Before the eighteenth century, most people were concerned with simply getting enough to eat.  As advances in farming provided enough food for all, physicians searched for the healthiest diet.  Without an understanding of vitamins, nutrition requirements, and the process of digestion, many doctors thought diseases were caused by imbalances in the body’s fluids, and they advised patients to match foods carefully to their individual temperament and constitution. 

By the early twentieth century, scientists had learned more about nutrition, but even then, the role of vitamins and other nutrients was yet to be discovered.