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Source: ONE News/Close Up
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
signalling 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 mobilise."
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 realise 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.
