5 ideas
Renaissance dietetics held that each body has a distinct complexion, a balance of hot, cold, wet and dry qualities, and that foods carry these same qualities in measurable degrees. Correct eating meant matching or correcting one's complexion with foods of complementary qualities, so there was no universally good food, only food appropriate to a particular constitution.
Dietary writers argued that laborers had coarse, robust stomachs suited to heavy foods like dark bread, legumes and salt meat, while elites had delicate constitutions that required refined, easily digested foods. This turned a social hierarchy into a bodily fact, so eating 'above one's station' became medically dangerous rather than merely presumptuous.
Read nutrition advice as a record of who is writing and for whom, not only as neutral health guidance. The Renaissance diet books were written by physicians for courtly and urban elite patrons, so their categories of wholesome and harmful food track the audience's status concerns as much as any observed physiology.
Galenic regimen covered six controllable factors: air, food and drink, sleep and waking, exercise and rest, excretion and retention, and the passions of the soul. Diet books therefore treated eating as one lever within a total management of daily life, making health a matter of disciplined self-regulation that required leisure and means to practice.
Printed vernacular diet books spread medical knowledge beyond physicians to literate lay readers, letting individuals take charge of their own regimen. Yet the content often taught those readers which foods matched their rank, so wider access to expertise also spread the idea that bodies were fixed by social position.