Yin and Yang
Yin represents Earth, feminine, dark, humidity, passiveness, while Yang symbolizes Heaven, masculine, dryness, warm, activeness. The Vietnamese try to apply the Yin-Yang theory to their cooking process in order to balance out all the ingredients; indeed, they believe balance is the key to
well-being in life. That is not an alien concept to the Western-Greek culture, since also Hippocrates asserted that disease was caused by an imbalance of the humors of the body. The difference in Asian culture is that balance also involves spiritual life, given that body and universe are interconnected.
Raw and cold foods, like vegetables and fruit, are always Yin, while wholegrain cereals, root vegetables, white meat, red meat and ripe cheese are Yang. It's no surprise that salad is mixed with chicken and shrimps together. Seafood, which is 'cold', is usually paired with ginger sauce, lemon grass sauce, lemon or chilli peppers (warm).