Green tea contains an abundance of phytochemicals, such as catechins, which are tannin derivatives that provide astringency to the drink. The amount of catechins in green tea varies depending on the time of the year, with larger amounts being found in crops grown later in the season. Also, younger leaves contain greater amounts of the phytochemicals than those that are more mature and can be used, therefore, to produce a more astringent tea. The greater the astringency of the tea, the more likely it is to be advantageous to one’s health because mounting evidence suggests that catechins fight cancer and exhibit both antiviral and antioxidant characteristics. Some research also indicates that the phytochemicals may function physiologically to regulate blood sugar, cholesterol, and blood pressure, as well.