Just 15 minutes outside everyday could lengthen everyone's life, say scientists

High doses of Vitamin D - which is mainly absorbed through the skin from UV rays - can help dramatically slash the risk of dying, they said.

The vitamin, which is also found in eggs and oily fish, helps the body take in calcium to build bones, can help cancer victims live longer.

Good for you: Walkers enjoying the sun at Sutton Bank, North Yorkshire, are likely to live longer because they're absorbing vitamin D

But its overall effect on lifespan was unknown until now.

Austrian researcher Harald Dobnig found the risk of death doubles if people only have a quarter of what are considered healthy levels of Vitamin D.

Most doctors believe people should have between 20 to 30 nanograms per millilitre of of the 'sunshine vitamin'.

Yet, alarmingly, only 20 per cent of Britons are estimated to have absorbed enough of the essential nutrient and 15 per cent have dangerously low levels.

This is thought to because of our long, dark winters and due to the fact many people spend large amounts of time indoors.

The findings add extra weight to experts' belief that just 15 minutes outdoors - without sun cream - would do everyone some good.

Dr Dobnig found that the quarter of volunteers with the lowest levels of vitamin D in their blood were more likely to have died.

He said: "This is the first association study that shows vitamin D affects mortality regardless of the (primary) reason for death."

Dr Dobnig and colleagues at the University of Graz, who reported their findings in the Archives of Internal Medicine, studied more than 3,200 people with an average age of 62 who were scheduled for a heart examination between 1997 and 2000.

During an eight-year follow-up programme, the researchers found that the quarter of volunteers with the lowest levels of vitamin D in their blood were more likely to have died.

Dr Dobnig discovered the risk was doubled for people with between 5 to 10 nanograms per millilitre of vitamin D in their blood, even when factors such as heart disease, exercise and other conditions were taken into account.

What causes this effect is not clear, but the internist and endocrinologist pointed to a host of studies suggesting links to high blood pressure, cancer and fractures as places to begin looking.

The potential health risk of low levels of vitamin D should also prod your GP to be more aware of the problem, especially for the immobile, elderly and others who spend a great amount of time indoors, he said.

Many doctors agree that people with low levels of vitamin D cannot make up for it safely by sitting in the sun, but should take supplements.

"These results should prompt us to perform vitamin D measurements on a more frequent basis especially in populations at risk," Dr Dobnig said.

In adults, vitamin D deficiency can lead to osteoporosis, and it can lead to rickets in children.

A number of recent studies have also indicated vitamin D may offer a variety of other health benefits, including protecting against cancer, peripheral artery disease and tuberculosis.

Last week, U.S. researchers said vitamin D may extend the lives of people with colon and rectal cancer.