Early Medieval Irish literature contains detailed information about food rents in premonetary economic systems based on clientage relations. Clients had to pay their patrons for a loan (a “fore-payment”) of a certain value, an exactly defined annual rent consisting of agricultural resources and prepared foodstuffs. Itinerant patrons consumed at least parts of this rental income, more or less immediately when it was delivered, at “feasts”, customary events characterised by a particular feasting culture. The texts also tell us about rules for the sustenance of the sick and the injured, who were entitled to a legally defined “healthy” diet graduated by social rank. In all of these texts, however, agricultural resources and foodstuffs served as a means of payment in a defined, pre-monetary system of established exchange value relations. This contribution examines these texts and develops a general model of foodstuffs as an established exchange value system and their consumption in pre-monetary societies.