Traditional Vietnamese medical theory

The beliefs of Vietnamese folk medicine associate illness with the absence of any of the three souls which maintain life, intelligence, and the senses or of the seven spirits which collectively sustain the living body. A number of rituals performed at childbirth, which are aimed at protecting the mother and the infant from medical and magical dangers, derive from these beliefs but they play a relatively limited role in medical behaviour generally. Conversely, Chinese medicine plays a major role in the maintenance and restoration of health and is observed by Vietnamese. Principles from Chinese medicine provide the scripting for the management of birth for both groups and more generally, establish guidelines whereby good health may be maintained.

According to Sino-Vietnamese medical theory, the body has two vital and opposite life forces which capture the essence of yin (breath) and yang (blood) in accordance with the ‘five evolutive phases’ (wood, fire, earth, metal, and water). The proper circulation and balance of the yin and yang ensure the healthy circulation of blood and thus good health; disequilibrium and disharmony cause ill health, illness, physical and mental, can be identified by the imbalance or excess of yin over yang or yang over yin. Foods and medicine, also classified according to their reputed intrinsic nature as yin (cold) and yang (hot), may be taken therapeutically to correct the imbalance resulting from ill health or to correct imbalance due to the overindulgence in a food manifestly excessively ‘hot’ or ‘cold’ or due to age or changed physiological status, for example pregnancy.

Foodstuffs may also be identified as tonic or antitonic, toxic or poison, or as having wind. A further small group of foods are ascribed magical properties. Other foods may be classified as neutral or remain outside any classification system and hence have no overt therapeutic use.
While the classification of foods as hot, cold, tonic, poison, windy, and neutral is based on the intrinsic nature of the foods, in practice they are identified predominantly according to their physical effects on the body. Ultimately, the system is both individual and arbitrary, and there appears no firm correlation to the raw and cooked states of the food, the method of cooking, the spiciness, or the calorific value of the food.

In general, leafy vegetables and most fruit are classified as cold and are said to cool the body; meat, condiments, alcohol, and fatty foods are classified as hot and are said to heat the body. Tonic foods, believed to increase the volume of blood and to promote health and energy, include ‘protein-rich’ foods, high fat, sugar, and carbohydrate foods (fired food, sweet fruit, honey, and rice) and medicines (alcohol and vitamins). Sour foods, and sometimes raw and cold foods tend to be considered antitonic and are believed to deplete the volume of blood. ‘Wind’ foods include raw foods, leafy vegetables, and fruit and often are classified as cold; they reputedly cause wind illness such as rheumatism and arthritis. Beef, mutton, fowl, fish, glutinous rice, and bananas are considered potentially toxic and may cause convulsions, skin irritation, and infection.