The U.S. Food and Drug Administration (FDA) has rejected claims
of health benefits for green tea. [4]
"There is no credible scientific evidence that drinking green tea
reduces the risk of heart disease".
"FDA concludes there is no credible evidence to support qualified
health claims for green tea or green tea extract and a reduction of
a number of risk factors associated with CVD" (cardiovascular
disease).
The FDA has said that green tea likely does not reduce breast,
prostate or any other type of cancer risk.
[The text below describes studies which show an association between
drinking tea and better health, but they do not demonstrate that
drinking tea causes better health. It may just be that healthy
people like tea.]
Contradicting the FDA, a 2006 study published in the September 13
issue of the Journal of the American Medical Association shows that
adults who consumed three or more cups of green tea per day had a
lower risk of death due to cardiovascular disease. The study,
conducted by the Tohoku University School of Public Policy in
Japan, followed 40,530 Japanese adults, ages 40 to 79 years, with
no history of stroke, coronary heart disease or cancer at baseline
beginning in 1994. The study followed all participants for up to 11
years for death from all causes and for up to 7 years for death
from a specific cause. Participants who consumed 5 or more cups of
tea per day had a 16 percent lower risk of all-cause mortality and
a 26 percent lower risk of cardiovascular disease than participants
who consumed less than 1 cup of tea per day. The study also states,
"If green tea does protect humans against CVD or cancer, it is
expected that consumption of this beverage would substantially
contribute to the prolonging of life expectancy, given that CVD and
cancer are the two leading causes of death worldwide."
A 2006 study published in The American Journal of Clinical
Nutrition (Vol. 83, pp 355-361) showed that elderly Japanese people
who drank more than 2 cups of green tea a day had a 50 percent
lower chance of having cognitive impairment than those who drank
less or who consumed other tested beverages. [5] The high amount of
catechins found in green tea[6] is thought to be the reason.
In May 2006, researchers at Yale University School of Medicine
weighed in on the issue[7] with a review article that looked at
more than 100 studies on the health benefits of green tea. They
pointed to what they called an "Asian paradox," which refers to
lower rates of heart disease and cancer in Asia despite high rates
of cigarette smoking. They theorized that the 1.2 liters of green
tea that is consumed by many Asians each day provides high levels
of polyphenols and other antioxidants. These compounds may work in
several ways to improve cardiovascular health, including preventing
blood platelets from sticking together and improving cholesterol
levels, said the researchers, whose study appeared in the May issue
of the Journal of the American College of Surgeons. Specifically,
green tea may prevent the oxidation of LDL cholesterol (the "bad"
type), which, in turn, can reduce the buildup of plaque in
arteries, the researchers wrote.
Green tea has also been claimed to reduce stress and produce alpha
waves. This is thought to be due to high antioxidant levels and the
presence of l-theanine, which is a glutamate analog present in
green tea that can cross the blood-brain barrier and reduce
glutamate excitotoxicity during stress and ischemia.
source from
http://en.wikipedia.org/wiki/Green_tea
