Background information
Ginkgo is thought to be the oldest tree on the planet, first growing about 200 million years ago. Its reputation as an "anti-ageing" herb seems to be appropriate. Gingko biloba's effects on memory, brain function, and circulation have made this venerable tree one of the most extensively studied and widely used botanicals in the world. Strong clinical evidence shows that it can help improve declining brain function in elderly people, even those with Alzheimer's disease (McCaleb et. al., 2000).
 
History and folk use
Use of gingko medicinally can be traced back almost 5000 years, to the origin of Chinese medicine. Gingko was first introduced by Chen Noung (2767-2687 BC) in the first pharmacopoeia, Chen Noung Pen Tsao. It was recommended for memory loss in the elderly and respiratory tract ailments (Brown, 1996). 
 
Parts used
The leaves of younger trees. Common uses:

• Memory loss associated with ageing
• Early stages of Alzheimer's disease
• Poor circulation to the extremities; intermittent claudication
• Long-term recovery from a stroke
• Tinnitus (ringing in the ears) and hearing loss (Brown, 1996) 

Popularity
Ginkgo is among the most frequently prescribed herbal medicines all over the world. It’s prescribed for the treatment of health conditions that include depression, stroke, intermittent claudication, vertigo, tinnitus, multiple sclerosis, and impotence. But ginkgo’s primary claim to fame is its ability to help with memory and related brain functions. Ginkgo is the best selling herbal medicine in France and Germany, where it’s taken by millions of people from middle age onwards to maintain and improve cerebral circulation and to reduce the possibility of a stroke. It’s probably one of the most useful herbs for the treatment of senile dementia (Chevallier, 1996). 
 
Active constituents

• Gingko flavone glycosides (bioflavonoids)
• Terpene lactones - ginkgolides and bilobalide (Brown, 1996) 

Recommended use

• About 50 to 75 pounds of leaves to form 1 pound of concentrated ginkgo biloba extract (Milam, 1997)
• Standardised extract containing 24% ginkgo flavone glycosides and 6% terpene lactones - 120 to 240mg daily, divided in two to three doses (Brown, 1996; Milam, 1997; Bratman et al, 1999; Murray, 1995)
• In most clinical studies, the effective dosage of standardized extract was about 40mg three times a day, approximately 120mg of ginkgo leaf extract daily (McCaleb, 2000). 

How it works
Ginkgo's most powerful effect is on the circulatory system. By regulating the tone and elasticity of blood vessels, ginkgo extract increases blood flow to the brain, central nervous system (CNS) and extremities, making it particularly useful and popular for circulatory ailments. As a powerful antioxidant, it mops up the damaging compounds known as free radicals, hence aiding in cell maintenance, in the brain and nervous system. Specifically, the functions of ginkgo include:

• Antioxidant properties - Numerous studies demonstrate that ginkgo biloba extract exerts antioxidant activity in the brain, retina, and cardiovascular system. Its antioxidant activity in the brain and CNS make it an extremely promising herb for prevention of age-related declines in brain function (Brown, 1996). Such antioxidant properties also help strengthen blood vessel walls and improve their overall tone and elasticity. This in turn contributes to flexible and improved flow of blood to tiny capillaries in the brain, eyes, ears, limbs and other parts of the body (McCaleb et al, 2000).
• Dilation of blood vessels - Ginkgo flavenoids directly dilate the fine vessels of the circulatory system, the micro-capillaries, which increase both blood circulation and oxygen levels in the brain, as well as other critical organ tissues. It has been shown that oxygen-rich blood enhances the memory (Milam, 1997).
• Increased ability of brain to utilise glucose - Glucose is a carbohydrate the brain uses for fuel. It has been shown that ginkgo can enhance the ability of brain cells to make use of glucose. With improved energy levels, the brain is supplied with required fuel to perform better. Improved mental alertness - It has been shown that ginkgo increases the rate at which nerve cell impulses occur. Increased speed of nerve signal transmission equates to an increase in mental sharpness or alertness.
• Inhibiting Platelet Activating Factor, or PAF, is a mediator released from cells that causes platelets to aggregate (clump together). Excessive amount of PAF may lead to the formation of blood clots (thrombosis) within the circulatory system, potentially resulting in heart disease, strokes and intermittent claudication or painful walking. Numerous studies have confirmed that ginkgo biloba extract is an extremely effective agent for inhibiting PAF's (Milam, 1997). 

Health applications of Ginkgo Bilboa

• Cerebrovascular insufficiency - This implies a reduction in blood flow to the brain. Clinical studies show that daily doses of 120 to 240mg of ginkgo biloba extract (taken in two to three divided doses) lead to an improvement in the symptoms associated with cerebrovascular insufficiency, such as memory loss, depression, and tinnitus within 8 to 12 weeks (Brown, 1996).
• Alzheimer's disease - This condition is closely linked to the lack of adequate blood flow within the brain caused by poor circulation or other vascular disease. While ginkgo is not a cure for Alzheimer's disease, it's emerging as a potential tool to slow the progression in the early stages. A 1997 study involving 309 people demonstrated that treatment with standardized ginkgo extract helped improve or stabilize a number of daily living and cognitive functions in elderly patients with mild to severe dementia due either to Alzheimer's disease or multi-infarct dementia (McCaleb, 2000).
• Resistant depression - Reduction in blood flow to the brain has been clearly established in many depressed individuals over the age of 50 years. Using a daily dose of 240mg of ginkgo biloba extract, a recent study succeeded in reversing depression among elderly patients. Significant differences in mood, motivation, and memory were noted after only 4 weeks (Brown, 1996).
  Poor circulation to the extremities - Numerous studies have shown that 120 to 160mg of ginkgo biloba extract daily for 3 to 6 months is efficient in treatment of intermittent claudication (Brown, 1996). 

Safety
Ginkgo appears to be extremely safe and is well tolerated by most people. No major adverse effects or drug interactions were noted in 44 clinical trials involving 9772 participants, and side effects of any kind are rare (McCaleb et al, 2000). However, the following precautions should be taken when drug interaction is concerned:

• Drug interaction:
  • Patients who are on antidepressant drugs known as monoamine oxidase inhibitors (MAOI) are advised not to take ginkgo due to the theoretical possibility of negative effect (McCaleb et al, 2000; Brinker, 1998)
  • Ginkgo, taken together with anticoagulants such as aspirin, heparin and warfarin, can augment the anticoagulant effect, thus, altering clotting or bleeding times. Example of negative effects include excessive bleeding (Horowitz, 2000)Note: Information provided is based on thorough research done on scientific and reliable sources. However, it is not meant to substitute for the advice provided by your own physician or other medical professional. 

REFERENCES
1. Bratman, S., & Kroll, D. (1999). Natural Health Bible. Prima Health. USA.

2. Brinker, F. (1998). Herb Contradiction and Drug Interaction. Eclectic Medical Publications. USA.

3. Brown, D.J. (1996). Herbal Prescriptions for Better Health. Prima Health. USA.

4. Chevallier, A. (1996). The Encyclopedia of Medicinal Plants. Dorling Kindersley. UK.

5. Horowitz, S. (2000). Combining Supplements and Prescription Drugs – What Your Patients Should Know. Alternative & Complementary Therapies – August 2000, p. 177-183. USA.

6. McCaleb, R.S., Leigh, E., & Morien, K. (2000). The Encylopedia of Popular Herbs. Prima Health. USA.

7. Milam, L.J. (1999). Ginkgo Biloba.

8. Murray, M.T. (1995). The Healing Power of Herb. Prima Health. USA.