Between its metabolism-boosting powers and ability to prevent colds, green tea is a miracle in your mug. While there are several reasons to sip it each day , many wonder if one glass alone can provide you with the acclaimed benefits. Before you go to town guzzling, learn if it's possible to have too much of a good thing (the results may surprise you).
If you find yourself drinking a cup or two of green tea a day, you're doing things right! Dr. Zuo Feng Zhang , a cancer epidemiology researcher at UCLA, and the University of Maryland Medical Center  recommend two to three teacups (not mugs) a day, which will prove beneficial to your health.
However, drinking up to five cups a day  has been shown to decrease risk for stomach cancer. In fact, if you're trying to lose weight and to boost your metabolism, the best results have been seen with drinking seven cups a day  (this study, though, has not been tested directly on humans). Additionally, many other medical studies have shown that the more green tea consumed daily the greater the benefits, with 10 cups being the upper limit . If you are sensitive to caffeine, or suffer from insomnia, 10 cups of green tea is probably going to be too much for your system, regardless of the benefits.
There are a few negative consequences to drinking lots and lots of green tea. The tannins found in both green and black tea can decrease absorption of folic acid , an important vitamin that helps decrease birth defects. If you are pregnant or trying to get pregnant, you should definitely limit your green tea consumption to two cups a day, or skip it altogether. Green tea can also interfere with the absorption of iron, too, so it's recommended that you avoid drinking green tea with meals and just drink it between them.
How many cups of green tea do you drink a day?
— Additional reporting by Emily Bibb