According to Chinese tradition, old age is accompanied by a steady weakening of qi, the source of vitality. A large number of medicinal plants treat pathologies that appear from the age of 50 (circulatory, digestive, or memory problems). Those recommended below have a preventative action or are likely to treat some of these disorders. Other treatments applicable to diseases related to aging, such as arthritis, are discussed in the chapter devoted to bone and muscle problems. There are many plants that help keep fit. In China, ginseng is prescribed to the elderly during harsh winters. This excellent tonic improves vitality and strengthens resistance to stress and infectious diseases. It is recommended for convalescents or after prolonged stress. Eleutherococcus is both a tonic-like Ginseng, which it can replace-which slows down aging, and a fortifying agent indicated for convalescents.v