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Brain & Nervous System Health Center

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Vitamins D and E May Affect Dementia Risk

Studies Show Blood Levels of Vitamins D and E Are Linked to Risk of Cognitive Decline

Can Vitamin D Prevent Dementia? continued...

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.

"At present, there is not rigorous evidence for health benefits of vitamin D supplementation in community-dwelling individuals, beyond avoiding the very low levels," he says. The bottom line? "Routine supplementation of vitamin D is not, at present, justified."

Michael Holick, MD, PhD, is not as cautious in his interpretation of the new findings or in his vitamin D recommendations. As a professor of medicine, physiology, and biophysics at the Boston University School of Medicine and the director of the Vitamin D, Skin, and Bone Research Laboratory there, Holick has been warning Americans about the dangers of vitamin D deficiency for most of his career.

"I am not at all surprised that vitamin D deficiency is associated with cognitive decline," he tells WebMD. His advice is simple: "Take more vitamin D. All adults should consume 2,000 international units (IU) of vitamin D per day."

Currently, the dietary reference intake (DRI) for vitamin D is 200 IU per day for adults aged 14 to 50, 400 IU per day for adults 50 to 71, and 600 IU per day for those older than 71. The Institute of Medicine is considering new recommendations for vitamin D intake.

But the jury is in, according to Holick, and the time to supplement is before you develop signs of dementia or other diseases. "The role of vitamin D is to prevent and reduce risk of disease more so than treat them," he says.

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