Oct. 14, 2008 - Clinical trial findings crush hopes that high-dose B vitamins -- folate and vitamins B6 and B12 -- might slow mental decline in people with Alzheimer's disease.
The findings come from a study of people who already had mild-to-moderate Alzheimer's.
"This regimen of high-dose vitamin B supplements does not slow cognitive decline in individuals with mild to moderate Alzheimer's disease," conclude University of California, San Diego researcher Paul S. Aisen, MD, and colleagues.
Though the study looked only at people who already suffered Alzheimer's disease, Aisen says people should not take high doses of B vitamins to avoid mental decline -- at least until clinical trials show it works.
"I do not recommend high-dose vitamins for anybody unless they have a deficiency or an established indication for such treatment," Aisen tells WebMD. "Risk of Alzheimer's disease is not an indication for high-dose B vitamins."
Andrew Shao, PhD, sees it differently. He's vice president for scientific and regulatory affairs at the supplement industry trade group Council for Responsible Nutrition.
"Vitamins do not have the powerful effects of pharmaceuticals. They are subtle and take a long time to show an effect," Shao tells WebMD. "An earlier study of healthy older people who took B vitamins over three years did show a slowing of cognitive decline."
Fortunately, clinical trials are testing whether B vitamins can slow age-related loss of mental function, says Robert J. Clarke, MD, of Oxford University, England.
"Several large-scale trials are currently addressing this question and the results of several such trials are expected in the next few months," Clarke tells WebMD in an email interview. "It would be prudent to await the results of these ongoing trials ... before making recommendations on the use of B vitamins to avoid or ameliorate cognitive decline in cognitively intact individuals."
There are risks to taking any drug or supplement. One disturbing finding from the Aisen study was that Alzheimer's patients taking high-dose B vitamins suffered more depressive symptoms than those who took placebo pills.
"It was an unexpected finding and could be due to chance, but it is a possible risk, and it might mean in people who are not demented there also are risks to high-dose B vitamins," he says. "Without evidence of efficacy, I do not recommend this treatment to people who are worried about Alzheimer's disease."
B Vitamins, Homocysteine, and Alzheimer's
Folate (a form of vitamin B9), vitamin B6, and vitamin B12 reduce levels of homocysteine in the body. People with Alzheimer's disease tend to have high homocysteine levels. Moreover, evidence suggests that homocysteine makes the main ingredient in brain-clogging plaque -- amyloid -- more toxic.
There's no doubt that B vitamins lower homocysteine. In the Aisen study, Alzheimer's patients who took folate (5 milligrams/day), vitamin B6 (25 milligrams/day), and vitamin B12 (1 milligrams/day) had 31% lower homocysteine levels than patients taking placebo.
But that didn't seem to help -- at least among patients with no underlying vitamin deficiency.
"We were successful in lowering homocysteine, but it had absolutely no effect on the clinical symptoms of Alzheimer's disease," Aisen says.
Shao notes that patients in the Aisen study did not have particularly high homocysteine levels to begin with. He says the study has not answered the question of whether Alzheimer's patients with extremely high homocysteine levels might benefit from high-dose B vitamins.
It's time to move on, says Aisen, who serves as director of the Alzheimer's Disease Cooperative Study (ADCS) that investigates potential new Alzheimer's treatments.
"I think this study is the end of the treatment of Alzheimer's disease with these vitamins," he says.
The Aisen study, and an editorial by Clarke and colleague Derrick A. Bennett, PhD, appear in the Oct. 15 issue of TheJournal of the American Medical Association.