Ginkgo biloba, a readily available natural product, has been the focus of recent media reports as a potential treatment for Alzheimer's disease. Although a 1997 study in the United States suggests that a ginkgo extract may be of some help in treating the symptoms of Alzheimer's disease and vascular dementia, there is no evidence that ginkgo biloba will cure or prevent Alzheimer's disease.
In addition, some recent case studies imply that daily use of ginkgo biloba extracts may cause side effects, such as excessive bleeding, especially when combined with daily use of aspirin. Much more research is needed before scientists will know whether and how ginkgo biloba extracts benefit people.
Uses Outside the United States
For centuries, extracts from the leaves of the ginkgo biloba tree have been used as Chinese herbal medicine to treat a variety of medical conditions. In Europe and some Asian countries, standardized extracts from ginkgo leaves are taken to treat a wide range of symptoms, including dizziness, memory impairment, inflammation, and reduced blood flow to the brain and other areas of impaired circulation. Because ginkgo biloba is an anti-oxidant, some claims have been made that it can be used to prevent damage caused by free radicals (harmful oxygen molecules). Although Germany recently approved ginkgo extracts (240 mg a day) to treat Alzheimer's disease, there is not enough information to recommend its broad use.
Research in the United States
Researchers at the New York Institute for Medical Research in Tarrytown, New York, conducted the first clinical study of ginkgo biloba and dementia in the United States. Their findings were published in the Journal of the American Medical Association (October 22/29, 1997). These scientists examined how taking 120 mg a day of a ginkgo biloba extract affected the rate of cognitive decline in people with mild to moderately severe dementia due to Alzheimer's disease and vascular dementia. At the end of the study, they reported a small treatment difference in people given the ginkgo biloba extract.
Three tests were used to measure changes in the condition of participants. First, participants showed a slight improvement on a test that measured their cognitive function (mental processes of knowing, thinking, and learning). Second, participants showed a slight improvement on a test that measured social behavior and mood changes that were observed by their caregivers. Third, participants showed no improvement on a doctor's assessment of change test.
Because 60 percent of the people did not complete the study, findings are difficult to interpret and may even be distorted. In addition, this study did not address the effect of ginkgo biloba on delaying or preventing the onset of Alzheimer's disease or vascular dementia. The researchers recommend more investigation to determine if these findings are valid, understand how ginkgo biloba works on brain cells, and identify an effective dosage and potential side effects.
The National Institute on Aging (NIA) and the Office of Alternative Medicine, both at the National Institutes of Health, are funding a small study to test the effectiveness of ginkgo biloba in treating Alzheimer's disease. This 2-year study at the Oregon Health Sciences University in Portland started in 1997. It will include 42 patients with mild to moderate Alzheimer's disease.
Consulting With Your Doctor
People should consult with their family doctors before using ginkgo biloba extracts. This is especially true for those with disorders in blood circulation or blood-clotting and those taking anti-coagulants such as aspirin. Many different preparations of ginkgo biloba extract are available over the counter. They vary in content and active ingredients. Because not enough research has been done, no specific daily amount of a ginkgo biloba extract can be recommended as safe or effective at this time.
Anyone who is worried about a memory problem should see a doctor. Symptoms similar to those caused by Alzheimer's disease may be caused by other medical conditions, including a high fever, dehydration, vitamin deficiency and poor nutrition, bad reactions to medicines, thyroid problems, depression, or a minor head injury. Medical problems like these are serious and should be treated by a doctor as soon as possible.
For More Information
For more information about Alzheimer's disease and related disorders, contact NIA's Alzheimer's Disease Education and Referral (ADEAR) Center at:
PO Box 8250
Silver Spring, MD 20907-8250
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
National Institutes of Health
National Institute on Aging
Published in May 1998
This document sourced from the Alzheimer's Disease Education and Referral Center, a service of the National Institute on Aging.