Disclosed is a water based method for extracting caffeine from alkaloid containing substances, in particular tea leaves. The method can be performed without the use of artificial substances. The method allows the other soluble, non-caffeine components of alkaloid containing substances to be part of the decaffeinated product, in particular, components such as catechins and antioxidants. Advantageously, the caffeine extracted from the alkaloid containing substances is reversibly adsorbed to an adsorbent and high percentile of the caffeine can be recovered from the adsorbent.