If asked to name the top 5 or 10 herbs and phytomedicines that are the most clinically tested, most knowledgeable herb researchers would most likely include the standardized extract of ginkgo leaf (Ginkgo biloba) as an obvious candidate. There are probably more than 140 published clinical trials documenting the safety and efficacy of the two leading German ginkgo extracts (or Ginkgo biloba extract, GBE) for a variety of indications, the leading brand known as EGb 761 (W. Schwabe, Karlsruhe, Germany) and the next being LI 1370 (Lichtwer Pharma, Berlin).

So it was a big surprise, and disappointment, to many herb researchers and advocates when in August 2002 a negative trial on a leading ginkgo preparation was published in the Journal of the American Medical Association.¹ On August 20 all three major TV network newscasts ran the story—with Brokaw, Jennings, and Rather speaking as if they understood what they were reporting—complete with a video news release supplied by the AMA. Their message was pretty much the same—forget about ginkgo! The story was also carried in almost all of the next day’s newspapers and other media worldwide.

The trial tested the memory and concentration of normal healthy older adults, and was modeled after what the researchers said was the way GBE was being marketed, i.e., it was being promoted to improve memory and concentration for normal people in everyday tasks (memorizing shopping lists, etc.). The product tested was the leading US ginkgo supplement containing the most highly-researched German extract, and the dose was 120 mg per day, just as promoted on the company’s Web site.

The way the results were misrepresented in the media, the general message tended to say that there was no basis for the use of GBE by anyone, for any reason. Never mind that most GBE trials measuring mental functions have been conducted on subjects with cognitive impairment and early stages of Alzheimer’s dementia, and the evidence for its safety and efficacy in such subjects is compelling. A few months later, the Cochrane Collaboration and the Alzheimer’s Society of England concluded that there were 33 randomized trials that showed “promising evidence” for the use of GBE in early stages of Alzheimer’s dementia, a finding that was ignored in the US media, despite a press release from us.²

Of course, the safety and efficacy of any substance cannot be fully evaluated by the results of just one trial. Just prior to the publication of the Solomon study in JAMA, a similar trial was published in a psychopharmacology journal.³ Using a dosage of 180 mg of the same German extract used in similar tests, this trial yielded positive results.

We contacted W. David Crews, Jr., PhD, the co-author of the positive trial, and suggested that he and his colleagues write a comprehensive review of all clinical trials using GBE to test cognitive functions in normal healthy adults. At the time he was too busy to produce such a paper, but last November he sent us an initial draft of his systematic review of these trials. After several rounds of editing and peer review by several experts on this subject, we are publishing Dr. Crews and his team’s review of 16 published trials on GBE in normal, healthy adults. We offer this extensive paper in this issue to help clarify the record. The results show that there is a growing body of evidence in published trials supporting the safety and efficacy of GBE for improving memory, concentration, and speed in processing mental functions in non-cognitively impaired adults. As stated by the authors themselves, “some of the most common positive neuropsychological effects found for GBE across the acute and short- to long-term studies involving healthy/cognitively intact participants have been enhanced performances on tasks assessing aspects of memory, attention, and speed of processing abilities.”

References

1. Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement: a randomized controlled trial. JAMA. 2002;288:835-840.

2.Scientific review of ginkgo finds “Promising Evidence” in improving memory in older patients with dementia [press release]. Austin, TX: American Botanical Council, December 10, 2002.

3. Mix JA, Crews WD Jr. A double-blind, placebo-controlled, randomized trial of Ginkgo biloba extract EGb761in a sample of cognitively intact older adults: neuropsychological findings. Hum Psychopharmacol Clin Exp. 2002;17:267-277.