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We hear a lot of exciting
health information. Research is ongoing and not conclusive yet. More
clinical studies are needed in order to understand the role of
antioxidants effects on us and tea.
The following studies are
provided for your information, since it has become hard to ignore the
ongoing scientific studies and positive publicity that tea is receiving
over the exciting potential health benefits.
Learn more about the health
benefits of both green and black tea by clicking on the study of
interest to read the full article.
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September 24, 2002
Tea Council of Canada
NEW STUDY PROVIDES EVIDENCE
THAT TEA CONSUMPTION REDUCES
LOW DENSITY LIPOPROTEIN ("BAD" CHOLESTEROL) LEVELS
Additional New
Findings Strengthen Link Between Tea and
Decreased Risk of Certain Types of Cancer
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WASHINGTON, DC, September
24, 2002 - Leading scientists from around the globe convened yesterday in
Washington, DC for the Third International Scientific Symposium on Tea &
Human Health: Role of Flavonoids in the Diet to review the latest findings
on the potential health benefits of tea, including new studies on promoting
heart health and reducing the risk for cancer.
The
latest data provide further evidence of tea's potential disease-fighting
capabilities. Major research developments since the Second Symposium on Tea
& Human Health, held in 1998, include new results that suggest:
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Tea may reduce Low Density
Lipoprotein (LDL, or "bad" cholesterol) levels by 10 percent
Consumption of as little
as four cups of tea per day may contribute to cardiovascular health by
improving endothelial function, as seen in clinical studies
Tea may reduce oxidative
stress, as indicated by decreases in DNA damage in smokers
Tea consumption is linked
with a 60 percent decrease in rectal cancer among women
The symposium,
which was sponsored by the
American Cancer Society,
the American College of Nutrition, the American Health Foundation, the
American Society for Nutritional Sciences, the Food and Agriculture
Organization, the Linus Pauling Institute and the Tea Council of the
U.S.A., was held at the United States
Department of Agriculture (USDA). Leading researchers from around the world
joined American scientists in presenting the latest clinical, laboratory and
epidemiological data on the role of tea in promoting healthfulness and
reducing the risk of disease.
"As investigators continue to study the multiple effects that tea has on
human health, more research supports tea's potential in helping to reduce
the incidence of major diseases," said the meeting's co-chair, Jeffrey
Blumberg, PhD, Professor, Friedman School of Nutrition Science and Policy at
Tufts University, and Chief, Antioxidants Research Laboratory, Jean Mayer
USDA Human Nutrition Research Center on
Aging at
Tufts University, Boston. "The scientific
community is making tremendous strides in discovering the potential for
flavonoids in black and green tea and other plant foods to promote health
and reduce the risk of certain chronic diseases, findings which could have
significant implications for public health."
Studies Suggest Tea Consumption May Lower "Bad" Cholesterol.
The results of a new clinical study suggest that tea consumption may
decrease LDL cholesterol by 10 percent when combined with a "Step I" type
diet, moderately low in fat and cholesterol, as described by the American
Heart Association and the National Cholesterol Education Program. The study,
conducted at the USDA Beltsville Human Nutrition Research Center in
Beltsville, MD, is the first investigation of tea in which the subjects'
diets were precisely controlled by having them eat meals prepared at the
research facility.
In addition to the "Step I" diet, all subjects consumed five cups of either
caffeinated tea, a placebo beverage with color and flavor closely matching
that of the tea, but having no caffeine, or a similar placebo beverage with
caffeine added to the same concentration as in the tea. "This clinical trial
is one of the first to show significant benefits of tea on blood
cholesterol," said Joseph Judd, PhD, Acting Director, Beltsville Human
Nutrition Research Center, and the study's lead researcher. "The controlled
diet allowed us to closely examine the effects of tea drinking in
conjunction with a healthy diet on cholesterol levels free from the
interference by variation in other nutrients or components of the diet."
These new developments in tea research add to the growing body of evidence
suggesting that tea consumption positively impacts cardiovascular health in
several different ways, with as little as two to four cups per day. Another
study, published in the May 6, 2002 issue of Circulation: Journal of the
American Heart Association, found that study participants who drank four
cups of tea per day had a significantly lower risk of death following a
heart attack. Additional research suggests that tea flavonoids may support
endothelial function, an important indicator of cardiovascular health. More
research is necessary to conclude that tea may be used as a preventive
measure to combat the risk of heart disease, but the results so far are
extremely promising.
New Developments in Cancer
Research
Lung Cancer
In the first intervention study using tea, preliminary findings suggest that
smokers who drank tea had significantly lower levels of oxidative DNA
damage. Oxidative stress to DNA is implicated in a multitude of chronic
diseases, including cancer. In this clinical study, smokers drank four cups
of decaffeinated green tea, decaffeinated black tea or water for four
months. Researchers then looked at several biomarkers of oxidative stress,
or DNA damage. Preliminary results found that smokers who drank
green tea showed a significant decrease in urinary biomarkers of oxidative
DNA damage. Researchers have also observed similar results in animal
studies, in which tea inhibited tobacco-induced lung tumor formation. "We
know that smokers' bodies sustain a high level oxidative damage and are at
risk for certain cancers," said Iman Hakim, MD, PhD, MPH, Division Director,
Health Promotional Sciences, Arizona Cancer Center and Research Associate
Professor of Public Health, College of Public Health, University of Arizona.
"Because this population has elevated levels of oxidative damage at
baseline, we are better able to observe the effects that tea consumption has
on oxidative stress."
Rectal Cancer
According to an epidemiological study conducted in Russia to
determine the protective nature of black tea against rectal cancer, women
who consume high levels of tea were shown to have a 60 percent reduction in
the risk of rectal cancer, as compared to women who drank relatively low
amounts of tea. Researchers identified patients recently diagnosed with
rectal cancer and questioned them about their tea-drinking habits, then
divided the participants into three groups based on the amount of dry tea
used per month: low consumption, less than 80g dry tea per month; moderate
consumption, 80 - 160g dry tea per month; and high consumption, more than
160g dry tea per month. The Russian population was selected, not only
because tea drinking is an essential part of the culture, but also because
of the traditional method in which tea is prepared.
As is the custom, black tea is brewed at a high concentration, then consumed
in a diluted form throughout the day. Instead of measuring tea consumption
in terms of fluid measures, intake was measured by the amount of dry tea
used to make the tea concentrate. In addition to the 60 percent reduction in
risk of rectal cancer found in heavy tea-drinking women, researchers found
that women who were moderate tea-drinkers had a 52 percent reduction in the
risk of rectal cancer as compared to women in the low consumption group.
Although men were also recruited for the study, the findings were much
weaker, possibly due to the men's high volume of alcohol intake.
These new findings are an important step in determining the potential role
of tea components in cancer prevention and complements previous studies that
have found tea drinking to be associated with a decreased risk of certain
cancers. More research is necessary before a definitive link can be made,
but the current research looks promising.
Mechanism of Action and
Bioavailability of
Tea Flavonoids
While the established body of tea research strongly suggests that tea
consumption offers a wide variety of health benefits, ranging from the
promotion of heart health and reduced risk of some forms of cancer, the
actual mechanisms by which the benefits are wrought remains under
investigation. In vitro studies suggest that tea flavonoids protect against
oxidation, but there may be other mechanisms by which tea components
function once they are absorbed into the body.
During digestion, flavonoid molecules undergo biochemical changes. Since
these compounds are modified in the gut, flavonoids may still protect
against oxidative stress, but may function by other mechanisms as well in
vivo. In vivo studies suggest that flavonoids interrupt the pathway of
oxidative stress and intercept the "message" for apoptosis, or cell death.
Black tea's flavonoids are complex in structure and appear to be absorbed at
different points in the body. Some of the larger molecules are not absorbed
in the stomach or small intestines, but remain intact until they reach the
colon, where they are partly absorbed into the bloodstream. The remaining
flavonoids may act as antioxidants and reduce the risk of colon cancer.
Because black tea's flavonoids remain intact through much of the
gastrointestinal tract, it seems that the flavonoids may have potential
benefits at various points throughout the gut.
Conversely, the principle constituents of green tea, are simple flavonoids,
called catechins, which are quickly absorbed into the body after
consumption. "Because green and black tea flavonoids appear to be absorbed
and metabolized at different points throughout the digestion process,
flavonoids may have an even wider range of protective benefits to various
body systems than originally thought," explained Dr. Blumberg.
Looking Toward the Future
The ongoing scientific exploration of the health benefits of drinking tea
has led to a growing body of research that points to tea as being an
important contributor to overall health. Research continues to show that
flavonoids seem to have a potent effect in maintaining the health and
function of cells and physiological systems - and tea is a major source of
flavonoids in the human diet.
"The research presented at this year's symposium further extends the
scientific evidence that tea may have a favorable effect on the
cardiovascular system and may positively impact health in many other ways,
including reducing the risk for some cancers," said Dr. Blumberg.
Looking towards the future, researchers plan to probe deeper into the
various mechanisms by which tea flavonoids function in the body and the
implications these mechanisms have on human health and disease prevention.
Clinical trials now underway and being planned will provide further
important information about the role of tea in health promotion.
Supporting Research
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Tea and Cancer:
Epidemiology and Clinical Studies
by Dr. Iman Hakim
Tea and Blood
Lipids by
Dr. Joseph T. Judd
Cardiovascular Effects of Tea
by
Dr. Joseph Vita
For more information
please contact:
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Tea Council of Canada
(416) 510-8647
info@tea.ca |
Barbara King/Robin
Foroutan
Aronow & Pollock Communications, Inc.
212-941-1414
bking@aronowandpollock.com
rforoutan@aronowandpollock.com |
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