The Latest on Green Tea ~ Try it for weight loss, skin protection, and more
by Clare M. Hasler, PhD. MBA
Taste For Life Magazine ~ February 2006
For years you've heard about the medicinal benefits of green tea (Camellia
sinensis)-one of the most widely consumed beverages in the world. Green tea
contains biologically active compounds, known as catechins, that may reduce
chronic disease risk and enhance health. Green tea consumption has been linked
to lower cardiovascular risk, higher bone density, and calming effects in
stressful situations.
More recently, researchers have investigated green tea for weight-loss
benefits, and it's emerging as an important ingredient in skin health. Dozens of
in vitro, animal, and epidemiological studies conducted over the last few
decades suggest that consumption of green tea may show promising benefits for
certain types of cancer.
Go Green to Get Lean
The incidence of overweight and obesity is a serious public health crisis in
the U.S. and other developed countries. Current estimates show that
approximately 65% of U.S. adults are overweight (defined as a body mass index
[BMI] between 25 and 29.9) or obese (BMI of 30 or more). Obesity is a major
causative factor in a number of conditions including heart disease, diabetes,
hypertension, stroke, and even certain types of cancer. Clearly the most
successful weight-loss strategy is to reduce overall caloric intake, while
increasing caloric expenditure through exercise.
The 2005 United States Department of Agriculture (USDA) Dietary Guidelines
for Americans put forth strong recommendations on weight loss and physical
activity. "Making moderate physical activity a part of an adult's daily
routine for at least 30 minutes per day promotes fitness and reduces the risk of
chronic health conditions such as obesity, hypertension, diabetes, and coronary
artery disease," the guidelines state. They add: "Many adults need to
participate in up to 60 minutes of moderate to vigorous physical activity on
most days to prevent unhealthy weight gain, while adults who have previously
lost weight may need 60 to 90 minutes of moderate physical activity daily to
help avoid regain of weight."
With obesity reaching epidemic proportions in the U.S., it's not surprising
that significant research efforts are targeted toward this health concern, as
well as the role that various functional foods or other bioactive compounds may
play. The evidence is growing for green tea in this role. Ingredients that
stimulate the activity of the sympathetic nervous system, which, in turn,
suppresses hunger, enhances satiety, and stimulates energy expenditure, may
contribute to weight loss.
Bioactive components in green tea powder suppress fat accumulation in mice.
In humans, a green tea extract rich in epigallocatechin gallate (EGCG) increased
thermogenesis (production of heat in the body) and 24-hour energy expenditure.
Other researchers have hypothesized that an intervention that reduces the
positive energy balance by 100Kcal/day could offset weight gain in 90% of the
population.
In a recent placebo-controlled, double-blind clinical intervention trial, a
combination of capsaicin, green tea extract, tyrosine, and calcium increased
24-hour energy expenditure by about 2% per day, without raising heart rate or
having any other adverse effects. In a second study, 76 overweight and
moderately obese subjects followed a very low energy diet for four weeks,
followed by three months of weight maintenance. During the weight maintenance
period, the low-caffeine consumers who received a daily green tea-caffeine
mixture (270mg EGCG + 150mg caffeine) experienced reduced body weight, a lower
ratio of body fat, and increased resting energy expenditure. In a third
double-blind controlled study in which caffeine intake was minimized, daily
consumption of 690mg of green tea catechins for 12 weeks contributed to a
statistically significant reduction in body weight, BMI, waist circumference,
and body fat mass in 38 men. Researchers suggest that the catechin-mediated
thermogenic effect of tea has therapeutic potential for the management of
obesity.
Polyphenols for Photoprotection
Overexposure of the skin to ultraviolet (UV) rays results in a variety of
adverse effects, including premature aging, cataracts, and malignant skin
cancer. The incidence of melanoma in certain areas of this country increased by
400 percent between 1960 and 1986, making it the most common type of cancer with
one million cases diagnosed annually.
Clearly, the best protections against sunlight-related skin disorders are
avoiding sun exposure at times of peak intensity, the use of protective clothing
and conscientious application of sunscreens with a sun protection factor (SPF)
of 15 or higher. In addition, intensive research efforts continue to identify
plant extracts that may act as antiaging agents for the human skin, including
green tea.
Green tea catechins have been investigated for more than two decades for
their chemopreventive, natural healing, and antiaging effects in animal models.
Emerging data suggest that green tea components may benefit human skin, too. In
a small pilot study, application of diluted extracts of green tea applied to the
back for 30 minutes prior to exposure to solar-simulated UV radiation produced a
dose-dependent reduction in erythema, or redness of the skin. A 10% solution of
green tea polyphenols produced almost complete protection at 48 and 72 hours
after sun exposure. Application of green tea polyphenols also reduced the number
of sunburn cells, protected epidermal cells from UV-induced damage, and reduced
the DNA damage formed after UV radiation. More recently, in a
placebo-controlled,
double-blind study of 60 women aged 25 to 60, application of a gel containing 2%
EGCG twice a day for four weeks resulted in marked improvements in texture and
appearance of skin in 45% of subjects, with no reported side effects.
Natural Health Hut
