Ginkgo biloba is the world’s oldest living species of tree. Individual trees live as long as 1,000 years. Ginkgo grows most predominantly in the southern and eastern United States, southern France, China, and Korea. Medicinal use of ginkgo can be traced back almost 5,000 years in Chinese herbal medicine. The nuts of the tree were most commonly recommended and used to treat respiratory tract ailments. The use of the leaves is a modern development originating in Europe.

The medical benefits of Ginkgo biloba extract (GBE) are attributed primarily to two groups of active constituents: the ginkgo flavone glycosides and the terpene lactones. Ginkgo flavone glycosides, which typically make up approximately 24% of the extract, are primarily responsible for GBE’s antioxidant activity and may mildly inhibit platelet aggregation (stickiness). These two actions may help GBE prevent circulatory diseases, such as atherosclerosis, and support the brain and central nervous system. Ginkgo is also well-known for its effect on memory and thinking (cognitive function). It may enhance cognitive performance in healthy older adults, in people with age-related cognitive decline, and in people with Alzheimer’s disease.

Most clinical trials have used between 120 and 240 mg of GBE (standardized to contain 6% terpene lactones and 24% flavone glycosides) per day, generally divided into two or three portions. The higher amount (240 mg per day) has been used in some people with mild-to-moderate Alzheimer’s disease, age-related cognitive decline, intermittent claudication, and resistant depression. GBE may need to be taken for eight to twelve weeks before desired actions such as cognitive improvement are noticed. Mild headaches lasting for a day or two and mild upset stomach have been reported in a small number of people using GBE.

Clinical trials of ginkgo supplementation have found no significant adverse effects after as many as 12 months of supplementation. People should seek an accurate medical diagnosis prior to self-prescribing GBE. This is especially important for the elderly, whose circulatory conditions can involve serious disease, and for people scheduled for surgery, as GBE may affect bleeding time.