The ancient Chinese philosophy of yin 阴 and yang 阳 – often shortened to yin yang – is a concept used to describe how apparently opposite forces are in actuality complementary to each other. The theory suggests that these complementary forces are present in all things, and that it is necessary for these forces to be balanced. This differs from Western society, where people predominantly believe in good versus evil, and that these forces are resolutely and unequivocally opposed to one another with no way of connecting the two.

Yin and yang are represented by many tangible dualities, such as light and dark, fire and water, and male and female. It is believed that everything has both yin and yang aspects – for example, light cannot exist without shadow. However, either of the two aspects may manifest more strongly in a particular object. Yin is represented as the feminine, passive, dark, cold, while yang is represented as masculine, active, light, warm. The sun is yang, the moon is yin – the yin and yang Chinese characters even contain the characters for moon 月 and sun 日.

This philosophy plays a significant role in Chinese culture, specifically traditional Chinese medicine and Chinese cuisine. In fact, Chinese medicine and food are intrinsically linked: Chinese practitioners suggest that a person’s health can be improved with a change in diet in order to restore a healthy balance between the yin and the yang in the body. The macrobiotics diet developed by American-Japanese writer George Othsawa is largely based on this philosophy.

Most foods can be separated into either being predominantly yin, predominantly yang or a balance between the two. These foods aren’t determined by their physical temperature; rather, they are determined by multiple characteristics. Generally speaking, foods that have a higher water content are considered cool, or yin, whereas foods that have a higher energy content, particularly from fat, are considered warm, or yang.

Soy products such as tofu and beansprouts, crab (such as the Shanghai hairy crab), most fruits, and vegetables such as watercress, cucumbers, carrots and cabbage are considered yin foods. Duck and beef, warm spices such as cinnamon, nutmeg and ginger, alcohol, nuts such as almonds and peanuts, eggs and glutinous rice are considered yang foods. Yin foods are generally bitter, salty and sour, while yang foods are generally sweet and pungent.