London Telegraph 
March 8, 2010
Vitamin D is crucial to the fending off of infections, claims new research.
The so-called sunshine vitamin, which can be obtained from food or manufactured by human skin exposed to the sun, plays a key role in boosting the immune system, researchers believe.
In particular it triggers and arms the body’s T cells, the cells in the body that seek out and destroy any invading bacteria and viruses.
Scientists at the University of Copenhagen have discovered that Vitamin D is crucial to activating our immune defences and that without sufficient intake of the vitamin, the killer cells of the immune system – T cells – will not be able to react to and fight off serious infections in the body.