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The 1997 JAMA study was manna for the herbal supplements industry. The active ingredient in Ginkgold had, as the product's packaging now states, been "clinically proven." But EGb 761 had not been shown to improve mental functioning in healthy adults—only in elderly "demented" adults. This significant detail was conveniently elided in Ginkgold's marketing materials, as well as those of its competitors (many of which use as little genuine ginkgo as possible).
A 1991 French study found some positive effects among healthy young females, but it involved only 12 test subjects. Other studies using more volunteers offered inconsistent results—sometimes ginkgo improved memory very slightly, but the effects inexplicably faded in and out. A British researcher noticed that rats developed more brain receptors after ingesting ginkgo, but his findings "failed to meet the mathematical test for statistical significance."
In 2002, a long-anticipated paper appeared in JAMA titled "Ginkgo for memory enhancement: a randomized controlled trial." This Williams College study, sponsored by the National Institute on Aging rather than Schwabe, examined the effects of ginkgo consumption on healthy volunteers older than 60. The conclusion, now cited in the National Institutes of Health's ginkgo fact sheet, said: "When taken following the manufacturer's instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function."
The impact of this seemingly damning assessment, however, was ameliorated by the almost simultaneous publication of a Schwabe-sponsored study in the less prestigious Human Psychopharmacology. This rival study, conducted at Jerry Falwell's Liberty University, was rejected by JAMA, and came to a very different—if not exactly sweeping—conclusion: There was ample evidence to support "the potential efficacy of Ginkgo biloba EGb 761 in enhancing certain neuropsychological/memory processes of cognitively intact older adults, 60 years of age and over." The two studies canceled each other out in the court of public opinion; ginkgo sales remained strong.
Conflicting views of ginkgo's memory-enhacing properties are likely inevitable, since it's difficult to measure mental acuity: Every study must rely to some extent on volunteers' impressions as to whether their memories have improved. Analyze enough small sets of such subjective data and you're bound to find evidence to support either position. And if you come down a skeptic, be careful—Schwabe recently sued an Australian consumer watchdog to prevent it from publishing a report critical of EGb 761.
A large-scale, multicenter, multiyear study might clear things up, but no one appears interested in funding such a massive effort. The National Center for Complementary and Alternative Medicine is in the midst of a clinical trial involving 3,000 Alzheimer's patients, but this obviously has no bearing on whether ginkgo can help the healthy.
Regardless, herbal companies will continue to advertise their ginkgo supplements with such watery, asterisked statements as, "May help to support mental sharpness." Starbucks, of course, could reasonably make the same claim.