Ginkgo biloba
The star of herbal brain boosters is the extract of the leaves of the Ginkgo biloba tree, which is revered for its ability to improve memory, thinking, reasoning, and general mental alertness. Ginkgo increases blood circulation through the brain to boost the brain's energy and metabolism. It is an antioxidant and facilitates the transmission of nerve signals.
Ginkgo biloba has a long, colorful history. It is the oldest tree on Earth, with fossils showing it to be more than 200 million years old. In fact, it's the last survivor of an ancient family of trees. You can say that it is the "Ishi" of the trees. (Ishi was the last surviving member of his tribe.) About 2,000 years ago, the Ginkgo biloba was nearly extinct; Chinese monks saved it, because they considered it to be a sacred tree. After that, they grew ginkgo in their temples. The extract from the leaves was used as a brain tonic by Chinese herbalists. The name means "biloba." If you look at a ginkgo leaf, you'll see that its veins spread out in two directions, so that it looks as if the leaf is cut into two separate halves, like the lobes of the brain.
The ginkgo tree can now be found all over the world. It has won acceptance by physicians in Europe, where doctors write more than a million prescriptions a month to improve brain circulation.
Research into ginkgo's effects on humans shows that it speeds up the flow of blood and oxygen through the body and brain. It increases the manufacture of adenosine triphosphate (ATP), which is sometimes described as the "universal energy molecule." The theory is that ginkgo extract facilitates brain functioning by helping it to better metabolize glucose, which produces oxygen, the brain's main source of fuel and energy. Additionally, ginkgo keeps the brain arteries from clogging up with blood platelets, by keeping the arteries flexible so that the platelets don't collect together on the artery walls. It helps the nerve cells transmit signals from one to another. Ginkgo is a vasodilator, which means it dilates the blood vessels, especially tiny capillaries. This increased circulation helps protect the nerves from the damage that can result from a reduced supply of blood and oxygen, as often occurs with age. If all these benefits aren't enough, this astounding herb is hailed for its role as an antioxidant and its ability to improve circulation, which protects nerves from damage from reduced blood and oxygen supplies, and contributes to protection from the damage by free radicals.
The active components of ginkgo leaves are flavonoid molecules called ginkgo heterosides, several terpene molecules, and organic acids, including vitamin C. The Ginkgo biloba extract (GBE) prepared from the leaves is marketed in Europe as Tanakan, Rokan, and Tebonin. Culture, harvesting, and extraction processes are standardized and controlled, which makes treatment more reliable and research on its effects easier.
In The Healing Power of Herbs, Michael Murray reviews a substantial and impressive body of research that supports traditional folk wisdom about ginkgo's beneficial impact on short-term memory, mental alertness, and general brain functioning. He says that GBE promotes an increased rate of nerve transmission, improved synthesis and turnover of cerebral neurotransmitters, and promotion of acetylcholine receptors in the hippocampus.
GBE can help people just beginning to experience a decline in their cognitive functioning due to Alzheimer's disease or other symptoms of aging. Research has shown that in aged animals GBE can normalize acetylcholine receptors in the hippocampus and increase cholinergic transmission, which helps Alzheimer's victims. But Murray cautions that GBE can delay but not prevent onset of Alzheimer's. On the other hand, he says, GBE is usually effective in reversing decline when the mental deficit is due to vascular insufficiency or depression.
Ginkgo extract is usually administered in a concentrated powdered form or in a tincture. Murray reports that at least eight days are necessary before the first effects are manifested, and that most people notice benefits within two to three weeks, Pelton says that very high doses have improved short-term memory in as little as one hour. But, generally, it is a relatively slow-acting substance. Ginkgo products are available in most health-food stores. The typical regime involves taking it three times a day, since ginkgo has a half-life of about three hours, with most of the substance having dissipated after about six hours.
No side effects from the leaf extract have been reported in the scientific literature. The ginkgo fruit, on the other hand, probably should be avoided, because it causes severe allergic reactions similar to that of poison ivy and poison oak in most people who even touch it.

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