In the Chinese medical-dietary system, the green bean of coffee would be classified as an herb that regulates liver qi, which is its therapeutic route to strong energy stimulation (attributed chemically to caffeine's action on the nervous system). The green bean is of the color of the wood element (associated with liver); more important to classification, however, is the concept that when the liver qi is constrained, the entire body energy becomes depressed. By vigorously dredging the stagnated liver qi, a strong sense of mental and physical vitality is experienced. The early use of coffee beans to regulate menstruation is consistent with the Chinese medical approach of regulating menstruation by dredging stagnant liver qi. The green coffee bean also cools the constrained liver qi. When the bean is roasted, it retains its basic medicinal properties, but transforms from a cooling herb to a warming herb. Roasting herbs is a common processing method used in China.