August 19, 2002 (Austin, TX).
Impressive evidence in the scientific and clinical literature supports the benefits and safety of the popular herb ginkgo, according to the nonprofit American Botanical Council (ABC). The information from ABC comes at the same time as a new study published in the Journal of the American Medical Association (JAMA) in which ginkgo extract did not increase mental function in normal, healthy older patients.* The six-week randomized study tested healthy adults for learning, memory, attention, concentration, and verbal fluency using the standard dose of 120 mg ginkgo extract per day. The study was conducted by researchers at Williams College in Williamstown, Massachusetts.
"The value of ginkgo or any dietary supplement cannot be determined on the basis of one study alone," said Mark Blumenthal, founder and executive director of ABC. "There are more than 125 clinical trials published on ginkgo extract over the past two decades, with most of them supporting numerous important benefits related to improved circulation and mental function."
Blumenthal added that several recent articles reviewing the medical literature have supported the cognitive (mental) benefits of ginkgo in patients with early stages of dementia, and a one-year study published in JAMA in 1997 supported the benefits of using ginkgo to retard the progression of symptoms in early stages of Alzheimer’s disease. Several recent studies have also shown cognitive benefits of ginkgo in healthy older adults, he added. In one study recently published in Human Psychopharmacology using a similar design with a higher dosage (180 mg per day), researchers observed clinically significant cognitive benefits in healthy individuals.**
There are dozens of positive clinical studies for ginkgo for cognitive disorders published in the scientific literature. Thirty-four clinical trials on ginkgo are summarized in an extensive monograph (technical paper) for healthcare practitioners in ABC’s forthcoming new book, The ABC Clinical Guide to Herbs. All but two show positive benefits for memory and other mental functions, and for peripheral arterial occlusive disease, a condition characterized by pain in leg muscles during walking affecting many older adults. Other potential benefits suggested by several clinical studies include improved performance of hikers susceptible to lack of oxygen in high altitudes (mountain sickness), and male and female sexual dysfunction.
In 1994 the respected Commission E, the agency that approves the safety and efficacy of herbal medicines in Germany, considered the scientific and clinical information on ginkgo to be strong enough to approve ginkgo extract as safe and beneficial in treating certain cognitive and circulatory disorders, according to Blumenthal, who is also the senior editor of an English translation of the Commission E’s monographs.
One potential question about the new study is the important research protocol of "blinding" the samples, so that neither the patients nor the researchers are able to distinguish test substances from placebos. The paper in JAMA noted that the placebo or dummy pills were made of gelatin capsules, while the actual ginkgo product is a small, coated tablet. Whether this made any significant difference in maintaining the blinding necessary to be classed a "double-blind" trial is not yet determinable, said Blumenthal.
A rational perspective on the significance of the new study is provided by psychopharmacologist Jerry Cott, Ph.D., an expert on dietary supplements and drugs that affect the mind and nervous systems: "It is very difficult to improve cognition in a normal person; it’s much easier to improve in an impaired person. That is, normal functioning in a healthy person is like an upper limit; a person is already doing as well as can be expected. It is therefore very difficult to measure improved mental performance without a precise objective measurement scale."
Hyla Cass, M.D., a psychiatrist and author in Los Angeles who successfully uses ginkgo in her clinical practice, expressed concern about the impact of the publicity that may be generated on the new clinical trial. "Heavy promotion of the outcomes of this study may result in a disservice to the public. It can turn people away from a safe, well-researched product that previous research has proven can improve their quality of life," she explained. Dr. Cass has also found ginkgo to be helpful in treating male sexual dysfunction that has declined with age (often due to impaired circulation), a well as sexual problems associated with the use of certain types of antidepressant drugs.
Ginkgo preparations are made from the leaf of the ginkgo tree (Latin name Ginkgo biloba), the world’s oldest living tree, dating back 250 million years. Ginkgo trees were found living in China and northern Japan, and are now grown for commercial cultivation in the U.S. and other countries. Extracts from ginkgo leaves are pharmaceutically concentrated and standardized to some of ginkgo’s unique biologically active chemical compounds. The leading most well-researched ginkgo extract from Germany is licensed as a medicine in many countries worldwide. Ginkgo is also the top-selling herbal dietary supplement in the U.S. for the past five years, according to information in ABC’s peer-reviewed journal, HerbalGram.
The American Botanical Council is the nation's leading nonprofit organization addressing research and educational issues regarding herbs and medicinal plants. The 13-year-old organization occupies a 2.5 acre site in Austin, Texas where it publishes HerbalGram, a peer-reviewed journal on herbal medicine, and will publish a forthcoming book and continuing education course for healthcare professionals, The ABC Clinical Guide to Herbs, containing an extensive science-based monograph on the safety and efficacy of ginkgo. Information contact: ABC at P.O. Box 144345, Austin, TX 78714-4345, ph: 512-926-4900, fax: 512-926-2345. Website: www.herbalgram.org.
*Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement: A randomized controlled trial. JAMA 2002;288(7):835-40.
** Mix JA, Crews WD. A double-blind, placebo-controlled, randomized trial of Ginkgo biloba extract EGb 761 in a sample of cognitively intact older adults: neuropsychological findings. Human Psychopharmacol Clin Exp 2002;17:267-77.