Scientists may now have one more weapon in their continuing war against Alzheimer’s disease an herbal medicine called ginkgo biloba, researchers said Tuesday.
Vitamin E, ibuprofen, estrogen and the anti-Parkinson’s drug selegiline have all been shown recently to slow the progression of this devastating disease, which affects more than 4 million Americans.
Now, scientists from the New York Institute for Medical Research report that an extract of ginkgo biloba commonly available in health food stores may be as effective as any of those.
They found that 27 percent of patients who took the herbal extract for six months or longer showed improvements in mental functioning - including reasoning, memory and ability to learn - compared to only 14 percent of those who took a placebo. The results were “modest,” in the words of study author Dr. Pierre L. LeBars, and the team has no idea which of the many chemicals present in the extract were responsible for the effect.
The team’s results are published today in the Journal of the American Medical Association.
Although the study was paid for by the drug’s manufacturer, it reflects the growing interest among some scientists in so-called alternative medicine, which makes greater use of atural products rather than synthetic drugs. Some researchers question the use of such natural products because their composition varies from lot to lot and the complex mixture of components makes it difficult to determine which constituents are effective.
Zaven Khachaturian, research director for the Alzheimer’s Association, cautioned that Alzheimer’s patients should not rush to medicate themselves with the drug.
“What’s exciting is, it seems to be fairly safe and gives us a new vista to explore” for drugs that will be even more active, he said. “(But) the results are no better than those with some of the other compounds.”
Khachaturian and others also noted that ginkgo extract acts as a blood thinner and could be unsafe for patients who are already taking anti-coagulants or other blood-thinning agents. Other potential side effects include nausea, diarrhea and flatulence.
Ginkgo is extracted from the bark, nuts and leaves of the ginkgo biloba or maidenhair tree, which grows mainly in temperate climates. It is a complex mixture of as many as 300 chemicals that has been used medicinally for more than 5,000 years because of its antioxidant and anti-inflammatory properties and a perceived ability to increase blood flow.
Commercial ginkgo preparations can have vastly different compositions, depending upon the technique used to extract active ingredients from leaves and fruit.
The particular form studied in the new report is called EGb 761. It is widely used in Europe for the treatment of cognitive disorders and has been approved by the German equivalent of the U.S. Food and Drug Administration for the treatment of dementia, the impairment of thought processes characteristic of Alzheimer’s. EGb 761 is not generally available in the United States, although many other formulations are.
LeBars and his colleagues initially recruited 309 patients for their study - most with Alzheimer’s, but about 50 with dementia caused by strokes. More than a third dropped out, however, an unusually high number for such a clinical trial. Half the remaining patients received 120 milligrams of EGb 761 per day, while the other half received a placebo.
The mental abilities of the patients were assessed on two different objective scales at the beginning of the test and at regular intervals.
“Compared with the placebo group, the EGb group included twice as many patients whose cognitive performance improved and (only) half as many whose social functioning worsened,” LeBars told a news conference in Washington Tuesday. “What is the mode of action? We really don’t know … The study is the source of more questions than answers.”