How do you know what you know about the medieval diet?

Answer 1

I read about from people who have made it their profession to know. There are recipes still around that were in use and historians have found various foods in many ways. Peoples bones can tell us how well they ate, what they ate, and when they died. Ancient people's are often buried with food products because it was believed that they needed to eat enroute to the afterlife. Residue of oils, wine, and other things have been found in pottery as well as shipments of sunken ships holding amphora. Paintings often feature food and people eating or working in fields. All of these things add up to learning and knowing how people lived and what they ate.