To achieve the first, it is necessary to use food from without. Foods have been divided in Chinese medicine into "cool" and "hot" types.
為求得人體內部系統的和諧，就須借助外來食物，因此將食物分成涼性和熱性，火氣大就吃退火的涼性食品；體冷則補熱食，這也正是中醫所說的「食療同源」。