Possible side effects from drinking too much green tea include insomnia and a reduction in iron absorption. Otherwise, health benefits typically improve with increased consumption, even in individuals drinking up to 10 cups per day.
Studies show that drinking up to 5 cups of green tea per day sometimes reduces the risk of stomach cancer. Drinking up to 7 cups per day often boosts metabolism and aids weight loss.
Pregnant women or women trying to become pregnant should limit themselves to 2 cups per day, as excess green tea reduces the absorption of folic acid. Folic acid aids in the prevention of birth defects.