Study shows ginkgo doesn’t help prevent dementia

By Richard Craver
JOURNAL REPORTER
Published: November 19, 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 the results of a $30 million study released Tuesday.

The study, which appears in this week’s issue of the Journal of the American Medical Association, 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 of Wake Forest University Baptist Medical Center, the principal Wake Forest 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 3,069 study participants, all of whom were 75 or older and had either normal cognition or mild cognitive impairment. The study was conducted by Wake Forest, the University of Pittsburgh, Johns Hopkins University and the University of California, Davis.

Previous independent research had held out promise that gingko might help with preventing the development of Alzheimer’s and other forms of dementia because it may increase blood flow, in particular to the brain.

Americans spend more than $110 million on ginkgo each year, according to the Nutrition Business Journal. Ginkgo supplements are also 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 similar long-term approaches.

The study, as expected, received criticism from the alternative-nutrition community.

The American Botanical Council said that the study needed to be conducted longer than six years to provide a better measurement of the effectiveness of ginkgo. It also said that another weakness of the study was the lack of an active control since “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.

The council cited 16 controlled clinical trials that “have demonstrated benefits of various ginkgo extracts for healthy, noncognitively 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 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 of Wake Forest. “Our best strategy is to prevent dementia before it begins.“

The study was conducted primarily to determine whether ginkgo would decrease the incidence of all types of dementia and, more specifically, reduce the incidence of Alzheimer’s. The study also aimed to evaluate ginkgo for its effects on overall cognitive decline, functional disability, incidence of cardiovascular disease and stroke, and total mortality.

About 20 percent of the participants were found to have dementia during their six years of observation - which Williamson said is representative of the typical U.S. population for people 75 and older. Of those participants, 277 were in the ginkgo group and 246 in the placebo group.

“It is very unlikely that ginkgo biloba is effective at any dose over a five-year period and in anyone over 75 years old,“ Williamson said. “It is also ineffective in people with signs of early memory loss.

“What is not known yet is whether the effect of ginkgo biloba might require taking the drug for many, many years - say, 15 years - before there is even a sign of memory loss,“ he said.

It’s too early to determine how much of an effect the study will have on public use and sales of ginkgo products in the dietary-supplement industry, said Richard Nahin, the acting director of the Division of Extramural Research for the National Center for Complementary and Alternative Medicine. The center is another of the five components of the National Institutes of Health that sponsored the study.

The study was overall “well done,“ according to Neil Buckholtz, the chief of the dementias of aging branch for the National Institute on Aging.

“The Holy Grail is to find a source, whether pharmaceutical or alternative, that can stop or delay the onset of Alzheimer’s,“ Buckholtz said. “We will maintain our quest toward that goal.“

Williamson said he was disappointed for his patients, who have been taking ginkgo “for the reasons we conducted the study.“

“Now, my advice is to tell them they are better served not spending their precious retirement resources on ginkgo, but rather on ways to encourage exercise and keep their mind active.“ He added that such advice needs to be thoroughly evaluated by researchers as well.

“I also had people who have parents or grandparents suffering from Alzheimer’s and dementia wanting to know if there was something they could do for themselves to avoid that fate,“ Williamson said.

“The answer is that there is nothing definitive I can recommend for preventing dementia.“

n Richard Craver can be reached at 727-7376 or at.

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