What observation did Hippocrates famously make about individual diet appropriateness?

What is appropriate for one person might be harmful to another.

Ancient figures like Hippocrates recognized the variability in how different people respond to food long before modern technology existed. His observation highlights the fundamental principle that diet is highly individual specific. This early understanding relied heavily on careful observation, intuition, and broad categorization based on factors like a person's constitution and activity level. This contrasts sharply with the modern phase, which seeks to quantify these differences using molecular and genomic data, although the core idea of individual response remains constant.