 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. Households Survey suggests as many as 2% of Americans are taking Ginkgo 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, hearty 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 Ginkgo leaves has become one of the most widely used herbal treatments for dementia. A 2009 Cochrane review of three dozen randomized controlled trials evolving 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 Ginkgo 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 Ginkgo leaf extract or placebo for five or six years to see if it would prevent them from sliding into dementia. Mild cognitive impairment is the intermediate clinical state between normal cognition for one's age and dementia. The conversion rate of MCI to dementia is about 10% per year. The bottom line? Neither trial showed any clear benefit, definitively demonstrating no preventative effect. However, for those already suffering with dementia, Ginkgo 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 Ginkgo in your Ginkgo supplements. Investigations of Ginkgo supplements off the shelves in both Europe and the U.S. found some that had no apparent Ginkgo at all, as high as about one in six Ginkgo supplements appeared to be all filler without any detectable Ginkgo bloba DNA. Side effects wise, typical doses such as 120 milligrams 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 Ginkgo, but thankfully this did not surface in systematic reviews of the dementia studies. Still, out of an abundance of caution has been recommended to stop taking Ginkgo supplements 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.