The world’s oldest living tree, dating back 250 million years, is the double-lobed leaves of the Ginkgo biloba tree. Close to 200 clinical trials have been published on ginkgo extract since 1980, with most of them supporting benefits related to improved circulation and mental function.
Sales of ginkgo have fluctuated over the years, and largely due to well-publicized studies published in the respected Journal of the American Medical Association.In 1997, a “gold standard” study like the ones used on pharmaceutical drugs – double-blind, placebo-controlled, randomized human clinical trial – was printed in JAMA. The year-long trial on 202 patients with mild to severe Alzheimer’s disease found changes that were “modest” but of “sufficient magnitude to be recognized by the caregivers. 1
This study led to ginkgo being the top-selling herb in the United States, as it is in Europe, where it has long been used to treat a range of conditions including memory and concentrationproblems, confusion, depression, anxiety, dizziness, tinnitus and headache.2
Ginkgo works by increasing blood supply by dilating blood vessels, reducing blood viscosity, modifying neurotransmitter systems and through antioxidant mechanisms. Standardized preparations contain 24 percent ginkgo flavonoid glycosides, six percent terpene lactones, and no more than five parts per million ginkgolic acids.3 The “24/6” numbers are most important, and these can be seen on labels of quality ginkgo bottles.
Ginkgo’s fortunes fell a bit in 2002 when a second study published in the Journal of the American Medical Association found “no measurable benefit in memory or related cognitive function to adults with healthy cognitive function.” The study on 230 men and women older than 60 years lasted six weeks.4
Today, ginkgo remains a top seller, and the National Institutes of Health gave ginkgo a grade of A for its positive influence on dementia and Alzheimer’s. JAMA has remained in the act, publishing in late 2009 results of a long-range ginkgo trial using the correct extract (EGb 761, aka 24/6), at a decent dose (120 milligrams twice daily). The people in the study ranged from 72 to 96 years old. Survey says: “No effect of the ginkgo biloba on these very slow, but clearly detectable, changes in thinking function in late life.”5
Herbalists noted that about 40 percent of patients dropped out during the six-year trial, certain cognitive parameters did not start being measured until a few years after the study’s start, the age of the subjects was quite advanced, and many were already taking a slew of pharmaceuticals that also could have confounded results.
And, as they say, one study does not make or break an ingredient, so the research will continue – as, no doubt, will ginkgo’s usage.
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