Ginkgo Biloba: Memory-Boosting Herb

Ginkgo biloba, a living relic of the dinosaur age, is the oldest surviving species of tree on Earth. Poetically, it helps the oldest surviving people. An extract of ginkgo leaves helps prevent and treat many conditions associated with aging: stroke, heart disease, impotence, deafness, blindness, and memory loss. Recent studies show it also helps treat Alzheimer's disease.



Available over-the-counter at health food stores, ginkgo is just now starting to catch on in the United States, and is not well-known among American physicians. But in Europe -- where most of the research has taken place -- doctors often prescribe gingko for the elderly, accounting for sales of more than $500 million a year.



Medical interest in ginkgo stems from the herb's ability to interfere with the action of a substance called platelet activation factor (PAF), which the body produces. Discovered in 1972, PAF is involved in an enormous number of biological processes. By inhibiting PAF, ginkgo has been shown to have enormous medical potential, particularly in conditions associated with aging.



Unless otherwise noted, the information in this section comes from two European collections of ginkgo studies: Ginkgo Biloba Extract: Pharmacological Activities and Clinical Applications (Paris: Elsevier, 1991), and Rokan Ginkgo Biloba: Recent Results in Pharmacology and Clinic (Berlin: Springer-Verlag, 1988).



Ginkgo and memory


Whether or not people develop Alzheimer's disease, with age, blood circulation through the brain declines. When this becomes significant, the condition is known as cerebral insufficiency. It causes memory lapses, problem-solving difficulties, and other cognitive deficits, but does not progress to dementia. Dozens of European studies demonstrate that ginkgo extract helps restore blood flow through the brain and reverse cerebral insufficiency.



In a 1994, researchers at the Humboldt University of Berlin divided 90 people with cerebral insufficiency (average age 63) into two groups. One group took a placebo; the other, a standardized gingko extract (50 mg three times a day). After three months, the placebo-takers showed only minor cognitive improvement, but those taking ginkgo showed significantly improved memory, concentration, and reaction time. The ginkgo extract caused no side effects.



Gingko improves memory not only in older people with cerebral insufficiency, but also in younger people with normal brain function. British researchers at the University of Leeds gave memory tests to eight women (average age 32), and then gave them a variety of medications: a placebo, and ginkgo extract in doses of 120 mg, 240 mg, and 600 mg. The placebo produced no improvement in memory, but the ginkgo did, with increasing doses showing increasing benefits. The women's memory improved "very significantly" after taking the 600 mg dose.



Ginkgo and Alzheimer's disease


In a 1996 study, German researchers recruited 156 people with either Alzheimer's disease or multi-infarct dementia, and gave half of them a placebo, and half a standardized ginkgo extract (120 mg twice a day). After 24 weeks, compared with the placebo group, those taking ginkgo showed significant improvement in cognitive function, as measured by a variety of standardized tests. About 6% of the ginkgo users reported minor side effects: allergic skin reactions, headache, and stomach upset.



In a report released in 1994, Commission E, the German equivalent of the Food and Drug Administration, endorsed ginkgo for early-stage dementias.



Other uses


European physicians also prescribe ginkgo for:

  • Stroke recovery. Ginkgo improves blood flow through the brain.




  • Coronary artery disease. This is the cause of heart attack. It involves the progressive narrowing of the arteries that nourish the heart. Gingko helps prevent arterial narrowing.




  • Narrowing of the arteries in the legs (intermittent claudication). A year-long study of 36 people with intermittent claudication showed ginkgo produced "significantly greater pain relief [than standard treatment]."




  • Erection impairment caused by lack to blood flow to the penis. Two studies have shown "significant improvement" in erection capacity with ginkgo treatment.




  • Deterioration of the retina (macular degeneration), the nerve-rich area in the eye necessary for sight .




  • Hearing loss resulting from decreased blood flow to the nerves involved in hearing (cochlear deafness). A study comparing ginkgo to standard therapy showed "significant recovery in both groups, but distinctly better improvement in the ginkgo group."




  • Chronic ringing in the ears (tinnitus). A 13-month study of 103 people with chronic tinnitus showed ginkgo "conclusively effective." Ginkgo "improved all the patients" taking the herb.




  • Chronic dizziness (vertigo). Seventy people with chronic vertigo were treated for three months with either ginkgo extract or a placebo. At the conclusion of the trial, 18% of the placebo-takers no longer felt dizzy, compared with 47% of those who took ginkgo, a highly significant difference.


Because ginkgo is not well-known among U.S. physicians, few recommend it. However, if you'd like to use it, or give it to a loved one, ginkgo extract is available at most health food stores and supplement shops. The medicinal chemicals in ginkgo leaves are too dilute to have any effect, so standardized extracts concentrate them by processing 50 pounds of leaves into 1 pound of extract -- a 50:1 extract. For dosage, follow package directions. Cognitive improvement may take several months to become noticeable. Ginkgo side effects, if any, are typically minor -- stomach upset, headache, allergic skin reactions. If any develop, reduce the dose, or stop using ginkgo.