הלכה על יומא 152:14

And it follows from the rule that a human being needs to direct his mind when eating (and this is of great benefit to the fulfillment of his intent), that he turn to “fine foods,” for by their fineness the intellect is refined and the heart made clear-sighted, as our sages said, “wine and fragrances made me clear-sighted,”⁶⁸B. Yoma 76b. and it is necessary to direct one’s mind to them only to make the eyes of the intellect clear-sighted, as I mentioned above. And one should beware of coarse foods, for the power of the intellect is clouded by them and its lucidity and refinement ruined. And already among our ancestors, so I have heard, that whoever did not eat beef because of its coarseness, but whose eating consisted mostly of small, delicate fowl, would raise them in their homes and feed them meals of ingredients known to them and which they themselves prepared for them, in order to refine their brains and make their organs right, which are the vessel of the soul, in order for the soul to be lifted up and develop the aptitude to receive the Torah and to understand the Holy One (may his name be blessed), for the intellect is sharpened and refined according to the fineness of the food and its purity. And this is a tried and tested thing among cosmopolitan people, and some village people, for cosmopolitan people whose foods are delicacies and whose drinks are fine and refined – are they not intelligent in every area, and quick to understand science with ease and without much effort, much more so than village people who eat barley and onions, and the rest of the coarse foods. Indeed the coarseness of their intellect follows the coarseness of their food. And the choicest of enjoyments, the pleasures of food were created only for the sake of the Torah, and for this reason they said in the Chapters of the Fathers: “If there is no choice flour, there is no Torah, and if no Torah, no choice flour,”⁶⁹M. Avot 3:17. that is to say, there would be no pleasures of food.