A close correlation between food and health is seen in the presence of a large number of Medieval recipes of foods for the sick. Lots of these are based on milk, chicken and rice (not shown, but central to the diagram). The ubiquitous "blanc mange", which is usually a chicken and rice dish made with milk (almond or cow milk), is perfect for the ill or infirm, and is clearly based on an attempt to balance the humours at source.
Building on this, we can see how some dishes are balanced by their ingredients. There's a Medieval sweet and sour rabbit recipe that draws on rabbit (hare), carrots (vegetables) to balance the moistness of onions, while the sweet and sour flavour (a very common flavour in Medieval food) stems from a combination of sugar and vinegar. In the correct proportion, while the range of tastes is quite dramatic, the resultant dish should sit comfortably in the middle of the diagram.
It was believed that cooking techniques naturally altered a food's temperament. Roasting warmed and moved a food towards fire, while boiling was moister, so boiled foods warmed and tended towards air. Covered pies and baking lay somewhere inbetween. It should come as no surprise to see that dry meats such as beef were preferably boiled, to increase their moisture, while moist meats such as pork were roasted. Fish (like onions) were fried to help dry them, and for many fish (especially the "dangerous" ones like eels and lampreys, being so phlegmatic) the application of salt or wine - a similarly dry and warm product - was often a vital part of the preparation process. Indeed, wine was often used to soak dead lampreys in, in order to counter the extreme cold moistness of that fish. Similarly, one writer insists that eels should be killed in a dish of salt and left to soak in saline for three days.
Vegetables, being earthy and dry, were usually boiled. Fruit, meanwhile, was regarded as excessively moist. It could be eaten raw, but preferably with old cheese and with wine nearby for balance. An alternative appears in a traditional fried bean and fruit recipe which includes plenty of dried herbs to counter the moistness of the fruit.