Forget the food groups or pyramid. Balanced diet, in those times, meant using food to balance the body’s proportion of hot, cold, wet and dry. The stomach was viewed as a cooking pot. In order to process what’s put into it, it needs heat. Putting in cold, wet foods will make the stomach unable to bring things to a boil. This, in turn, will make the body imbalanced, which is the root cause of illness.
Every food was considered to have a sort of valance measure for where it fit on the hot/cold, wet/dry spectrum. Some judgments were obvious, for example, a raw apple is obviously wet and cold. Other judgments were philosophically fanciful. Fire goes up into the air, birds fly, so poultry meat must be warm and dry. By contrast, pork was cool and wet, while beef was cool and dry. Lamb was warm and wet. Fish, especially eels, were cold and wet.
Cooks served meat with condiments to balance them. Serving mint jelly with lamb may come from an original need to “cool” its “warm” tendency. Pork and beef were served in spiced sauces in order to heat them up; pork needed to be heated and dried, so it called for the greatest spicing attention. Note that these qualities were not about literal temperature, though they believed it was better to eat warm food, for example, heated wine. Hot pork pie still needed cinnamon and pepper to warm and dry it; the food was equally balanced when served cold the next day. So each spice had a certain valence on the hot/cold, wet/dry scale. Pepper was hot and dry, as was cinnamon. Eel stew and lamprey pie had to be steeped in pepper and cinnamon. Ginger was considered hot and wet, making it the perfect seasoning for beef.
People were not all the same in constitution, either. Aristocrats kept personal physicians, university-trained, who could observe their skin, hair, personality, and urine in order to determine whether they need to be balanced away from one of these elements. The hot tempered needed to stay away from poultry and pepper, while sardonic, melancholy men had to avoid beef and fish. Young men were considered generally too hot, while old men were prescribed cinnamon and ginger to overcome the cooling effect of age.
Since all fruit was cold and wet, it had to be served cooked and spiced. Spiced apple rings, baked pears, pumpkin pie and cinnamon-flavored applesauce may be lingering holdovers from medieval fruit desserts. In order to keep the stomach at a nice boil, aristocrats ended their meals with spiced hot wine and candied whole spices.