Let the food be your medicine is a quote attributed to Hippocrates. The more accurate quote appears to be:
“Let food be thy medicine and medicine be thy food.” — Hippocrates, father of medicine, 431 B.C.

He is called the father of modern medicine and also, the oath that doctors take to be doctors is called the Hippocratic Oath.

People like Charlotte wonder why modern doctors do not heed the words of Hippocrates and have more focus on nutrition. This sentiment has been around for a long while, here are but two examples:

“The doctor of the future will no longer treat the human frame with drugs, but rather, will cure and prevent disease with nutrition.”

Thomas Edison

“He that takes medicine and neglects diet, wastes the time of his doctor.”

Ancient Chinese Proverb