Dietary therapy uses food to treat and prevent diseases. Chinese medicine philosophy believes that a human being and his/her environment form an organic whole. Humans are integral parts of the environment. The environment provides air, water, and food for life. Therefore, things from the environment can keep the person healthy and treat diseases. Chinese medicine philosophy has a five-element theory to classify food into five categories. Foods within the same category have common features and are closed related. Foods have different categories have different tastes, flavors, and functional directions. Foods in different categories correspond to different internal organs. For example, salty foods for the kidney, bitter foods for the heart, sweet foods for the spleen, acrid foods for the lung, and sour foods for the liver. Moreover, dietary therapy uses the law of opposites. Cold foods treat hot diseases; hot foods treat cold diseases. Foods with lifting properties can be used to treat sinking, depressed, and hypofunctional conditions. Foods with sedating properties can be used to treat uprising, over-active, and hyperfunctional conditions.