Widespread Vitamin D devidiency may be cause of post-Winter FLU outbreaks

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http://www.newstarget.com/021229.html

 

Widespread vitamin D deficiency may be cause of post-Winter flu outbreaks,

scientists suggest

Friday, December 01, 2006 by: Ben Kage

 

(NewsTarget) A team of researchers is gathering data in an attempt to

determine why flu outbreaks hit the Northern Hemisphere during winter months

and

tend to peak between December and March, and a new theory suggests it may be a

lack of sunshine-produced vitamin D.

 

In the past, many theories have been put forward to explain the seasonal flu

flux, but explanations such as cold air and the tendency of people to group

together " remain astonishingly superficial and full of inconsistencies, " said

Dr. Scott Dowell, director of the Global Disease Protection Program at the

Centers for Disease Control and Prevention in Atlanta.

 

Theories about a chill causing the disease's prevalence is upended by

evidence from tropical locations, where flu remains common and follows a

similar

seasonal pattern to its cold-climate counterpart. The grouping theory is

debunked by the fact that certain groups of people are stuck in small spaces

together year round, with no greater likelihood of contracting flu than anyone

else.

 

Now, the Harvard-University-led team is investigating whether inadequate sun

exposure during the winter may open people up to infection, since exposure

to ultraviolet B radiation (UVB) radiation from the sun causes vitamin D

production in the skin. If the lack of vitamin D and increased flu cases in the

winter are connected, it could have a significant impact on public health, as

an average of 36,000 people die from flu in the United States every winter,

primarily the elderly or the very young.

 

R. Edgar Hope-Simpson published the first paper that identified a link

between flu epidemics and the winter solstice -- usually indentified as the

start

of winter and the shortest day of the year -- in 1981, despite having no

formal training in the field of epidemiology. Simpson noted that flu infections

spiked just before and after the winter solstice, and theorized that solar

radiation might cause a sort of " seasonal stimulus " in the virus, the host or

both, although he could not identify the stimulus.

 

Simpson's work was largely ignored, according to Dr. John Cannell, a

psychiatrist at the Atascadero State Hospital in California. However, Cannel

and his

Harvard colleagues suggest the stimulus to which Simpson referred may be

vitamin D. Cannell began investigating the possibility when a flu outbreak hit

Atascadero in April of 2005 and all the wards surrounding his were infected,

Cannell's patients were not. All of his patients, he said, were taking high

daily doses of vitamin D.

 

During the winter, people are outdoors less often and the skin has less

opportunity to produce vitamin D, and the atmosphere during that season is

adept

at blocking UVB radiation. This is why some health experts warn that

Americans may not be getting sufficient vitamin D, especially with the

resurgence of

the vitamin-deficiency-related bone disorder known as rickets.

 

In the report -- published in the December issue of Epidemiology and

Infection -- the researchers posit that the vitamin D stimulated by sunlight

may, in

turn, cause the body to produce the infection-fighting peptide cathelcidin.

No studies been conducted that to show whether cathelcidin effects influenza,

but previous studies in the March issue of Science have shown it attacks a

range of fungi, viruses and bacteria, including the bacteria that causes

tuberculosis.

 

The tropical evidence that upsets the chill theory does not preclude the

vitamin D theory, as Cannell and colleagues point out, as studies show that

vitamin D deficiencies have even been recorded in equatorial locations.

Additionally, a 2003 analysis of flu cases found they were greatest during the

rainy

season, when there is a significant cloud cover and reduced sun exposure.

 

Despite the evidence offered by Cannell and colleagues, some members of the

scientific community remain skeptical about the theory.

 

" They have manipulated the literature -- some of it very bad literature --

to prove their points, " said Dr. James Cherry, a pediatric infectious disease

specialist at UCLA's David Geffen School of Medicine. However, he added, " The

hypothesis should be easy to prove or disprove with a controlled, blinded

study. "

 

Cannell, for his part, said he takes more than twice the recommended daily

dose of vitamin D during winter months and reports he rarely gets sick.

 

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