Insufficient levels of vitamin D may reduce our immune system’s ability to react to infection, says new research from Denmark.

Vitamin D is necessary to trigger T cells – the immune system’s killer cells – into action, and insufficient levels of the vitamin mean the cells remain dormant and inactive, according to findings published in Nature Immunology.

“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 realize is how crucial vitamin D is for actually activating the immune system – which we know now,” said scientists from the University of Copenhagen.

The study adds to an ever growing body of science supporting the benefits of maintaining healthy vitamin D levels.

In adults, it is said vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 diabetes.

“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,” explained Prof Geisler. “This means that 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.”

Vitamin D forms in our skin in response to sunlight. However, care should be taken to avoid burning or over-exposure. Vitamin D is also found in foods such as oily fish, eggs, fortified margarines, some breakfast cereals and vitamin supplements.

The current Recommended Dietary Intake (RDI) for adults is 400IU daily, however many health experts and researchers conclude that this level may be insufficient.

Source: Nutraingredients.com, 8 March 2010 and nhs.uk