Editor’s note: The study does not prove that gingko
biloba is useless in preventing Alzheimer’s disease in people younger than 75.
The study subjects were older 75 and the
chances are good that these people may have already experienced damage in their
brains. In any case, using a drug or herbal supplement may not be the best
approach to preventing Alzheimer’s.
The
solution is in the diet.
For example, we
know eating fish and omega-3 fatty acids help people maintain cognitive
function.
Wednesday Nov 19, 2008 (foodconsumer.org) -- A new study
published in the Journal of the American Medical Association suggests that the
widely used herbal supplement Ginkgo biloba may not help elderly people who are
healthy or have only mild cognitive impairment, to prevent Alzheimer's disease
if they start taking this supplement too late.
The study led Dr. Steven DeKosky, dean of the University
of Virginia School of Medicine involved 3,069 apparently healthy people age 75
or older at five U.S. locations. Participants were free of Alzheimer’s or had
only mild cognitive impairment.
For the study, the researchers assigned 120 mg of extract
from the leaves of the ginkgo tree or a placebo twice a day for about six years
and found the herbal supplement did not make any difference in the rate of
Alzheimer's disease. (Editor’s note: 120 mg is fairly low and early studies
showed high doses make a difference)
Among those who took ginkgo, 18 were diagnosed with
Alzheimer's or other dementia and among those who took the placebo, 16 were
diagnosed with the disease, the study found.
Alzheimer’s disease is incurable. Dr. Murali Doraiswamy
of Duke University Medical Center in Durham, North Carolina was cited by Reuters
as noting that many interventions including statins, estrogen,
anti-inflammatory drugs, vitamin E and drugs called cholinesterase inhibitors
do not deliver any protective effect.
The herbal industry disagreed with the findings. Michael
McGuffin of the American Herbal Products Association was cited as saying that
early studies proved ginkgo relieves symptoms in people with Alzheimer's.
Daniel Fabricant of the Natural Products Association was
cited as saying that studying people younger than about 80 years old may be the
best way to examine the efficacy of ginkgo on Alzheimer’s prevention.
Ginkgo
Introduction
This fact sheet provides basic information about the herb ginkgo—common names, uses, potential side effects, and resources for more information. The ginkgo tree is one of the oldest types of trees in the world. Ginkgo seeds have been used in traditional Chinese medicine for thousands of years, and cooked seeds are occasionally eaten.
Common Names—ginkgo, Ginkgo biloba, fossil tree, maidenhair tree, Japanese silver apricot, baiguo, bai guo ye, kew tree, yinhsing (yin-hsing)
Latin Name—Ginkgo biloba
What It Is Used For
* Ginkgo leaf extract has been used to treat a variety of ailments and conditions, including asthma, bronchitis, fatigue, and tinnitus (ringing or roaring sounds in the ears). * Today, people use ginkgo leaf extracts hoping to improve memory; to treat or help prevent Alzheimer's disease and other types of dementia; to decrease intermittent claudication (leg pain caused by narrowing arteries); and to treat sexual dysfunction, multiple sclerosis, tinnitus, and other health conditions.
How It Is Used
Extracts are usually taken from the ginkgo leaf and are used to make tablets, capsules, or teas. Occasionally, ginkgo extracts are used in skin products.
What the Science Says
* Numerous studies of ginkgo have been done for a variety of conditions. Some promising results have been seen for intermittent claudication, but larger, well-designed research studies are needed. * An NCCAM-funded study of the well-characterized ginkgo product, EGb-761, found it ineffective in lowering the overall incidence of dementia and Alzheimer's disease in the elderly. In this clinical trial, known as the Ginkgo Evaluation of Memory study, researchers recruited more than 3,000 volunteers age 75 and over who took 240 mg of ginkgo daily. Participants were followed for an average of approximately 6 years. * Some smaller studies for memory enhancement have had promising results, but a trial sponsored by the National Institute on Aging of more than 200 healthy adults over age 60 found that ginkgo taken for 6 weeks did not improve memory. * Other NCCAM-funded research includes studies on ginkgo for asthma, symptoms of multiple sclerosis, vascular function (intermittent claudication), cognitive decline, sexual dysfunction due to antidepressants, and insulin resistance. NCCAM is also looking at potential interactions between ginkgo and prescription drugs.
Side Effects and Cautions
* Side effects of ginkgo may include headache, nausea, gastrointestinal upset, diarrhea, dizziness, or allergic skin reactions. More severe allergic reactions have occasionally been reported. * There are some data to suggest that ginkgo can increase bleeding risk, so people who take anticoagulant drugs, have bleeding disorders, or have scheduled surgery or dental procedures should use caution and talk to a health care provider if using ginkgo. * Uncooked ginkgo seeds contain a chemical known as ginkgotoxin, which can cause seizures. Consuming large quantities of seeds over time can cause death. Ginkgo leaf and ginkgo leaf extracts appear to contain little ginkgotoxin. * Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.
Sources
* DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. Journal of the American Medical Association. 2008;300(19):2253–2262. * De Smet PA. Herbal remedies. New England Journal of Medicine. 2002;347(25):2046–2056. * Solomon PR, Adams F, Silver A, et al. Ginkgo for memory enhancement: a randomized controlled trial. Journal of the American Medical Association. 2002;288(7):835–840. * Ginkgo biloba. In: Coates P, Blackman M, Cragg G, et al., eds. Encyclopedia of Dietary Supplements. New York, NY: Marcel Dekker; 2005:249–257. * Ginkgo. Natural Medicines Comprehensive Database Web site. Accessed on July 2, 2007. * Ginkgo (Ginkgo biloba L.). Natural Standard Database Web site. Accessed on June 28, 2007. * Ginkgo biloba leaf extract. In: Blumenthal M, Goldberg A, Brinckman J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Lippincott Williams & Wilkins; 2000:359–366.
Originally published by NCCAM
National Institutes of Health
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