To understand food in Chinese Medicine, we first have to understand a little bit about how the ancient Chinese viewed the world they lived in.
An important concept is the idea of xiang sheng or mutual arising, where all things are seen to be related and connected to each other. This brought about the notion of Yin Yang, a commonly known symbol reflecting this idea which we see frequently now. This influenced the way in which foods are categorised according to their temperature. Yin foods are likely to be more cool in nature, such as bananas or fresh mint. Yang foods are likely to be more hot in nature such as black pepper or chilli.
Another way of classifying information was in the form of the wu xing or five phases. This observed common occurrences in the world and in a persons experience and was used to categorise those of a similar nature. The seasons, emotions, stages of life, colours, tastes, smells, personalities and so on were all seen to be reflections of each other. Foods were classified as sour such as lemon, bitter such as celery, sweet such as carrots, pungent such as mustard and salty such as seaweed. Each flavour is seen to have a different action upon the body. If consumed excessively or insufficiently then it can lead to disease. To understand this we can think about what happens if we eat too much sweet or salty food for a long period of time.
The theory of acupuncture and Chinese herbal medicine helped to develop an understanding of how foods we eat can have an effect on the systems of the body. One way we can experience this is the difference between some spicy foods, mustard for example can give a warm sensation in the nose, chilli we may feel in the throat or tongue, ginger we can feel deeper in the digestive system.