Clear Link Found Between Vitamin D Deficiency and Alzheimer's Disease

Older adults who are severely deficient in vitamin D may be more than twice as likely to develop dementia or Alzheimer’s disease than those who don’t have a deficiency, according to the largest study of its kind, published Wednesday in the journal Neurology.

“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,” noted lead researcher David Llewellyn of the University of Exeter Medical School in a news release.

Llewellyn, who could not be reached for comment by Yahoo Health, looked at several years worth of data on 1,658 Americans ages 65 and older who had taken part in the National Heart, Blood and Lung Institute’s Cardiovascular Health Study. He and his team found that adults who were just moderately deficient in vitamin D had a 53 percent increased risk of developing dementia — the general term for any severe decline in mental ability — while the risk jumped to 125 percent for those who had a severe deficiency. Similarly, for Alzheimer’s disease — the most common type of dementia — the moderately deficient adults were 69 percent more likely to develop it, while the severely deficient had a 122 percent increased risk.

“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,” Llewellyn said. “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.”

Currently, more than five million Americans are living with Alzheimer’s disease, which is the sixth leading cause of death in this country, according to the Chicago-based Alzheimer’s Association. One in three seniors dies with Alzheimer’s or another form of dementia. “We think this study is important,” Keith Fargo, director of scientific programs and outreach with the Alzheimer’s Association (a major funder of Llewellyn’s research), told Yahoo Health in response to the findings. “It’s a relatively large study, and it looks like it does show a pretty substantial link.… It just doesn’t show us why there is a link.” One hypothesis, Fargo noted, is that the brain — including the hippocampus, which is one of the first areas to break down with Alzheimer’s — is full of vitamin D receptors.