The popular Chinese herb ginkgo biloba is promoted as a treatment for circulatory disorders and cognitive problems and as a preventive for dementia. Despite the lack of convincing evidence of benefits, the extract is an ingredient in countless supplements, especially brain and memory formulas.
At least it appeared to have few serious side effects other than an increased risk of bleeding, which could be a problem for people on warfarin (Coumadin) or other blood thinners.
However, a new government toxicology study found “consistent” evidence that ginkgo extract causes cancer in rodents. What happens to lab animals given very large doses of a substance may not happen in humans, of course, but such toxicity studies are a mainstay in evaluating cancer risk and, at the very least, raise a red flag.
Add that to the disappointing research on ginkgo’s purported benefits (including a recent review on ginkgo as a treatment for tinnitus), and you would be wise to steer clear of supplements containing the herb.