Green tea
All types of tea (green, black, and oolong) are produced from the
Camellia sinensis plant using different methods. Fresh leaves from the
Camellia sinensis plant are steamed to produce green tea.
Common names: Green tea, Chinese tea, Japanese tea
Latin name:
Camellia sinensis
What it is used for
- Green tea and green tea extracts, such as its component EGCG, have been used to prevent and treat a variety of cancers, including breast, stomach, and skin cancers.
- Green tea and green tea extracts have also been used for improving mental alertness, aiding in weight loss, lowering cholesterol levels, and protecting skin from sun damage.
How it is used
Green tea is usually brewed and drunk as a beverage. Green tea extracts can be taken in capsules and are sometimes used in skin products.
What the science says
Adults in Japan who consumed higher amounts of green tea had a lower risk of death due to all
causes and due to
cardiovascular disease, according to a study in the
September 13, 2006 issue of the
Journal of the American Medical Association. But
there was no link between green tea consumption and a reduced risk of death due to cancer.
These inverse associations of all-cause and cardiovascular death were
stronger among women, although the inverse association for
green tea consumption was observed in both sexes.
In women, for example, compared with those who consumed less than 1 cup per day of green tea,
those who consumed 5 or more cups per day had a 31 percent lower risk of CVD death. The study,
initiated in 1994, included 40,530 adults (age 40 to 79 years) in northeastern Japan, where green
tea is widely consumed.
The incidence of
prostate cancer, the most common cancer in American males,
is considerably lower in Asian countries than in the West. One reason advanced for this high
incidence is the high consumption of plant foods in Asia. A number of laboratory studies have shown
that green tea, one of the most widely used foods, has
anti-tumor effects. The Mayo Clinic report, in
the journal
Cancer Letters, identified a plant substance in green tea
that is a potent killer of prostate cancer cells. The researchers, led by Charles Y-F. Young,
Ph.D., tested four common components of green tea on three different prostate cancer cell cultures.
One of them, called EGCG, was found to be the most potent in inhibiting cell growth.
Researchers from Boston University Schools of Medicine and Public Health have shown that
compounds found in green tea may offer some protection from development of breast cancer. The
researchers, led by Gail Sonenshein, MD, a professor of biochemistry, and Adrianne Rogers, MD, a
professor of pathology at Boston University School of Medicine, compared
breast cancer development in the 2 groups of female rats.
They found that the rats given green tea developed their tumors later than rats drinking water and
also had a 70%
reduction in tumor weight compared to those receiving
water. The green tea group also had less invasive cancers than the water-fed group.
Side effects and cautions
- Green tea is safe for most adults when used in moderate amounts.
- Green tea and green tea extracts contain caffeine.
- Green tea contains small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective.
- Tell your health care providers about any herb or dietary supplement you are using, including green tea. This helps to ensure safe and coordinated care.