Galen believed that different foods influenced different humors. Warm foods, for example, tended to produce yellow bile, while cold foods tended to produce phlegm. There are other factors to be considered as well, such as : seasons of the year, periods of life, geographic regions and occupations.
If the humours were in balance, the person got good health ( or eucrasia). An ideal temperament involved a balance of the 4 qualities. ( warm, cold, moist and dry).
He believed each humour represented a quality, sanguine (blood humour), choleric (yellow bile humour), melancholic (black bile humour) and phlegmatic (phlegm humour)