Drinking three or more cups of tea a day is as good for you as drinking plenty of water and may even have extra health benefits.  Tea not only rehydrates as well as water does, but it can also protect against heart disease and some cancers. The flavonoids are believed to be the key ingredient in tea that promote health.  These polyphenol antioxidants are found in many foods and plants, including tea leaves, and have been shown to help prevent cell damage.