Epidemiol Infect. 2006 Sep 7;:1-12 [Epub ahead of print]
"Epidemic influenza and vitamin D."
Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S,
Garland CF, Giovannucci E.
"In 1981, R. Edgar Hope-Simpson proposed that a 'seasonal stimulus'
intimately associated with solar radiation explained the remarkable
seasonality of epidemic influenza. Solar radiation triggers robust
seasonal vitamin D production in the skin; vitamin D deficiency is
common in the winter, and activated vitamin D, 1,25(OH)2D, a steroid
hormone, has profound effects on human immunity. 1,25(OH)2D acts as
an immune system modulator, preventing excessive expression of
inflammatory cytokines and increasing the 'oxidative burst' potential
of macrophages. Perhaps most importantly, it dramatically stimulates
the expression of potent anti-microbial peptides, which exist in
neutrophils, monocytes, natural killer cells, and in epithelial cells
lining the respiratory tract where they play a major role in
protecting the lung from infection. Volunteers inoculated with live
attenuated influenza virus are more likely to develop fever and
serological evidence of an immune response in the winter. Vitamin D
deficiency predisposes children to respiratory infections.
Ultraviolet radiation (either from artificial sources or from
sunlight) reduces the incidence of viral respiratory infections, as
does cod liver oil (which contains vitamin D). An interventional
study showed that vitamin D reduces the incidence of respiratory
infections in children. We conclude that vitamin D, or lack of it,
may be Hope-Simpson' s 'seasonal stimulus'."
PMID: 16959053
A more through account by the leading author
http://www.medicalne...hp?newsid=51913
