Gingko biloba is a common Asian tree that grows in much of North America. In Chinese medicine, the fruit of the gingko plant is used to treat certain lung disorders. Preparations isolated from the seed may be helpful in fungal, bacterial and viral infections. Gingko biloba may also help increase blood circulation and is widely used in Europe to treat conditions associated with atherosclerosis (hardening of the arteries) and memory loss in the elderly. (Brain and nerve cells are especially vulnerable to the restriction of blood and oxygen flow.) The plant is also used to treat depression and impotence arising from circulation problems. It is recognized as an antioxidant, meaning it helps neutralize free radicals - those highly active molecules that can cause damage to the body.

Although the use of gingko to treat AIDS-related dementia has not been studied, many HIV-positive people use it to treat and prevent this condition as well as memory loss. Studies on people who have had strokes or suffer from Alzheimer's disease have shown that ginkgo significantly improves the symptoms of memory loss and confusion. Studies on animals have shown that it can reduce certain types of tissue damage resulting from a stroke.

Because of its popularity in Europe, gingko has been widely studied. (It accounts for more than one per cent of all prescriptions written in France and Germany.) In the over 1,000 people included in a review of such trials, side effects were very rare -- stomach upset and headaches were the most common. Gingko is used to treat circulation problems because it prevents platelet clumping. For this reason, it may be dangerous for people with low platelets or problems with nose bleeds or heavy menstruation. Several case studies have reported spontaneous bleeding in people using ginkgo. Ginkgo biloba extract is usually sold in capsules or tablets standardized to 24 per cent ginkgo heterosides (also called flavone glycosides). Gingko seeds are toxic and should not be consumed.