A centuries-old Chinese herbal medicine, ginkgo comes from the dried leaves of the maidenhair tree (Ginkgo biloba). It contains a complex mix of compounds, but researchers have primarily focused on two particular chemical groups—flavonoids and terpenoids. Like aspirin, ginkgo can keep blood clots from forming and may increase blood flow.
A standardized extract developed in Germany, EGb761, is the form used in many clinical trials and is widely prescribed there for “dementia-related syndrome” and in France for “cerebral insufficiency,” which can mean anything from confusion and depression to memory impairment and dementia. It’s also used for circulatory disorders, such as intermittent claudication (pain in the legs due to obstructed blood flow).
Claims, purported benefits: Improves blood flow and improves circulatory dis- orders, reduces blood clotting, has anti-inflammatory, antioxidant, and neuroprotective effects. Treats eye diseases and tinnitus. Many people take ginkgo in hopes that it will sharpen their memory and concentration.
What the science says: There is moderate evidence that ginkgo can help treat dementia, but not prevent it. Fifteen years ago, a widely publicized study found that ginkgo improved mental functioning in people with Alzheimer’s. But a review of 35 studies by the Cochrane Collaboration in 2007 concluded that the overall evidence for ginkgo as a treatment for dementia or cognitive impairment is “inconsistent and unconvincing.” Since then, many more studies have been done.
A 2014 review of seven clinical trials in Clinical Investigations in Aging found that the EGb761 extract is at least modestly effective in people with dementia, as did a 2015 review of 15 trials in the Journal of Pharmaceutical Health Care and Sciences. And still another review, in the Journal of Alzheimer’s Disease in 2015, looked at nine clinical trials and concluded that EGb761 can stabilize or slow decline in cognition and function in those with impairment or dementia.
As for prevention trials, a large, well-designed study of healthy people 75 and older in 2008 found no evidence that ginkgo helps prevent dementia, including Alzheimer’s. In 2009, a follow-up study in the Journal of the American Medical Association found that the supplement did not slow cognitive decline or memory loss in any way. In 2012, a well-designed French study in Lancet Neurology looked at 2,850 people aged 70 and older with self-reported memory complaints, half of whom took the EGb761 extract twice daily, half a placebo. After five years, ginkgo did not slow the rate of progression to Alzheimer’s.
As for treating tinnitus, a research review by the Cochrane Collaboration in 2013 concluded that the limited evidence about ginkgo does not demonstrate that it is effective for this purpose.
Common side effects: Because some cases of ginkgo-related bleeding have been reported, it should be avoided before surgery and used cautiously with aspirin, warfarin (Coumadin), or other drugs that affect blood clotting. The herb may increase the sedative effects of certain antidepressants or increase blood concentrations of some drugs used for treating hypertension. Rare side effects include headache, stomach upset, palpitations, dizziness, and rashes.
Our advice: Though ginkgo is one of the best-studied herbs, there is no convincing evidence it has any effect on memory or other mental functions in healthy older people—or that it has any health benefits, period. Add that to the safety questions, and you would be wise to steer clear of supplements containing the herb. Still, if you or a family member has Alzheimer’s or another dementia, you might talk to your doctor about trying ginkgo. Furthermore, commercially available products may be different from the preparations used in clinical studies, so you may not get the same effects. Some ginkgo supplements sold in the United States claim to be the standardized extract used in research, but you can’t be sure.