Public interest in various aspects of oriental medicine including acupuncture, massage, macrobiotics, and herbal medicine has grown steadily in the Western world. The concepts of oriental medicine have their basis in Daoism, a school of thought that dates back to prehistoric times.
Daoists claim that there is a constant movement between two poles, the "yin" and the "yang", and that energy (vibration) between these two opposing poles is the activating force of all biological phenomena. They maintain that this constant flux, or movement, is easily observable in all living things-from a small molecule in a human being to a large planet. Yin can be defined as the tendency towards expansion and yang the tendency towards contraction (examples of yin are negative, female, passive, earth, moon; examples of yang are positive, male, active, sky, sun, splendid, warm). In essence, yin and yang are complementary forces which ideally must balance to create health and well being, or to establish correct or optimal conditions in the universe. The dynamic energy in all things, essentially the vehicle through which yin and yang operate, is called "ki" in Japan, "ch'i" in China, and "prana" in India. Every living thing has ki, but this energy and the quality of that energy differs from one living thing to another. In simple terms, the food and drink we consume every day give us ki, and the goal of oriental medicine is to regulate the intake of food and drink so as to maximise the harmonious flow of ki in the body. Proponents of the art of oriental medicine divide the body into a yin organ (for example, a hollow organ of absorption: gallbladder, small intestine) and a yang organ (dense, blood-filled organ of regulation: heart, liver, kidneys). The level of ki required by a yin or yang organ depends on its density and structure.