General Description
Ginkgo biloba (also known as the maidenhair tree) is a deciduous
tree native to China and cultivated widely throughout the southern
and eastern United States. It may live up to 1,000 years, growing
up to 120 feet in height and 4 feet in diameter. Its short, horizontal
branches bear fan-shaped leaves measuring 5 to 10 centimeters in
width. The tree bears an inedible, berry-like fruit with small edible
seeds. Extracts from ginkgo leaves are used for health purposes.
Health applications
History and traditional use
The durable ginkgo biloba tree is often called "the living fossil"
because it is the world's oldest living tree species, with fossil
records going back more than 200 million years. Destroyed during
the last ice age in all regions of the earth but China, ginkgo once
grew widely across North America and Europe. It was reintroduced
to America in 1784. Ginkgo's history as a therapeutic herb can be
traced back almost 5,000 years. Chinese medical texts from as far
back as 2800 B.C. document the use of ginkgo leaves as a brain tonic
and for relief of asthma and coughs.
Chemical compostition
The active components in ginkgo leaves include antioxidant compounds
known as ginkgo flavone glycosides, and unique terpene lactone
compounds called ginkgolides and bilobalides. Ginkgo biloba extracts
are commonly standardized to concentrations of 24% flavone glycosides
and 6% terpene lactones, and this concentration is used in most
medical studies.
Ginkgo and circulation
Antioxidant compounds in ginkgo biloba extract help promote circulation
by inhibiting platelet aggregation (the clumping together of blood
cells).1 Ginkgo extract can be helpful for
improving blood flow to the extremities, with studies showing
significant improvements in patients suffering from peripheral
arterial disease.2-4 Ginkgo's ability to enhance
blood flow may also make it useful for men suffering from impotence
caused by reduced blood flow.5,6
Memory and Alzheimer's
Because it enhances blood flow to the brain, many people take
ginkgo biloba to improve their memory. Studies have shown that
ginkgo may stabilize and, in some cases, even improve mental function
in patients with Alzheimer's
and other forms of dementia.7-9 Another study
indicates that ginkgo extract may help boost working memory in
healthy subjects as well.10
Dosage/Toxicity
Most people take divided doses, totaling 120 to 160 mg per day,
of an extract standardized to 24% flavone glycoside and 6% terpene
lactone concentration. Clinical studies have used doses ranging
from 40 to 300 mg per day.4-10 Ginkgo is safe
and generally well tolerated, with a very low occurrence of side
effects. Stomach discomfort, headaches, and dizziness have been
reported by a small percentage of users.11
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