According to the Late Antique authors, what was the basis of nutrition in ancient Rome?
Ancient Roman cuisine changed greatly over the duration of the civilization's existence. Dietary habits were affected by the political changes from kingdom to republic to empire, and the empire's enormous expansion, which exposed Romans to many new provincial culinary habits and cooking methods.
In the Imperial period, around the beginning of the Christian era, bread made of wheat was introduced; with time, more and more wheaten foods began to replace emmer loaves. There were many kinds of bread of differing quality. Typically white bread was baked for the elite, with darker bread baked for the middle class, and the darkest bread for the poor peasants.
In Ancient Rome, wine was normally mixed with water immediately before drinking, since the fermentation was not controlled and the alcohol grade was high. Wine was sometimes adjusted and "improved" by its makers: instructions survive for making white wine from red and vice versa, as well as for rescuing wine that is turning to vinegar.