For as long as 5,000 years, people have consumed tea leaves steeped in boiling water. But tea—and green tea, especially—is much more than just a beverage: Studies suggest that it may aid in weight loss, reduce cholesterol levels, and even help treat or prevent cancer. Once available only as a drink, green tea is now available as an extract in capsule form and is an ingredient in weight-loss and energy supplements, and even topical beauty treatments.

Green tea is made from the same plant, Camellia sinensis, as white, black, and oolong teas. The difference is in the processing: Green and white teas are made from unfermented leaves and contain the highest concentrations of polyphenols, a type of antioxidant. (Herbal and rooibos teas aren’t really teas at all, but are made from different mixtures of plants.) One of the most powerful antioxidants in green tea is called epigallocatechin gallate, or EGCG. Tea also contains caffeine (although white and green teas have two to three times less than black, and all teas have significantly less caffeine than an equal serving of coffee), which contributes to its ability to improve alertness.

Traditionally valued in China and India for its properties as a stimulant and diuretic, modern medicine has shown that green tea can also boost mental processing. Research also suggests that it can slow the growth of some cancers and benign skin tumors; increase metabolism and help burn fat; and reduce inflammation associated with arthritis, Crohn’s disease, and ulcerative colitis.

Most research has studied the impact of 1 to 10 cups of green tea a day, and the beverage is safe for most adults when used in these quantities. However, people taking blood-thinning medications may find that the vitamin K in green tea makes their treatments less effective. For those taking concentrated doses of green tea in capsule form, a few cases of liver problems have also been reported.

ADDITIONAL FACTS

  1. It is suspected (but not proven) that green tea and EGCG may help protect against sun damage, so they are now popular ingredients in sunscreens and other skin-care products.
  2. Early research using a green tea combination product was thought to have shown some success in helping women conceive, although more research on green tea alone needs to be done.
  3. When sold as a beverage, green tea is often classified by the region in which it was grown. The most expensive varieties from southwest China can cost up to $150 a pound.