link between vitamin D insufficiency and asthma
severity.
vitamin D in more than 600 Costa Rican children were inversely linked to several
indicators of allergy and asthma severity, including hospitalizations for
asthma, use of inhaled steroids and total IgE levels, according to a study that
will appear in the first issue for May of the American Journal of
Respiratory and Critical Care Medicine.
suggested that vitamin D may affect how airway cells respond to treatment with
inhaled steroids, this is the first in vivo study of vitamin D and disease
severity in children with asthma.
Juan Celedón, M.D., Dr. P.H. and Augusto
Litonjua, M.D., M.P.H. of Harvard Medical School and colleagues recruited 616
children with asthma living in the Central Valley of Costa Rica, a country known
to have a high prevalence of asthma. Each child was assessed for allergic
markers, including both allergen-specific and general sensitivity tests, and
assessed for lung function and circulating vitamin D levels. Children whose
forced expiratory volume in one second (FEV1) exceeded 65 percent of
the predicted value were also tested for airway reactivity.
They found
that children with lower vitamin D levels were significantly more likely to have
been hospitalized for asthma in the previous year, tended to have airways with
increased hyperreactivity and were likely to have used more inhaled
corticosteroids, all signifying higher asthma severity. These children were also
significantly more likely to have several markers of allergy, including
dust-mite sensitivity.
“To our knowledge this is the first study to
demonstrate an inverse association between circulating levels of vitamin D and
markers of asthma severity and allergy,” wrote Drs. Celedón and Litonjua “While
it is difficult to establish causation in a cross-sectional study such as this,
the results were robust even after controlling for markers of baseline asthma
severity.”
suggests that there may be added health benefits to vitamin D supplementation”
said Dr. Celedón. Current recommendations for optimal vitamin D levels geared
toward preserving bone health, such as preventing rickets in children and
osteoporosis in adults.
provides epidemiological support for a growing body of in vitroevidence that
vitamin D insufficiency may worsen asthma severity, and we suspect that giving
vitamin D supplements to asthma patients who are deficient may help with their
asthma control” wrote Drs. Celedón and Litonjua, noting that a clinical trial
should be the next step in this research. “Whether vitamin D supplementation can
prevent the development of asthma in very young children is a separate question,
which will be answered by clinical trials that are getting under way,” he
said.
that vitamin D, unlike most other nutrients, is primarily synthesized in the
body rather than consumed. Because about 90 percent of circulating vitamin D is
produced by the body in response to sun exposure, deficiency is often related to
behavioral issues rather than an inadequate dietary intake. Increased time spent
indoors, increased use of sunscreen and sun-protective clothing all lead to
decreased levels of vitamin D. Dietary sources of vitamin D, primarily fortified
foods and fatty fish or fish oils, and vitamin D in current multivitamin
preparations are unlikely to make up the deficiency.
is only by investigating the effects of vitamin D in doses at, and above, those
currently recommended that decisions can be made on the optimal intake of
vitamin D and the possible prevention and treatment of asthma,” wrote Graham
Devereux, M.D., of the Department of Environmental and Occupational Medicine at
the University of Aberdeen in the accompanying editorial in the same issue of
the journal.