Ginkgo is derived from the leaves of the ginkgo tree (commonly planted for ornamental purposes). The leaves contain numerous biologically active substances. Ginkgo is one of the most commonly used herbal supplements.
The fruit of the ginkgo tree is not used in ginkgo products. Contact with the fruit pulp, which may be encountered under ginkgo trees, can cause severe skin inflammation (dermatitis). The seeds of the fruit are toxic and can cause seizures and, in large amounts, death.
Ginkgo reduces the clotting tendency of particles in the blood that help stop bleeding (platelets), dilates blood vessels (thereby improving blood flow), and reduces inflammation. People take ginkgo for many reasons, such as improving blood flow to the lower legs in people with atherosclerotic vascular disease of the arteries in the legs (peripheral arterial disease) and treating dementia (as in Alzheimer’s disease). Scientific studies clearly show ginkgo benefits people with peripheral arterial disease. Ginkgo increased the distance that affected people could walk without pain. Benefit for people with dementia seems unlikely based on findings from a large clinical trial. In this clinical trial, ginkgo was not effective in reducing the development of dementia and Alzheimer’s disease in older people. However, a previous large U.S. clinical trial indicated that ginkgo temporarily stabilized mental and social function in people with mild to moderate dementia.
Studies show ginkgo does not seem to alleviate memory loss, ringing in the ears (tinnitus), or altitude sickness. Ginkgo may prevent damage to the kidneys caused by the drug cyclosporine, which suppresses the immune system.
Although ginkgo leaf extracts usually have no side effects except mild digestive upset, the use of ginkgo should be supervised by a doctor because it is not suitable for self-medication. Ginkgo may interact with drugs that prevent blood clots, aspirin, and other nonsteroidal anti-inflammatory drugs (NSAIDs). It may increase the risk of bleeding, although a large clinical trial found no evidence for increased risk of bleeding among people taking ginkgo. Ginkgo may also reduce the effectiveness of anticonvulsants.