Health Benefits
A 2006 study published in the September 13 issue of the Journal of
the American Medical Association concluded "Green tea consumption is
associated with reduced mortality due to all causes and due to
cardiovascular disease but not with reduced mortality due to cancer."
The study, conducted by the Tohoku University School of Public Policy
in Japan, followed 40,530 Japanese adults, ages 40-79, 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 one
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 study published in the February 2006 edition of the American
Journal of Clinical Nutrition concluded "A higher consumption of green
tea is associated with a lower prevalence of cognitive impairment in
humans."
In May 2006, researchers at the Yale School of Medicine weighed
in on the issue 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.
A study published in the August 22, 2006 edition of Biological
Psychology looked at the modification of the stress response via
L-Theanine, a chemical found in green tea. It "suggested that the oral
intake of L-Theanine could cause anti-stress effects via the inhibition
of cortical neuron excitation."
In a double-blind, randomized, placebo-controlled trial done by
Division of Cardiovascular Medicine, Vanderbilt University Medical
Center, Nashville, Tennessee, 240 adults were given either
theaflavin-enriched green tea extract in form of 375mg capsule daily or
a placebo. After 12 weeks, patients in the tea extract group had
significantly less low-density lipoprotein cholesterol (LDL-C) and
total cholesterol (16.4% and 11.3% lower than baseline, p<0.01) than
the placebo group. The author concluded that theaflavin-enriched green
tea extract can be used together with other dietary approaches to
reduce LDL-C.
A study published in the January, 2005 edition of the American
Journal of Clinical Nutrition concluded "Daily consumption of tea
containing 690 mg catechins for 12 wk reduced body fat, which suggests
that the ingestion of catechins might be useful in the prevention and
improvement of lifestyle-related diseases, mainly obesity."
Antioxidants in green tea may prevent and reduce the severity of
rheumatoid arthritis, according to a CWRU's School of Medicine study
published in the April 13 2005 issue of the Proceedings of the National
Academy of Sciences. The study examined the effects of green tea
polyphenols on collagen-induced arthritis in mice, which is similar to
rheumatoid arthritis in humans. In each of three different study
groups, the mice given the green tea polyphenols were significantly
less likely to develop arthritis. Of the 18 mice that received the
green tea, only eight (44 percent) developed arthritis. Among the 18
mice that did not receive the green tea, all but one (94 percent)
developed arthritis. In addition, researchers noted that the eight
arthritic mice that received the green tea polyphenols developed less
severe forms of arthritis.
A German study found that an extract of green tea and hot water
(filtered), applied externally to the skin for 10 minutes, three times
a day could help people with skin damaged from radiation therapy (after
16-22 days).
A study published in the December 1999 American Journal of
Clinical Nutrition found that "Green tea has thermogenic properties and
promotes fat oxidation beyond that explained by its caffeine content
per se. The green tea extract may play a role in the control of body
composition via sympathetic activation of thermogenesis, fat oxidation,
or both."
In lab tests, EGCG, found in green tea, was found to prevent HIV
from attacking T-Cells. However, it is not known if this has any effect
on humans yet.
A study in the August, 2003 issue of a new potential application
of Cellular and Molecular Life Sciences found that "a new potential
application of (–)-epigallocatechin-3-gallate [a component of green
tea] in prevention or treatment of inflammatory processes is suggested"
