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Study casts doubt on use of ginkgo biloba

Journal photo by David Rolfe

Ginkgo trees outside of Wake Forest University Baptist Medical Center.

By Richard Craver | Journal Reporter

Published: November 18, 2008

Ginkgo biloba, a top-selling herb marketed for memory enhancement, has no effect at preventing the onset of dementia or Alzheimer's disease, according to a $30 million study released today.

Researchers at Wake Forest University Baptist Medical Center helped conduct the study over an eight-year period. About 700 Triad residents were among the 3,069 study participants, all age 75 or older who had either normal cognition or mild cognitive impairment.

The study appears in this week's issue of the Journal of the American Medical Association. Besides Baptist, the study was conducted at the University of Pittsburgh, Johns Hopkins University and the University of California-Davis.

The study tested the effectiveness of 120 milligrams of ginkgo twice daily vs. a placebo in lowering the incidence of dementia and Alzheimer's. The gingko product used in the study was supplied by Schwabe Pharmaceuticals and is sold as Ginkgold Max under the Nature's Way label.

"We were very disappointed in the results of the study because we were very hopeful that gingko would prove beneficial," said Dr. Jeff Williamson, the principal Baptist investigator for the study.

"In addition to its widespread use based on the belief that it helps memory function, ginkgo biloba had enough promising circumstantial evidence from laboratory and animal studies, and enough safety information, to warrant a full-scale test in humans."

The study has worldwide implications considering earlier research had held out promise that gingko might help with preventing the development of Alzheimer's and other forms of dementia because it can increase blood flow to the brain.

More than $110 million is spent annually by Americans on ginkgo, according to the Nutrition Business Journal. Ginkgo supplements also are among the best selling herbal medications in Europe.

The researchers said that the study was the largest clinical trial to evaluate the effects of ginkgo on dementia. Other studies, including one in France, are taking a similar long-term approach with ginkgo.
The study, as expected, received criticism from the alternative-nutritional community.

The American Botanical Council said that the study needed to be conducted longer than six years so to provide a better measurement for the effectiveness of ginkgo. It also said that the study was weakened because "no conventional pharmaceutical drug has ever demonstrated the ability to prevent the onset of dementia or diminish its progression."

"Ginkgo's benefits must be viewed in the context of the entirety of the published clinical data," said Mark Blumenthal, the founder and executive director of the council.

He said that other controlled clinical data "support the use of ginkgo extract for treating symptoms of mild cognitive impairment and even early stage Alzheimer's disease." The council also cited 16 controlled clinical trials that "have demonstrated benefits of various ginkgo extracts for healthy, non-cognitively impaired adults."

Alzheimer's is one of the most common forms of dementia in older people, affecting nearly 4.5 million Americans, according to the National Institute on Aging, one of the five national sponsors of the study. It is an incurable disease with a slow progression beginning with mild memory loss and ending with severe brain damage and death.

"Alzheimer's disease is a devastating disease affecting large numbers of older adults," said Dr. Gregory Burke, the lead investigator for the Baptist clinical site. "Our best strategy is to prevent dementia before it begins."