Whether your memory loss is isolated to a recent, foggy patch between New Year's Eve and noon the next day, or whether it is more profound, popping ginkgo biloba to enhance your recollection or any other cognitive function might be of little value.

In the largest study to date, U.S.-based researchers have found no evidence that daily ginkgo supplements slow the rate of cognitive decline or dementia in older adults. The study, published in the Dec. 23/30 issue of the Journal of the American Medical Association, was a randomized, double-blind, placebo-controlled clinical trial of more than 3,000 adults aged 72 to 96 who were followed for for six years on average.

This same study, called the Ginkgo Evaluation of Memory (GEM) study, had found in 2008 that ginkgo supplements were not effective in reducing the incidence of Alzheimer dementia or dementia overall.

While the results do seem damning — the authors of the JAMA article indeed conclude that there's no reason to take ginkgo other than blind faith — this won't be the last word on the herb's usefulness. Cognition is too complicated and studies have been too short to rule out long-term use for a middle-age adult to prevent mental decline.

History worth remembering

Ginkgo leaves and seeds have been used medicinally for centuries in Chinese traditional medicine for all types of ailments, from gout to gonorrhea. Like aspirin, ginkgo can reduce blood clotting and improve circulation. And also like aspirin, it does little for gout or gonorrhea.

Ginkgo become popular in the West in the 1980s when a German company called Dr. Willmar Schwabe Pharmaceuticals began manufacturing a high-quality extract for the European and U.S. markets. Nature's Way, a U.S.-based dietary supplement maker, carries Schwabe's patented formula under the name Ginkgold, one of the company's best-selling products.

Ginkgo has promising medicinal properties, and many scientists were initially excited by its potential. By 1997 things were looking good for ginkgo advocates. JAMA published the results of a yearlong study of about 200 adults, albeit supported by Schwabe Pharmaceuticals, which found that ginkgo improved cognitive performance — and so begot the words "clinically proven" adorning bottles of ginkgo biloba extract.

Few studies have been able buoy these claims, though. A slightly larger but shorter study (not supported by Schwabe Pharmaceuticals) published in JAMA in 2002, found no benefit for memory or cognitive function. Curiously, a Schwabe-supported study of almost the exact same size and duration published almost exactly the same time in a minor journal called Human Psychopharmacology, led by a scientist at Jerry Falwell's Liberty University, found, well, you guessed it: Ginkgo works.

The news media followed accordingly, reporting mixed results; and ginkgo's popularity continued to grow.

History worth repeating

Here we are eight years later with another curious battle between JAMA and Human Psychopharmacology. Schwabe Pharmaceuticals posted a press release on its website last month titled "Ginkgo biloba extract is effective for cognitive decline," highlighting the results of a July 2009 article in Human Psychopharmacology called "Ginkgo biloba: specificity of neuropsychological improvement — a selective review in search of differential effects."

As the journal article title suggests, this analysis cherry-picks 29 studies from 1980 to 2007 with a total of 2,414 participants for an entirely different purpose: not to see if ginkgo works but rather identify characteristics of reported benefits. Schwabe Pharmaceuticals didn't fund the study.

Schwabe, naturally, isn't thrilled with the new JAMA article that concludes ginkgo doesn't help memory, calling it "methodologically so weak that it is of limited relevance," in a Dec. 29 statement. Schwabe's Jochen Mühlhoff raised several legitimate points in an e-mail to LiveScience: namely that the rate of cognitive decline across the study, even in the placebo group, was "extraordinarily slow" — too small to distinguish adequately — and that the study would have to run another 10 years for "relevant mental decline" to be evident.

Also, as noted in the study, about 40 percent of the participants weren't taking ginkgo or the placebo regularly by the end of the study.

With ginkgo's purported effectiveness so entrenched in our collective memory, it's unclear whether the most recent JAMA article will dent sales. Those who believe in and eagerly consume ginkgo biloba may, perhaps ironically, forget about latest batch of bad news. Remember you heard it here first.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears each Tuesday on LiveScience.