Green tea, native to China and India, has been consumed and hailed for its health benefits for centuries globally, but has only recently gained popularity in the US.
Tea is considered the most consumed beverage in the world behind water, however 78% of the tea consumed worldwide is black and only about 20% is green.
All types of tea except herbal tea are brewed from the dried leaves of theCamellia sinensis bush. The level of oxidation of the leaves determines the type of tea.
Green tea is made from un-oxidized leaves and is one of the less processed types of tea (with white tea the least) and therefore contains one of the most antioxidants and beneficial polyphenols.
Green tea was used in traditional Chinese and Indian medicine to control bleeding and heal wounds, aid digestion, improve heart and mental health and regulate body temperature.4 Recent studies have shown green tea can potentially have positive effects on everything from weight loss to liver disorders, type 2 diabetes and alzheimer’s disease.
How does Green tea works?
The useful parts of green tea are the leaf bud, leaf, and stem. Green tea is not fermented and is produced by steaming fresh leaves at high temperatures. During this process, it is able to maintain important molecules called polyphenols, which seem to be responsible for many of the benefits of green tea.
Polyphenols might be able to prevent inflammation and swelling, protect cartilage between the bones, and lessen joint degeneration. They also seem to be able to fight human papilloma virus (HPV) infections and reduce the growth of abnormal cells in the cervix (cervical dysplasia). Research cannot yet explain how this works.
Green tea contains 2% to 4% caffeine, which affects thinking and alertness, increases urine output, and may improve the function of brain messengers important in Parkinson’s disease. Caffeine is thought to stimulate the nervous system, heart, and muscles by increasing the release of certain chemicals in the brain called “neurotransmitters.”
Antioxidants and other substances in green tea might help protect the heart and blood vessels.
Side Effects of Green Tea
Green tea is LIKELY SAFE for most adults when consumed in moderate amounts. Green tea extract is POSSIBLY SAFE for most people when taken by mouth or applied to the skin for a short time. In some people, green tea can cause stomach upset and constipation. Green tea extracts have been reported to cause liver problems in rare cases.
Special Precautions & Warnings
Pregnancy and breast-feeding: If you are pregnant or breast-feeding, green tea in small amounts about 2 cups per day is POSSIBLY SAFE. This amount of green tea provides about 200 mg of caffeine. However, drinking more than 2 cups of green tea per day is POSSIBLY UNSAFE. Consuming more than 2 cups of green tea daily has been linked to an increased risk of miscarriage and other negative effects. Also, caffeine passes into breast milk and can affect a nursing infant. Don’t drink an excessive amount of green tea if you are pregnant or breast-feeding.
“Tired blood” (anemia): Drinking green tea may make anemia worse.
Anxiety disorders: The caffeine in green tea might make anxiety worse.
Bleeding disorders: Caffeine in green tea might increase the risk of bleeding. Don’t drink green tea if you have a bleeding disorder.
Heart conditions: Caffeine in green tea might cause irregular heartbeat.
Diabetes: Caffeine in green tea might affect blood sugar control. If you drink green tea and have diabetes, monitor your blood sugar carefully.
Diarrhea. Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea.
Irritable bowel syndrome (IBS): Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.
Glaucoma: Drinking green tea increases pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.
High blood pressure: The caffeine in green tea might increase blood pressure in people with high blood pressure. However, this does not seem to occur in people who regularly drink green tea or other products that contain caffeine.
Liver disease: Green tea extract supplements have been linked to several cases of liver damage. Green tea extracts might make liver disease worse.
Weak bones (osteoporosis): Drinking green tea can increase the amount of calcium that is flushed out in the urine. Caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of green tea). It is possible to make up for some calcium loss caused by caffeine by taking calcium supplements.