Although Hippocrates (C. 400 B.C.) ascribed certain qualities to food and founded a dietetics based on personal observations and the accumulated knowledge of the era and although Erasistratus of Julius at Alexandria (C. 300 B.C.), "father of Physiology" traced hunger to an empty stomach, little was done in actual trials to determine the digestible nutrient value of foods.
Gillette, D. Dale
"A Short History of Early Digestion Trials,"
Iowa State University Veterinarian: Vol. 30
, Article 3.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol30/iss1/3