Green tea, as well as other types of tea, comes from the Camellia sinensis plant. The difference between green tea and other tea types lies in the method used to process the leaves; green tea is a result of steaming.
Green tea has a series of health benefits and is growing to be a widely popular drink in the West. But what does scientific research reveal, and are there side effects in drinking or taking green tea?
Find out what the National Center for Complementary and Alternative Medicine (NCCAM) has to say.
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 supports 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. The problems do 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 discontinue use and consult a health 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 all your health care providers about any complementary health practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.
Source: NCCAM
