Scientists find why "sunshine" vitamin D is crucial

LONDON Mon Mar 8, 2010 11:50am EST

1 of 2. A jogger runs along the shore of Manly Beach in Sydney September 1, 2008.

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LONDON (Reuters) - Vitamin D is vital in activating human defences and low levels suffered by around half the world's population may mean their immune systems' killer T cells are poor at fighting infection, scientists said on Sunday.

The findings by Danish researchers could help the fight against infectious diseases and global epidemics, they said, and could be particularly useful in the search for new vaccines.

The researchers found that immune systems' killer cells, known as T cells, rely on vitamin D to become active and remain dormant and unaware of the possibility of threat from an infection or pathogen if vitamin D is lacking in the blood.

"When a T cell is exposed to a foreign pathogen, it extends a signaling device or 'antenna' known as a vitamin D receptor, with which it searches for vitamin D," said Carsten Geisler of Copenhagen University's department of international health, immunology and microbiology, who led the study.

"This means the T cell must have vitamin D or activation of the cell will cease. If the T cells cannot find enough vitamin D in the blood, they won't even begin to mobilize."

Scientists have known for a long time that vitamin D is important for calcium absorption, and that there is a link between levels of the vitamin and diseases such as cancer and multiple sclerosis.

"What we didn't realize is how crucial vitamin D is for actually activating the immune system -- which we know now," Geisler wrote in the study in the journal Nature Immunology.

Most Vitamin D is made by the body as a natural by-product of the skin's exposure to sunlight. It can also be found in fish liver oil, eggs and fatty fish such as salmon, herring and mackerel, or taken as a supplement.

Almost half of the world's population has lower than optimal levels of vitamin D and scientists say the problem is getting worse as people spend more time indoors.

Geisler and his research team said the findings offered much needed information about the immune system and would be of particular use when developing new vaccines.

"This is important not only in fighting disease but also in dealing with anti-immune reactions of the body and the rejection of transplanted organs," they wrote.

Active T cells multiply at an explosive rate and as well as fighting infection, can also mistakenly attack the body itself.

After and an organ transplant, for example, T cells can attack the new organ as a "foreign invader," and in autoimmune disease, hypersensitive T cells mistake parts of the body's own cells as threats, prompting the body to attack itself.

Geisler said there were no definitive studies on the optimal daily vitamin D dose but experts recommend 25 to 50 micrograms.

(Editing by Noah Barkin)

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Comments (9)
pattipdx wrote:
Does this mean my holiday to Spain is medically necessary? My next RX will be 2 weeks in Majorca. Awesome.

Mar 08, 2010 11:47am EST  --  Report as abuse
TipTop wrote:
For years we have heard how important it is for health to have daily doses of sunlight to use vitamin D effectively. With this story, it makes it more crucial. My concern is that vulnerable populations don’t always get sunlight. The US Department of Health should set a standard that should be enforced for vulnerable populations who can not control that access to sunlight such as kids in group homes/academies, prisoners, mental patients, and hospitalized patients and even those on long term bed rest at home.

Mar 08, 2010 12:00pm EST  --  Report as abuse
That’s the ticket. I’ll tell my wife I have to go fishing because my Vitamin D is low. Fishing is medically necessary – else, the cost of my health insurance will go up.

Mar 08, 2010 1:32pm EST  --  Report as abuse
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