May 2, 2000 (San Diego, Calif.) -- Feeding mice the human equivalent of a daily ginkgo biloba supplement reduces by a third the amount of brain damage they experience following a stroke, researchers reported today at the 52nd annual meeting of the American Academy of Neurology. While fellow researchers may have once laughed when lead investigator Wayne Clark, MD, talked about using the popular herbal remedy to treat stroke, the positive results from this study may lead to safety trials in humans.
"Our lab has looked at a variety of drugs being tested for stroke, and a 30% reduction [in the size of the stroke, as seen with ginkgo biloba] is as good as any we've seen," says Clark, who is director of the Oregon Stroke Center at Oregon Health Sciences University in Portland.
Any number of agents in ginkgo biloba might be responsible for its protective effects, Clark says. He and his co-investigators have narrowed the actions down to three -- it is an antioxidant, a blood thinner, and an anti-inflammatory. One or all of these actions may be involved, he says, and there may be others that are presently unknown.
The bad news is that too much ginkgo may be worse than none at all. Mice given twice the amount that had proved beneficial had greater damage to their brains than those that received inactive "placebo" tablets. The higher dose of ginkgo may make the blood too thin, causing bleeding in the brain, Clark explains.
"We do not recommend that patients with stroke take [ginkgo] yet," Clark says. "I do not have any patient data to support this, but it's probably relatively safe to take ginkgo if you're on aspirin [which also is a blood thinner], and you want to take something for memory. But if you're on coumadin or warfarin, I've been recommending not to take it."
- In a study of mice, supplements of ginkgo biloba reduced the amount of brain damage following a stroke by 30%.
- Ginkgo acts as an antioxidant, a blood thinner, and an anti-inflammatory, and researchers believe some or all of these properties may explain its effect against stroke.
- Researchers are not yet recommending ginkgo for stroke patients and caution that mice in the study who received too much ginkgo fared worse than those who took inactive tablets.