April 13, 2009
Vitamin D, sometimes called the sunshine vitamin because the body makes it upon exposure to sunlight, may help protect the brain against the ravages of dementia, British researchers report. Although more research is needed, the scientists found that older people who had low blood levels of the vitamin were at increased risk for developing memory loss and other symptoms of Alzheimer's disease late in life.
The study, which appeared in the Journal of Geriatric Psychology and Neurology, was based on data from 1,766 seniors. All were 65 or older and part of the Health Survey for England in 2000 study.
The study found that as levels of vitamin D went down, levels of cognitive impairment went up. Compared to those with optimum levels of Vitamin D, those with the lowest levels were more than twice as likely to be cognitively impaired.
About 12 percent of the participants had memory problems, and the lower their vitamin D level, the more likely they were to be in that group. Compared with those in the highest one-quarter for serum vitamin D, those in the lowest were 2.3 times as likely to be impaired, even after statistically adjusting for age, sex, education and ethnicity. Men showed the effect more strongly than women.
"This is the first large-scale study to identify a relationship between Vitamin D and cognitive impairment in later life," said study co-author Dr. Iain Lang from the Peninsula Medical School in the U.K. "Dementia is a growing problem for health services everywhere, and people who have cognitive impairment are at higher risk of going on to develop dementia. That means identifying ways in which we can reduce levels of dementia is a key challenge for health services."
Dr. Lang added: "For those of us who live in countries where there are dark winters without much sunlight, like the U.K., getting enough vitamin D can be a real problem, particularly for older people, who absorb less vitamin D from sunlight."
One way to address this deficit, Dr. Lang suggested, might be to provide older adults with vitamin D supplements, though further research is needed to explore the possible link between the nutrient and its possible role in Alzheimer's disease. "We need to investigate whether vitamin D supplementation is a cost-effective and low-risk way of reducing older people's risks of developing cognitive impairment and dementia."
"The cause of dementia is not vitamin D deficiency," added lead author David Llewellyn, a research associate at Cambridge University. "It's a very complicated disease. But while further research is needed, vitamin D supplementation is cheap, safe and convenient, and may therefore play an important role in prevention."
Vitamin D has long been known for its bone-strengthening properties. That's one reason it is added to milk. But a growing number of studies point to additional benefits, like lowering the risk of diabetes and certain cancers.
In addition to fortified drinks like milk, soy milk and some juices, the vitamin is also found in oily fish like salmon, mackerel, bluefish, catfish, sardines and tuna, as well as cod liver oil and fish oils. Fish oils have also been linked to a lower risk of Alzheimer's disease.
David J. Llewellyn, Ph.D., Kenneth Langa, M.D., Ph.D., and Iain Lang, Ph.D.: "Serum 25-Hydroxyvitamin D Concentration and Cognitive Impairment." Journal of Geriatric Psychiatry and Neurology. February 4, 2009. The Peninsula College of Medicine and Dentistry.