Green Tea
Keywords: Chinese tea, Japanese tea, cancer, mental
alertness
 © Steven Foster
Introduction
This fact sheet provides basic information about green
tea—common names, uses, potential side effects, and
resources for more information. 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 Names—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
- Laboratory studies suggest that green tea may help
protect against or slow the growth of certain cancers, but
studies in people have shown mixed results.
- Some evidence suggests that the use of green tea
preparations improves mental alertness, most likely because
of its caffeine content. There are not enough reliable data
to determine whether green tea can aid in weight loss,
lower blood cholesterol levels, or protect the skin from
sun damage.
- NCCAM is supporting studies to learn more about the
components in green tea and their effects on conditions
such as cancer,
diabetes, and heart disease.
Side Effects and
Cautions
- Green tea is safe for most adults when used in moderate
amounts.
- There have been some case reports of liver problems in
people taking concentrated green tea extracts. This problem
does not seem to be connected with green tea infusions or
beverages. Although these cases are very rare and the
evidence is not definitive, experts suggest that
concentrated green tea extracts be taken with food, and
that people should discontinue use and consult a heath care
practitioner if they have a liver disorder or develop
symptoms of liver trouble, such as abdominal pain, dark
urine, or jaundice.
- Green tea and green tea extracts contain caffeine.
Caffeine can cause insomnia, anxiety, irritability, upset
stomach, nausea, diarrhea, or frequent urination in some
people.
- 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 complementary
and alternative practices you use. Give them a full picture
of what you do to manage your health. This will help ensure
coordinated and safe care.
Sources
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