Low vitamin D level could double Alzheimer's risk, studies say

Older adults with inadequate levels of vitamin D in their blood may have twice the risk of developing Alzheimer's Disease as seniors with sufficient levels of the vitamin, a new study finds. This new information supports other previous studies.

The research -- based on more than 1,600 adults over age 65 -- found the risk for Alzheimer's and other forms of dementia increased with the severity of vitamin D deficiency.

However, the findings aren't enough to recommend seniors take vitamin D supplements to prevent mental decline. "Clinical trials are now urgently needed in this area," said study researcher David Llewellyn, a senior research fellow in clinical epidemiology at the University of Exeter Medical School in England.

Published online in the August 6 journal Neurology, this is believed to be the largest study yet to find an association between dementia and low levels of vitamin D.

Vitamin D is known for maintaining bone health. It is also thought to moderate cell growth and help control immune function and inflammation. Vitamin D can be obtained through food (salmon, tuna, milk, eggs, cheese, etc.), through the skin after exposure to sunlight and from supplements.

Dementia describes a decline in memory and thinking that interferes with daily life. Alzheimer's is the most common form of dementia, affecting about 5 million Americans, according to the Alzheimer's Association.

For this study, researchers looked at mentally healthy men and women who participated in the U.S. Cardiovascular Health Study between 1992-93 and 1999. At the start, heir blood samples were collected and their mental status was assessed approximately six years later.

During the follow-up, those with low levels of vitamin D were about 1.7 times more likely to develop dementia than those with normal levels. Those with severely low levels were about 2.2 times more likely than those with normal levels to develop dementia, the study found.

The results echo some findings from other, smaller studies, Fargo said. "What's important about this study is the large number of participants," he said. However, experts disagree about the best blood level of vitamin D.

It is not known exactly how low vitamin D may be linked with dementia. There is speculation that the vitamin may clear plaques in the brain linked with dementia. This has been shown in the lab, Fargo said. Vitamin D deficiency has been linked with brain atrophy as well, according to background information contained in the study.

Given the prevalence of Alzheimer's Disease, it is important that people try to maintain a brain healthy diet, which is essentially the same as a heart-healthy diet. That includes foods low in fat and cholesterol. Of course, getting regular physical activity and keeping blood pressure under control are other good measures.

Alzheimer's studies such as this, and more information, can be found on the Alzheimer's Association website www.alz.org. An additional report on vitamin D deficiency and it's relationship to dementia can also be found on this link to a CBS News segment.

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