Prehistoric
".As food is a basic biological necessity, our early ancestors undoubtedly learned through observation and much trial and error how to identify safe sources of nutriment from among the vat array of natural products available to them. They discovered that some of these products were toxic and caused illness and even death. At the same time, they learned how to cope with several potentially dangerous foods and other dietary problems.Oral transmission of such information can be viewed as the earliest form of dietary advice."
Harper, A.E. (2000) Recommended Dietary Allowances and Dietary Guidance. Cambridge World History of Food. Cambridge University Press.