Thursday, January 7, 2010

Can Ginkgo Biloba Prevent or Slow Down Alzheimer's Symptoms

Ginkgo biloba is a plant extract containing several compounds that may have positive effects on cells within the brain and the body. Ginkgo biloba is thought to have both antioxidant and anti-inflammatory properties, to protect cell membranes and to regulate neurotransmitter function. Ginkgo has been used for centuries in traditional Chinese medicine and currently is being used in Europe to alleviate cognitive symptoms associated with a number of neurological conditions.

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The difficulty of stating absolutes about ginkgo's effectiveness is that research findings vary in their results. Some clinical trials do show some small positive effects on people with Alzheimer's disease, other studies no effect.

Gold, Carhill and Wenk (2003) say in their prospective study (extensive review) that, "Our overriding impression, however, is that we do not have enough information to say conclusively whether ginkgo does or does not improve cognition".

The final results of a large, multicenter Phase III study published in the Journal of the American Medical Association  (November 19, 2008) has also showed that gingko was no better than placebo in delaying changes in memory, thinking and personality and had no impact on the development of dementia and Alzheimer’s.

The Gingko Evaluation and Memory (GEM) Study enrolled 3,000 individuals age 75 or older who either had no dementia or mild cognitive impairment. Participants were randomly assigned to receive twice daily doses of either a placebo or 120 milligrams of gingko biloba extract. They were followed up every six months for six years.

Researchers found no statistical difference in dementia or Alzheimer’s rates between the groups. Among those receiving gingko, 277 developed dementia. Among those receiving placebo, 246 developed dementia. Mortality rates were also similar.

"It just continues to show that in properly designed, placebo-controlled studies, we can't seem to find an effect for ginkgo biloba," says Lon Schneider, an Alzheimer's and gerontology expert at the University of Southern California. The size of this study is larger than all previous ginkgo biloba studies combined, he says.

Douglas MacKay, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a supplement industry trade group, disputes the study's findings.
"There is a large body of previously published evidence, as well as ongoing trials, which suggest that ginkgo biloba is effective for helping to improve cognitive impairment in older adults," he says.

U.S. sales for ginkgo biloba were $99 million in 2008, down 8% from 2007 but still placing it the 8th most popular herb and botanical that the Nutrition Business Journal tracks.

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Is Ginkgo Harmless?
The findings strongly argue against the use of ginkgo biloba for the prevention of mental decline in older populations, claims professor Lon S. Schneider, MD from University of Southern California psychiatry and neurology. He notes that the GEM study is far larger and longer than any previous placebo-controlled ginkgo biloba trial. "The message to take from this is that this intervention doesn't work," he says.

In an editorial accompanying the study, Schneider pointed to earlier trials suggesting a slight increase in strokes and mini-strokes in patients taking ginkgo biloba.

In the GEM study, there was no difference in heart attack or ischemic strokes between the ginkgo and placebo-treated patients. Ischemic strokes, the most common type of stroke, are caused by a blockage in an artery that supplies blood to the brain. There were more hemorrhagic (bleeding) strokes in the ginkgo group, but the overall number of cases was small and the difference was not found to be significant.

"The potential adverse effects of ginkgo biloba extract illustrate why it is untenable to recommend a drug or nutraceutical in the absence of efficacy evidence simply because it could possibly help and initially appears harmless," Schneider writes.

Although he acknowledges that the GEM study was well designed, Mark Blumenthal, who is founder and executive director of the American Botanical Council, tells that the trial does not represent the last word on ginkgo biloba and dementia.

"There are other trials that will be coming out," he says. "Whether or not they will show a positive result or not remains to be seen." He cited several studies suggesting a role for ginkgo biloba in slowing the progression of dementia in elderly people already experiencing cognitive decline. "In reporting the news that ginkgo biloba didn't work for prevention in this study, it is important not to mislead people into thinking that there is no evidence to support treatment," he says.

About Ginkgo Biloba
Ginkgo Biloba is sometimes called a living fossil and the only surviving member of the Ginkgo family. It is one of the oldest living tree species, a deciduous conifer, dating back over three-hundred million years. Individual trees may live for one thousand years, as they are resistant to viruses, fungi, insects, pollution and even radiation, and they may reach 122 feet in height. Native to China, it has been included in Chinese herbal medicine's repertoire for almost five thousand years, where it was used for respiratory tract ailments and for memory loss in older adults. The trees were introduced to Europe in 1730 and the United States in 1784 as ornamentals, but since the 1980s, Western medical interest in the plant has grown dramatically since its potent actions on the cardiovascular system were identified. Different parts of the plant have different properties with different medical applications. Most commercial growth of Ginkgo is centered in plantations in South Carolina, France and China. Some of Ginkgo's constituents include amino acids, tannins, quercetin, beta-carotene, flavone glycosides, bioflavones, sitosterol, lactones, anthocyanin, calcium, iron, magnesium, manganese, phosphorus, potassium, zinc, B-vitamins and vitamins A and C. Ginkgo is now among the leading prescription medicines in both Germany and France

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