According to de Mejia, all teas provide some level of cancer protection because of their potent antioxidant activity, although green tea has more antioxidants than black tea.
She says that if you drink tea, within an hour, some antioxidant or cancer-fighting capacity will be circulating in your blood. We need to keep taking in antioxidants to compensate for the carcinogens we're exposed to in the environment.
She recommends drinking between 3 and 10 cups of green tea a day for antioxidant activity and consequent cancer protection. Three cups of tea provides more antioxidant activity than a serving of broccoli.
Admittedly, that's a lot of tea, but if you drink it instead of the water you should be drinking, you will notice other benefits as well.