Ginkgo biloba: brain power in a bottle?
by Jennifer Pitzi Hellwig
Is ginkgo biloba a mental health miracle or just another yet-to-be-proven-effective dietary supplement? The answer lies somewhere in between.
Chances are you've heard of ginkgo biloba–the dietary supplement with the strange-sounding name–even if you don't know exactly what it is or what it does. Advertisements call the herb "the thinking person's supplement," and claim that it improves memory and concentration and enhances mental focus.
An extract made from the leaves of the ginkgo biloba tree, ginkgo has been used medicinally by Chinese herbalists as early as 3000 B.C. The tree itself is so primitive that it doesn't produce flowers, and so hardy that one tree actually survived atomic destruction at Hiroshima. The key to ginkgo's efficacy seems to be a substance that scientists have dubbed EGb 761.
Ginkgo is the most popular botanical extract in Europe, and there are more than 400 scientific studies attesting to its ability to increase blood flow and protect the nervous system. In Germany the extract has been the subject of hundreds of scientific studies. These studies show that among other things, EGb 761 helps keep platelets in the blood from clumping together. That's why ginkgo extract is prescribed in low doses (40 mg a day) in Europe for patients with circulatory problems. Much higher doses (240 mg a day) are used to treat cognitive deficits, such as memory loss.
Ginkgo and Alzheimer's
Public interest in the medicinal powers of ginkgo was fueled in the United States in the fall of 1998 when a study published in the prestigious Journal of the American Medical Association (JAMA) reported that ginkgo had a positive effect on the mental status of people with dementia, including those with Alzheimer's disease.
The researchers studied men and women with mild to moderate dementia that resulted either from stroke or Alzheimer's disease. The subjects were given either daily ginkgo supplements or a placebo. Results indicated that approximately 26% of the patients taking ginkgo showed an improvement in mental status (roughly equivalent to a delay of six months' progression of the disease), compared with 15% taking placebo. And 37% of those taking ginkgo exhibited improved social functioning, compared with 23% in the placebo group. The effect was most pronounced in the subjects who were the least impaired, suggesting that if Alzheimer's is treated early enough, dementia might be postponed.
This study, although seemingly favorable, should be considered with caution. When it was published, critics questioned the methods used to assess improvement, and even the researchers warned that ginkgo will not cure dementia or prevent Alzheimer's disease. The unanimous consensus is that although the results appear promising, it is premature to consider ginkgo a treatment for Alzheimer's disease; more research will be necessary to determine its effects.
Improvement for forgetfulness?
Meanwhile, millions of generally healthy Americans are losing their keys and forgetting phone numbers daily. Will ginkgo work for them, as the advertisements seem to imply? The answer is an unequivocal maybe.
"Ginkgo is not a smart pill," according to Varro E. Tyler, Ph.D., dean emeritus of the Purdue University School of Pharmacy and a leading U.S. expert on herbal remedies. However, in Germany, where ginkgo is a top-selling herb, studies have shown it to be effective in some people for improving short-term memory loss and concentration.
Short-term memory loss and decreased concentration, which we've all experienced to some degree, can have several different causes. One factor is decreased blood flow to the brain. This is where ginkgo may help, because it acts as a blood thinner, thereby improving blood flow and oxygen transport to the brain.
But how do you know if blood flow is your problem? Unless you've received a diagnosis from a physician, you don't. But since studies on ginkgo show it to be safe, it might be worth giving it a try. The recommended dose is 40 mg three times a day, but if after a month you see no improvement in memory with this dosage, you likely won't see any improvement at all.
In August, 2002, a study published in JAMA found that ginkgo did not improve memory or concentration in healthy older adults with no mental function decline. In this study, subjects took 40 mg of ginkgo (Ginkoba brand) or a matching placebo three times daily for six weeks. The results showed no difference in memory or concentration changes between the two groups. These findings suggest that people with normal mental function probably won’t benefit from taking ginkgo.
What to look for when buying ginkgo
Be aware that not all ginkgo products are the same. Many do not contain all the active ingredients. Avoid bargain prices. If it's the real thing, the label should read at least 24% "flavonoids" or "ginkgo flavone glycosides" and 6% "ginkgolides" or "terpene lactones." There are no known side effects beyond stomach upset, but again, Dr. Tyler advises against the use of any herb by pregnant or nursing women. Those taking blood thinners–aspirin, garlic, vitamin E, ginger, or Coumadin (among others)–should use ginkgo only under a doctor's supervision.
Resources:
The Herb Research Foundation
http://www.herbs.org
The United States Food and Drug Administration Center for Food Safety and Applied Nutrition
http://www.cfsan.fda.gov
Sources:
Le Bars PL, Katz MM, Berman N, et al. A placebo-controlled, double-blind, randomized trial of an extract of ginkgo biloba for dementia. JAMA 1997;278:1327-1332.
Morgan P, Tyler VE. Best bets in the herb aisles. Prevention, 1998;50(3).
Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement: A randomized controlled trial. JAMA. 2002;288:835-840.
Last reviewed August 2002 by Medical Review Board
