Musar על אבות 3:3

הנני ממטיר לכם לחם מן השמים … למען אנסנו הילך בתורותי. This verse contains an indirect instruction to say a word of Torah during meals.

Rabbi Arama further refers to his commentary on the phenomenon of Moses going without food or drink [chapter 32] in which he states that the more refined the food, the more it can serve as soul-food. This is the meaning of the concept of ריח ניחוח, the almost totally intangible part of food. "Man does not live on bread alone, but on all that emanates from the mouth of the Lord" (Deut. 8,3) i.e. one can live on spiritual nourishment. This is the reason that a meal during which no words of Torah are spoken is considered an abomination (Avot 3,3).