Newsgroup: it.salute.alimentazione
Titolo: [OT]Il vero motivo per cui l'influenza colpisce in inverno e come prevenirla naturalmente

Buona giornata a tutti gli amici del NG.
Vorrei invitarvi a leggere questo articoletto 
http://www.disinformazione.it/influenza_vero_motivo.htm
 e a dirmi cosa ne 
pensate voi...Quanto c'è di vero e quanto no?
Io sono un pò scettica...
A presto! 
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 Io sono un pň scettica...
Anch'io. Quel sito in genere tiene fede al suo nome, "disinformazione" ;-)
In ogni caso, il rischio di un deficit di vit. D potrebbe riguardare Paesi
ben piů a nord dell'Italia, dove salvo casi particolari l'esposizione
solare non manca, mi pare, se si sta almeno un po' all'aria aperta e non
troppo tappati in casa o in ufficio!
Tieni anche conto che l'organismo puň fare scorta di vit. D nei mesi
estivi...
"La vitamina D puň essere sintetizzata ed accumulata nei mesi estivi cosě
da mantenere un adeguato livello circolante di 1,25-(OH)2-D anche nei mesi
invernali."
http://www.sinu.it/larn/vit_lipo.asp#D
 

 pensate voi...Quanto c'è di vero e quanto no?
Non lo so!
Pensavo che la quantita' consigliata 3000 I.U. fosse davvero alta, ma
sembra che in Canada un bicchiere di latte fortificato con vitamina D
ne contenga 400 I.U., ce ne vogliono solo 7 bicchieri per arrivare a
quasi 3000.
Bah, mi pare cmq tanto, visto anche che viene immagazzinata nel corpo,
bisognerebbe chiedere a un dottore, perche' tra un'intossicazione e
un'influenza non ci vedo tutta questa differenza.
Una cosa e' certa, questo articolo mi ha fatto notare il fatto che
quest'inverno ho preso la vitamina D (perle di olio di fegato di un
pesce), e l'influenza non l'ho presa.
Chi lo sa!
Dovrebbero fare uno studio con placebo e tutti i crismi.

 ne contenga 400 I.U.,
Canada -> Nord -> poco sole -> poca produzione di vit D nell'organismo
Italia -> Paese do' Sole ;-) -> buona produzione di vit D nell'organismo

 wrote:

ma che c'entra! io semplicemente non so se 3000 I.U. sono troppi a
prescindere da dove sei, dalla stagione, da quanta luce prendi, da
quanto scura e' la tua pelle ( Italiano -> mediterraneo pelle scura ->
poca produzione di vit D nell'organismo ) eccetera.
Ho cercato in rete, c'e' chi vuole alzare la soglia RDA da 200 I.U. a
1000 I.U. e chi a 2000 I.U., che significa che allora 3000 I.U. non e'
cosi' esageratamente alta come sembrava.
Integratori di vitamina D ne trovi da 200 I.U., un latte canadese al
bicchiere 400 I.U., non so se mi spiego, forse a me fara' strano
perche' bevo latte in quantita' industriale (che gia' di suo ha
vitamina D).
Anche perche' ripeto, stando alla letteratura che si trova in giro non
e' difficile intossicarsi, e l'intossicazione puo' essere grave.

 pensate voi...Quanto c'è di vero e quanto no?
Riporto un articolo giornalistico che parla di questa teoria, che comunque 
resta un'ipotesi... 
Michael Stroh, "Theory suggests that a shortage of vitamin D triggers
outbreaks of flu", Baltimore Sun, November 26, 2006,
Link:
http://www.baltimoresun.com/news/health/bal-te.flu26nov26,0,3590649.story?coll=bal-nationworld-headlines
As the annual flu season looms, some scientists have this question on
their minds: Why now?
For more than a century, physicians have recognized that influenza
sweeps the Northern Hemisphere during the winter months, typically
peaking here between late December and March.
Over the years they've floated numerous theories to explain the
seasonal flu spike - blaming everything from the flood of frigid air to
the wintertime tendency of people to huddle indoors.
Yet these explanations "remain astonishingly superficial and full of
inconsistencies," says Dr. Scott Dowell, director of the Global Disease
Protection Program at the Centers for Disease Control and Prevention in
Atlanta.
Now Dowell and other researchers are focusing on a provocative new
hypothesis that blames annual flu epidemics on something most people
don't get enough of this time of year: sunshine.
In a paper scheduled for publication next month in the journal
Epidemiology and Infection, a Harvard University-led team proposes that
a vitamin D deficiency caused by inadequate winter sun exposure may
predispose people to infection.
If this theory proves correct, it would not only solve a long-standing
mystery, but could also have major public health consequences.
Influenza kills an average 36,000 people in the U.S. each winter,
mostly the very old and very young. If scientists could pinpoint the
secret behind its seasonal recurrence and somehow alter it, "the
potential impact would be far greater than the current influenza
vaccine," says Dowell.
Hippocrates, the Greek physician widely regarded as the father of
medicine, was the first to recognize that certain diseases ebb and flow
with the calendar. "Whoever wishes to investigate medicine properly,"
he wrote around 400 B.C., "should ... consider the seasons of the
year."
Epidemiologists, however, have found that this is easier said than
done.
"You look at the environment around you and say, 'What's the difference
between winter and summer?'" says Dr. David Fisman of the Ontario
Provincial Public Health Laboratory in Canada. "There are so many
things that are seasonal, it's really hard to tease them apart."
One obvious answer is that it's colder in winter. And for as long as
parents have bundled up their babies, there's been an unshakable belief
that catching a chill makes a person more susceptible to cold or flu.
Cold flunks tests Since World War II, scientists have devised numerous
teeth-chattering tests of this stubborn wives' tale, dunking volunteers
in cold baths or confining them to refrigerated meat lockers while
squirting virus-spiked mucus up their noses.
"All attempts at demonstrating some relationship between cold exposure
and susceptibility to infection have proved negative," Ron Eccles,
director of the Common Cold Centre at Cardiff University in Wales,
concluded in a recent published review of such studies.
Experiments on the influenza virus have hinted that the flu bug is more
stable in the cool, dry air of winter. But that doesn't solve the
mystery, says Fisman, whose summary of efforts to understand seasonal
influenza is scheduled for publication next year in the Annual Review
of Public Health.    
One reason: Influenza surveillance efforts in Southeast Asia and other
steamy tropical locales reveal that flu is not only common there but
also exhibits seasonal patterns akin to those in colder climates.
"If you go back to the hypothesis about cold temperature and flu, it
doesn't hold for the tropics," says epidemiologist Cecile Viboud of the
National Institutes of Health's Fogarty International Center in
Bethesda.
Then there's the crowding theory.
Because scientists think that the flu spreads only from person to
person, most have assumed that the disease ravages in winter because
people are cooped up in close quarters.
But even Sir Christopher Andrewes, the British virologist who
co-discovered the influenza virus in 1933, once observed, "I have
always had my doubts about this."
Andrewes, who died in 1988, argued that the winter crowding explanation
defies common sense, since office and factory workers are stuck indoors
year-round. And summertime flu epidemics remain rare despite the
prevalence of cruise ships, airplanes, and subways packed with
international travelers, other skeptics of the theory note.
"There are plenty of things that don't fit," says the CDC's Dowell.
The latest theory to generate a buzz centers on sunlight.
In 1981, a British general practitioner named R. Edgar Hope-Simpson
published the first paper documenting a link between influenza
epidemics in the northern hemisphere and the winter solstice.
The solstice - which arrives on Dec. 21 this year - is commonly
identified with the start of winter and is the shortest day of the
year.
Hope-Simpson, who had no formal training in epidemiology, realized that
influenza infections tended to jump just before and after the solstice.
Solar radiation, he surmised, triggered some sort of "seasonal
stimulus" that affected the flu virus, its human host or both.
Although he had no idea what that seasonal stimulus was, Hope-Simpson
believed that solving the mystery "would provide the key to
understanding most of the influenza problems confronting us."
"His work was basically ignored," says Dr. John Cannell, a psychiatrist
at the Atascadero State Hospital in California.
In their forthcoming paper in Epidemiology and Infection, Cannell and
colleagues from Harvard University, the National Institutes of Health
and Boston University propose that Hope-Simpson's seasonal stimulus
could be vitamin D.
The tip-off, says Cannell, came in April 2005, when an outbreak of
influenza swept through Atascadero, a maximum-security facility for the
criminally insane 200 miles south of San Francisco.
"The ward below me got it, then the ward to my right, to my left and
the one across the hall," he recalls.
Cannell's 32 patients, however, were spared.
As far as he could tell, there was only one glaring difference between
his patients and those who came down with flu: Cannell's patients were
taking high daily doses of vitamin D.
Manufactured by the skin in response to solar ultraviolet B radiation
(UVB), vitamin D is the only vitamin made naturally in the body.
On sunny days, a fair-skinned person can crank out the equivalent of
20,000 international units (IU) of the vitamin in 15 minutes, says
Cannell. One cup of fortified milk, by contrast, contains fewer than
100 IU.
But vitamin D production plummets during winter because people spend
less time outdoors and because UVB radiation has a harder time
penetrating the atmosphere in that season, especially at middle to high
latitudes.
As a result, health experts in recent years have warned that many
Americans may not be getting as much vitamin D as they need. One
ominous sign: a recent resurgence in cases of rickets, a bone disorder
caused by a lack of the vitamin.
In their new paper, which draws together strands from more than seven
decades of vitamin and flu research, Cannell and his colleagues argue
that vitamin D stimulates production of a natural infection-fighting
substance in the body called cathelicidin.
Although cathelicidin has yet to be studied directly on influenza,
recent research has shown that it attacks a variety of fungi, viruses,
and bacteria - including the bug that causes tuberculosis, researchers
reported last March in Science.
There's also indirect evidence of the sun's role in seasonal flu,
Cannell and his colleagues argue.
In the late 1970s, Soviet scientists inoculated nearly 835 young men in
St. Petersburg with a weakened form of the influenza virus during
different seasons of the year.
The men, they discovered, were eight times more likely to develop fever
and other signs of flu infection in winter than in summer. Repeating
the experiment in another city yielded similar results.
And what of the sun-drenched tropics?
Cannell and his colleagues point to a scattering of studies showing
vitamin D deficiencies even in Hong Kong and other equatorial spots.
Another important clue: A 2003 review of tropical influenza infections
found the virus strikes mainly during the rainy season, presumably a
time of reduced sun exposure.
Maybe yes, maybe no Some researchers find the Vitamin D theory
tantalizing. "It's a wonderful story, and I think there's considerable
substance behind it," says immunologist Dr. Michael A. Zasloff, a
professor at Georgetown University.
Others, however, wonder whether this is just another vitamin fad - just
as vitamin C was once promoted by double Nobel laureate Linus Pauling
as a cure for the common cold.
"They have manipulated the literature (some of it very bad literature)
to prove their points," Dr. James Cherry, a pediatric infectious
disease specialist at UCLA's David Geffen School of Medicine, wrote in
an e-mail.
However, "The hypothesis should be easy to prove or disprove with a
controlled, blinded study," he added.
Vitamin D isn't the only substance being kicked around as a seasonal
stimulus candidate.
The CDC's Scott Dowell favors melatonin, a naturally occurring hormone
whose production is tied to the daily light-dark cycle. Preliminary
research suggests that the hormone might help regulate the body's
immune response.
"I don't know where it's going to lead," he concedes.
Cannell, meanwhile, says he takes 5,000 IU of vitamin D during the
winter months, more than twice the maximum daily recommended dose.
He says he rarely gets sick anymore.

 cosi' esageratamente alta come sembrava.
Ripeto: dovresti verificare a quali Paesi, a quali latitudini e a quali 
persone si riferiscono quei dati, ammesso che siano validi.

 solare, oltre che in base a caratteristiche individuali.
Siamo in inverno, che tu sia in italia piuttosto che altrove sul globo
non fa tutta sta differenza ad esclusione di dove e' buio 24/24.

 resta un'ipotesi...
Vedi anche
http://thechronicleherald.ca/Science/540205.html
Catch rays, nix the flu
Lack of Vitamin D may be why disease goes wild in midwinter
 The winter flu season could be the result of our reduced exposure to
 sunlight, according to a review scheduled to be published in print in
 Epidemiology and Infection next month.
[...]
Lo studio integrale dovrebbe essere visibile qui:
http://tinyurl.com/y8u5df

 non fa tutta sta differenza ad esclusione di dove e' buio 24/24.
A parte che anche d'inverno l'Italia non è come il Canada (sia per la
diversa insolazione sia per le temperature che consentono di stare
all'aperto), la vit. D prodotta dall'organismo nei mesi più assolati viene
accumulata e serve come scorta per i mesi invernali.
Inoltre ci sono altre variabili, come la carnagione chiara o scura. Gli
italiani in genere non hanno la pelle scura, anche se nemmeno pallida come
alcuni popoli nordici.
Comunque, se vuoi fare delle belle "scorpacciate" di benefica (*) vit. D,
non hai che da fare più passeggiate all'aria aperta approfittando delle
belle giornate, imho, e non trascurare i cibi più ricchi di vit. D. :-)
* dico "benefica" perché alcuni studi che ho visto ipotizzano un ruolo
protettivo della vit. D per alcune malattie, suggerendo quindi fabbisogni
minimi più alti di quelli finora raccomandati, senza però arrivare a dosi
con rischio di tossicità.