July 12, 2010 -- Two new studies help clarify the role that certain vitamins may play in the onset of cognitive decline, including risk of Alzheimer's disease.
One study suggests that low blood levels of vitamin D may increase risk for cognitive decline, while another study shows that consuming a diet rich in the antioxidant powerhouse vitamin E may help reduce the risk for dementia, including Alzheimer's disease.
But experts, including the study researchers, caution that it is still too early to make any blanket recommendations about what individuals should eat and what supplements they should take to reduce their risks for age-related cognitive decline and dementia.
In the vitamin D study of 858 adults aged 65 and older, those with the lowest blood levels of vitamin D -- less than 25 nanomoles per liter of blood -- were 60% more likely to show signs of general cognitive decline during the six-year study and 31% more likely to show declines in their ability to plan, organize, and prioritize (so-called executive function), than their counterparts who had sufficient blood levels of vitamin D.
The findings appear in the July 12 issue of the Archives of Internal Medicine.
Vitamin D is often called the sunshine vitamin because our bodies produce it in response to sunlight. Vitamin D has become the "it" vitamin in recent years, as growing research links its deficiency to a host of health problems including heart disease, certain cancers, osteoporosis, diabetes, schizophrenia, and some autoimmune disorders.
Anywhere from 40% to 100% of older adults in the U.S. and Europe may be vitamin D-deficient, according to information cited in the new study.
"Our study demonstrates that low levels of vitamin D are associated with an increased risk of new cognitive problems," study researcher David J. Llewellyn, PhD, of the University of Exeter, England, says in an email. "This raises the possibility that vitamin D supplements may have therapeutic potential for the prevention of dementia and clinical trials are now urgently needed."
"We do not yet know the optimal intake of vitamin D to protect the brain as we need the results of clinical trials to confirm this," he says.
Andrew Grey, MD, of the University of Auckland in New Zealand, co-authored an editorial accompanying the new study that calls for rigorously designed trials. The new study "should serve as a springboard to conduct a randomized placebo-controlled trial to investigate whether vitamin D supplements prevent dementia," he says in an email.
"Similarly, other observational studies have reported associations between lower levels of vitamin D and many other diseases [and] randomized controlled trials of vitamin D supplementation are required to determine whether these associations are causal," he says.
As of right now, "vitamin D should only be measured if clinically indicated -- [such as in] the frail elderly, dark-skinned people -- and those who avoid the sun for religious, cultural, or medical reasons are at risk of clinically important vitamin D deficiency," he says.