600 – 400 B.C.
"Physicians from the Hippocratic School of medicine rejected notions that magical and supernatural influences determined human well-being." Through observation and logical reasoning they began to develop an understanding of the natural world and "recognised the recuperative powers of the body and the importance of food in maintaining or restoring health." They believed that human health was dependent on four mystical humours – blood, phlegm, black bile and yellow bile and their associated qualities: warm, cold, moist and dry.
Harper, A.E. (2000) Recommended Dietary Allowances and Dietary Guidance. Cambridge World History of Food. Cambridge University Press.
Early dietary fads have been linked back to around 500 B.C. Both warriors and athletes consumed certain foods to aid performance and strength. Favoured items were lion heart and deer liver.
Applegate, E.A. and Grivetti, L.E. (1997). Search for the competitive edge: a history of dietary fads and supplements. Journal of nutrition. Vol. 127. 869s-873s.