reen tea is more than just hot, flavored water.The bioactive substances in the tea leaves dissolve in the water and make it into the final drink.When you drink a cup of quality tea, you’re actually getting a large amount of beneficial substances with potent biological effects (1).The best known of these is caffeine. A cup of green tea contains much less caffeine (24-40 mg) than a cup of coffee (100-200 mg), but still enough to have a mild effect.Caffeine is a well known stimulant that has been shown to aid fat burning and improve exercise performance in numerous studies (2, 3).