Ginkgo fails to prevent Alzheimer's

CHICAGO - The dietary supplement ginkgo, long promoted as an aid to memory, didn't help prevent dementia and Alzheimer's disease in the longest and largest test of the extract in older Americans.

"We don't think it has a future as a powerful antidementia drug," said Dr. Steven DeKosky of the University of Virginia School of Medicine, who led the federally funded study.

Extracts from ginkgo tree leaves have antioxidant and anti-inflammatory effects, but earlier research on ginkgo and memory showed mixed results. Annual US sales of the supplement reached $107 million in 2007, according to Nutrition Business Journal estimates.

Ginkgo has been believed to protect the brain by preventing the buildup of an Alzheimer's-related protein or by preventing cell-damaging oxidative stress. It's been used for leg pain, ringing in the ears, and sexual dysfunction.

For the new study, appearing in today'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 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.

Participants were screened for dementia every six months. 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. When the researchers looked only at Alzheimer's disease, that rate, too, was similar.

At the start, some people showed mild difficulties with thinking; ginkgo didn't work to prevent dementia in those people either.

ASSOCIATED PRESS