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Danish scientists: Vitamin D crucial to activating immune defenses

8 Mar 2010

Vitamin D plays a key role in fighting infection by “priming” one of the most important weapons in the body’s immune arsenal, shows recent research.

Vitamin D in the sun (Photo: Perfecto Insecto / flickr)

The discovery could help in the development of new vaccines and ways to combat auto-immune diseases and cancer.

It is well known that vitamin D is vital for calcium absorption and bone health, and some studies have suggested it has an anti-cancer effect.

But until the new research scientists had not realised what a crucial role it played in the immune system.

A team of Danish scientists found that vitamin D can transform inert T-cells – one of the body’s infection-fighting white blood cells – into “killer” cells that seek and destroy unwelcome invaders. Without vitamin D, the cells remain dormant and unable to respond to threats.

The mechanism through which the vitamin primes T-cells involves chemical changes that allow the cells to recognise and respond to harmful foreign proteins.

Some of the T-cells that are activated by vitamin D become “killer” cells, one of the most potent weapons in the immune system. They attack and destroy anything carrying traces of target molecules, including cancer cells. Others turn into “helper” cells that enable the immune system to acquire a “memory”. They send messages about the target to other immune cells so they can recognise it at the next encounter.

The Danish scientists carried out laboratory tests with human T-cells which showed how vitamin D was needed to trigger a vital signalling enzyme. Without this signal, T-cells were not activated when exposed to traces of foreign invaders.

Professor Carsten Geisler from the University of Copenhagen, who led the research reported in the journal Nature Immunology, said:

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 the vitamin has also been implicated in diseases such as cancer and multiple sclerosis, but what we didn’t realise is how crucial vitamin D is for actually activating the immune system – which we know now.

Vitamin D deficiency in Denmark

In 2008 a study from Vejle Hospital showed that half of the Danish population did not have enough vitamin D in the body.

Vitamin D deficiency is linked to osteoporosis, and several studies have shown a possible link between vitamin D deficiency and the development of chronic diseases such as certain types of cancer, diabetes and sclerosis.

The Danish National Board of Health recommends the Danes to take a dietary supplement of between 7.5 to 10 micrograms vitamin D per day in the form of a pill.

The other Nordic countries, England, Canada, and the U.S. are trying to solve the problem of vitamin D deficiency by enriching milk with vitamin D therapy. The Danish health authorities prepares to embark on the idea of doing the same in Denmark when it comes to bread and milk.

Sun and fatty fish are important sources of vitamin D. It is the sun’s UVB rays, which through the skin converts cholesterol to a precursor of vitamin D. The precursor is put into the blood stream through the liver and the kidneys, which produce the final, active form of vitamin D.