Research conflicts on whether sun exposure is harmful or beneficial, but a new study suggests that it may ward off dementia later in life. Researchers at the University of Exeter in the U.K. conducted the largest study to date on whether vitamin D levels have any associations with risk for dementia, including Alzheimer’s disease.

Conclusions from the study suggest that for people over 65, vitamin D deficiency is, in fact, linked to increased dementia risk which was more than double in individuals with severe deficiency compared with those with adequate amounts.

The six-year-long investigation followed 1,658 adult Americans aged 65 and older who were at the start free from dementia, stroke, and heart disease. During the study period, subjects with moderate vitamin D deficiency, defined as  between 25 and 50 nanomoles per liter of blood, exhibited a 53 percent increase in risk for dementia compared with subjects having more 50 or more nanomoles per liter. Those with severe deficiency, defined as 25 or fewer nanomoles per liter, showed risks that were 125 percent higher.

“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,” said senior author David Llewellyn. “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.”

Vitamin D is produced in sun-exposed skin. Vitamin D can also be acquired from fatty fish such as tuna and salmon as well as fortified foods. The authors of the current report did not issue official advice on increasing vitamin D consumption.

There is an ongoing controversy regarding the health benefits and potential effects of vitamin D. The latest policy update to come from medical experts suggests that screening for vitamin D deficiency is unwarranted. Whether exposure to sunlight is healthy or not is also a topic of ongoing debate. Recently, the acting U.S. Surgeon General issued a bold statement calling for a paradigm shift away from tanning.