Green Tea

How does Green Tea work?

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. It also contains antioxidants and other substances that might help protect the heart and blood vessels.

Are there safety concerns?

Green tea is safe for most adults. Green tea extract seems to be safe for most people for short-term use. In some people, green tea can cause stomach upset and constipation. Green tea extracts have been reported to cause liver problems.

Too much green tea, such as more than five cups per day, can cause side effects because of the caffeine. These side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Green tea seems to reduce the absorption of iron from food.

If you are pregnant or breastfeeding, green tea in small amounts is probably not harmful. Do not drink more than 2 cups a day of green tea. This amount of tea provides about 200 mg of caffeine. Consuming more than this amount has been linked to an increased risk of miscarriage and other negative effects.

Caffeine is probably safe in children in amounts commonly found in foods.

Avoid consuming large amounts of green tea if:
  • You are pregnant or breast-feeding.
  • You have a heart condition.
  • You have a liver disease.
  • You have severe anemia.
  • You have high blood pressure. Small amounts of green tea taken regularly do not seem to raise blood pressure, but blood pressure can be affected in someone who isn't used to the caffeine in green tea.
  • You have glaucoma.
  • You have anxiety disorder.

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Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


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