Everything was created by the word of God. Divine words are what grant food the vitality to nourish us. One who makes a blessing on his food evokes the spiritual force within it. But if a person eats without making a blessing, even though he is nourished by the spiritual force within that food, he does not gain from it in the same way as one who makes a blessing.

The divine words that are within our food replenish us:

“Man does not live by bread alone; rather, it is by everything that issues from the mouth of the Lord that man lives” (Deuteronomy 8:3); this refers to the statements that issued from God’s mouth during Creation to extract each thing from the earth. Those [divine] words enter the food and nourish and give life to the person.

Making a blessing over food evokes the spiritual force that is within it:

Therefore, one must make blessings over food, because through the blessing, the spiritual force is evoked…. When one eats without a blessing, the spiritual force within it is not evoked. Eating…without a blessing does nourish part of the person’s soul, but the good that is brought upon the soul when there is no blessing is not the same as the good that results when a blessing is recited. (Rabbi Yitzĥak Luria (Arizal), Likutei Torah, Ekev)

The entire world was created via the power of the Torah, and therefore the spiritual force of everything lies within the Torah. One who reflects on a food’s spiritual force can be satiated by it, but one who sees only the physical aspect of the food cannot reach this state.

The central component of bread and other foods is the spiritual force within them, as it is stated, “There is no bread but Torah” (Midrash Tehillim 41:7). Everything was created through the power of the Torah, and the spiritual force of everything is found in the letters of the Torah. But one’s satiation [as a result of eating] depends on his outlook…. If he sees and believes that the spiritual force comes from the Torah and from the Holy One, blessed be He, then his soul receives the spiritual force [that is within the food], as the verse states (Proverbs 20:13), “Open your eyes; you will be sated with food.” (Rabbi Yehuda Aryeh Leib Alter, Sefat Emet, Beshalaĥ 5654)