Sunlight -- or, more to the point, the vitamin D contained in solar rays -- may be the secret to staving off dementia and Alzheimer's disease, says a new study from the United Kingdom.

Researchers from the University of Exeter, located in South West England, have determined getting adequate amounts of vitamin D can significantly lower the risk of cognitive disorders in older individuals, according to a UE news release.

In the most comprehensive research of its kind, an international team, led by David Llewellyn from the university's medical school, found study participants who were severely deficient of vitamin D were more than twice as likely to develop dementia and Alzheimer's disease.

Partially funded by the Alzheimer's Association and published in Aug. 6 online issue of Neurology, the medical journal of the American Academy of Neurology, the study looked at 1,658 adult Americans aged 65 and over, who had previously participated in the Cardiovascular Health Study and were able to walk unaided and were free from dementia, cardiovascular disease and stroke at the start of the research period.

Study participants were tracked for six years to observe which of them ended up developing Alzheimer's and other forms of dementia.

The science team discovered participants who were moderately deficient in vitamin D had a 53 percent higher risk of developing dementia of any kind -- and the risk increased to 125 percent in those who were severely deficient.

The researchers found similar results for Alzheimer's disease, with the moderately deficient group 69 percent and the severely deficient subjects 122 percent more likely to develop the debilitating disorder, for which there's not yet a cure.

"We expected to find an association between low Vitamin D levels and the risk of dementia and Alzheimer's disease, but the results were surprising -- we actually found that the association was twice as strong as we anticipated," Llewellyn said in the UE release, adding that "clinical trials are now needed to establish whether eating foods such as oily fish or taking vitamin D supplements can delay or even prevent the onset of Alzheimer's disease and dementia."

But, "we need to be cautious at this early stage and our latest results do not demonstrate that low vitamin D levels cause dementia. That said, our findings are very encouraging, and even if a small number of people could benefit, this would have enormous public health implications given the devastating and costly nature of dementia," he said.

Conditions leading to dementia are suffered by an estimated 44 million people worldwide -- a number UE researchers expect to triple by 2050, as the worldwide population rapidly ages.

Meanwhile, at least one billion people are thought to have low vitamin D levels.

Previous research concluded people with low vitamin D levels are more likely in the future to experience cognitive problems, but the latest study confirms that link translates into a notable increase in the risk of Alzheimer's disease and dementia.

Vitamin D comes from three main sources, exposure of skin to sunlight, foods such as oily fish, and supplements -- although the researchers note it's too early to say the vitamin D from sunlight or supplements witl definitely fight dementia or Alzheimer's.