Last month, a report in the Journal of the American Medical Association showed that the herbal supplement Ginkgo biloba does not appear to help memory or slow the rate of cognitive decline in healthy older people.

On Yale neurologist Steven Novella’s “Science-Based Medicine” Web site he explained, “The study was a direct comparison of Gingko biloba at 120 mg twice a day versus placebo—a double blind, randomized, multi-center trial involving 3,019 subjects aged seventy-two to ninety-six, followed for a median of 6.1 years. Subjects were followed with standardized tests of cognitive function. The results are easy to report: every measure showed no difference between Gingko biloba and placebo. There was no difference in cognitive function, risk of developing dementia, rate of progression of dementia, or normal cognitive decline with aging.”

Gingko biloba is one of the world’s top-selling herbal supplements, widely advertised as having been proven effective in helping people increase memory and concentration. The fact that study after study has shown it is not effective comes as a blow to the herbal industry, but new research suggests that Gingko may actually harm some people.

According to new study in the Journal of Natural Products “restrictions should be placed on the use of Ginkgo biloba because of growing scientific evidence that Ginkgo may increase the risk of seizures in people with epilepsy and could reduce the effectiveness of anti-seizure drugs.”

Researchers Eckhard Leistner and Christel Drewke reviewed scientific research on Ginkgo, and found 10 reports indicating that patients with epilepsy who take Ginkgo products face an increased risk of seizures. Ginkgotoxin, a component of Gingko biloba, seems to alter a chemical signaling pathway in ways that may trigger epileptic seizures. Ginkgo may also interact with anti-seizure medications and reduce their effectiveness. “We are now convinced… that G. biloba medications and other products can have a detrimental effect on a person’s health condition,” the report concludes.

Herbal supplements and remedies are not marketed as drugs (note the paragraph of legal fine print on bottles starting with, “This product is not intended to diagnose, treat, cure, or prevent any disease.”) That’s because in many cases the drugs have not been scientifically tested for safety or efficacy. They have not been proven to work in carefully-controlled clinical trials.

The herbal supplement industry is a multi-billion dollar business, and has lobbied hard to keep their products from being regulated by the FDA. As a result, the FDA can only step in when something goes wrong, after people have been injured or killed by natural herbs.

That’s just what happened in 2004, when the FDA banned ephedra, an herbal remedy used in traditional Chinese medicine for thousands of years. Millions of consumers took the herb, on the belief that it was natural, safe, and effective. The herb was widely used for treating everything from the common cold to asthma to weight loss. Then the herb was linked to over 100 deaths; healthy people who took ephedra had a wide range of symptoms ranging from insomnia to heart attacks.

Now it seems another natural herbal remedy may pose a hidden danger. All drugs, whether pharmaceutical or “natural,” can have dangerous and unintended side effects. But when people are harmed or killed by an herbal supplement that has never been shown to work in the first place, the situation is all the more tragic.