Ginkgo Biloba as a Brain Health Supplement for Dementia

More than a third of older Americans take some kind of “brain health supplement” to the tune of billions of dollars a year, and one of the most popular is Ginkgo biloba. U.S. household surveys suggest as many as 2 percent of Americans are taking gingko supplements. Ginkgo biloba is a tree with fan-shaped leaves, regarded as a living fossil, having persisted relatively unchanged for over a quarter billion years. Its resilience makes it a favorite of urban planners—hardy enough to survive even a nuclear blast (as one of the few survivors within a short radius of ground zero in Hiroshima).

Over the last 30 years or so, an extract of gingko leaves has become one of the most widely used herbal treatments for dementia. A 2009 Cochrane review of three dozen randomized controlled trials involving more than 4,000 participants concluded that the “evidence that Ginkgo biloba has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unreliable.” One trial showed very large benefits, but others showed no effect at all. To put the subject to rest once and for all, two large randomized, double-blind, placebo-controlled trials were conducted, one in Europe, funded by a gingko supplement manufacturer, and the largest, longest study to date, funded by the NIH in the United States. More than 5,000 older men and women with either normal cognition or mild cognitive impairment were randomized to a gingko leaf extract or placebo for five or six years to see if it would prevent them from sliding into dementia. (Mild cognitive impairment (MCI) is the intermediate clinical state between normal cognition for one’s age and dementia.) The conversion rate of MCI to dementia is about 10 percent per year. The bottom line: Neither trial showed any clear benefit definitively demonstrating no preventative effect.

However, for those already suffering with dementia, gingko leaf extracts do appear to slow cognitive decline compared to placebo for those with Alzheimer’s or dementia more broadly defined. Of course, that’s assuming there’s actually gingko in your gingko supplements. Investigations of gingko supplements off the shelves in both Europe and the U.S. found some that had no apparent gingko at all. As high as about one in six ginkgo supplements appeared to be all filler, without any detectable Ginkgo biloba DNA.

Side effects-wise, at typical doses, such as 120 mg twice a day, ginkgo extracts may cause mild stomach upset, headache, dizziness, constipation, and allergic skin reactions. Higher dosages can result in restlessness, diarrhea, nausea, vomiting, and weakness. There have been about a dozen published case reports of bleeding associated with gingko; but thankfully, this did not surface in systematic reviews of the dementia studies. Still, out of an abundance of caution, it has been recommended to stop taking gingko supplement at least two weeks before elective surgery.

The bottom line, according to a recent review of Alzheimer’s disease therapies, is that ginkgo is one of the few things that can beat out placebo for cognitive function.