Ginkgo (Ginkgo biloba ) is the only remaining member of a family of trees that flourished centuries ago in ancient China. Dubbed a living fossil, ginkgo today thrives worldwide in parks and gardens, and in plantations where leaves of carefully pruned ginkgo shrubs are harvested and processed into supplements. Although the people of China have been using the fruits and seeds since 2800 BC, only during the last 20 years has Western medicine begun to recognize the value of ginkgo leaves in the form of a concentrated extract. Today ginkgo leaf extract is one of the most widely prescribed medications in Europe.
What is it good for?
Although often advertised as a "smart pill," human studies of the effectiveness of gingko biloba have had mixed results. Small studies have found that it provided limited benefit for people with various dementias, including Alzheimer's dementia. For instance, a year-long study of 202 Alzheimer's patients at clinics in New York and Boston found that those who took ginkgo improved or halted the deterioration of their mental abilities and social functioning. However, a major 6-year study of over 3,000 elderly people published in the Journal of the American Medical Association found that it had no effect on patients with dementia or Alzheimer's.
Human research has shown that gingko extract increases pain-free walking distance in people with leg pain due to clogged arteries, but more studies are needed. Other human studies indicate that it may help some forms of dizziness, prevent altitude sickness and improve distance vision in people with macular degeneration (breakdown of an area in the back of the eye). In addition, gingko extract appears to have reversed some sexual dysfunction in some people who took the antidepressant drugs Paxil (Paraoxetine), Prozac (Fluoxetine), or Zoloft (Sertraline).
How does it work?
The preparation commonly known as ginkgo biloba extract (GBE) contains several kinds of compounds including flavone glycosides and ginkgolides. These substances may improve circulation throughout the body and brain by inhibiting a blood compound that encourages clotting. They might also strengthen and possibly rebuild capillaries, which may prevent or stabilize structural damage around the brain.
How safe is it?
Twenty years of studies in Europe of ginkgo biloba extract have yielded few reports of serious adverse effects. In a six-month study of more than 8,000 people, fewer than one percent suffered any side effects. Those who did had mild complaints such as stomachaches, headaches, nausea, dizziness or rashes. Large doses can cause irritability, vomiting, and diarrhea. If you or a loved one are showing signs of dementia or circulatory problems, consult a doctor for a diagnosis and appropriate treatment options.
People with bleeding disorders or seizure disorders (epilepsy) should avoid ginkgo extract. Since ginkgo extract thins the blood, don't take it if you are already on anticoagulants such as Coumadin (Warfarin) or aspirin. Ginkgo might also interfere with many other prescription medicines, sometimes with severe consequences, so check with your doctor or pharmacist before taking it.
Avoid touching ginkgo fruit. The pulp can cause severe skin reactions. It can also cause allergic reactions in people allergic to poison oak or poison ivy. Do not eat fresh ginkgo seeds, they are toxic. However, the roasted seeds, eaten in moderation, are safe and considered a delicacy in some cultures.
What's the best way to take it?
Ginkgo must be taken in a highly concentrated form to be effective; a tea made of ginkgo leaves doesn't have enough of the active ingredients to do you any good. You can get the concentrated leaf extract in tablet and liquid form, but keep in mind that the government doesn't regulate herbs as strictly as it does other drugs, so it's sometimes hard to know what you're getting. Quality and potency can vary from product to product. Most preparations claim to contain 24 percent flavone glycosides; typical dosages range from 120 to 240 mg daily. If you decide to take ginkgo, keep in mind that it can take up to 12 weeks to get results.
References
Jellin JM, Gregory P, Batz F, Hitchens K, et al. Pharmacist's Letter/Prescriber's Letter Natural Medicines Comprehensive Database. Stockton, CA: Therapeutic Research Faculty.
Gingko, Alternative Treatments, Alzheimers Association.
LeBars PL, et al. A placebo-controlled, double-blind, randomized trial of an extract of ginkgo biloba for dementia. JAMA;278:1327-1332.
Solomon PR, et al. Ginkgo for memory enhancement: a randomized controlled trial. JAMA 1;288(7):835-40.
Mayo Clinic. Ginkgo (Ginkgo biloba L.).
DeKosky, ST, et al. Ginkgo biloba for prevention of dementia: A randomized controlled trial. Journal of the American Medical Association,; 300(19): 2253-2262.
National Center for Complementary and Alternative Medicine (NCCAM). Ginkgo.
