November 19, 2008
Alzheimer’s Not Helped By Ginkgo Supplement
Researchers found a dietary supplement that promises to help memory, didn't help prevent dementia and Alzheimer's disease in the largest study ever of the extract.
"We don't think it has a future as a powerful anti-dementia drug," said Dr. Steven DeKosky of the University of Virginia School of Medicine, who led the federally funded study.
U.S. sales of the supplement reached $107 million in 2007, according to Nutrition Business Journal estimates.
Ginkgo was believed to protect the brain by preventing the buildup of an Alzheimer's-related protein; it's also been used for leg pain, ringing in the ears and sexual dysfunction.
The new study was published in Wednesday's Journal of the American Medical Association.
Researchers recruited more than 3,000 people, ages 75 and older, from voter and mailing lists in Maryland, Pennsylvania, California and North Carolina.
Half of participants were randomly assigned to take 120 milligrams of ginkgo biloba twice a day, a typical dose taken by people who think it may help memory.
The others took identical dummy pills.
Every six months participants were screened for dementia.
After six years, dementia had been diagnosed at a similar rate in both groups; 277 in the ginkgo group and 246 in the group taking the dummy tablets. The rate was also similar when researchers looked at Alzheimer's disease.
DeKosky said there was no difference in the rate of adverse events such as heart attacks and gastrointestinal bleeding between the groups.
However, the study didn't test whether ginkgo improves thinking and memory in the short term.
"It would have been terrific if this worked. It's inexpensive, available and relatively safe," said Paul Solomon, professor of neuroscience at Williams College in Williamstown, Mass.
"Now with this kind of evidence, you can confidently tell people it didn't show benefit in more than 3,000 people in six years of research," Solomon said.
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