To the revealed Word that there is "Father, Son and Holy Spirit" the Church labeled the belief "Trinity."
To the revealed Word that the "Son of God became man" the Church labeled the belief "Incarnation."
To the revealed Word that the "blood of Christ spilled on Calvary saved us" the Church labeled the belief "Redemption."
To the revealed Word that "my flesh is true food, my blood is true drink" the Church labeled the belief "Transubstantiation."
Transubstantiation reflects Roman Catholic faith in the literalness of the words of the Bible.
Jesus (omnipotent God) said: "This is my body; this is my blood." And again Jesus said: "I am the bread of life;" "My flesh is true food; my blood is true drink;" "He who eats my flesh and drinks my blood ...;" etc.
Roman Catholics take Jesus at His word: the bread is his body; the wine is his blood.
From the Apostles at the Last Supper until today, the bread and wine of Eucharist looks and feels and tastes like bread and wine in the eating and drinking.
Similar to all of God's Word, faith is essential. Faith in what? In the words of Jesus even though the bread does not look, feel, taste like flesh; even though the wine does not look, feel, taste like blood.
Medieval philosophers and theologians sought simply to label this simple biblical faith: Jesus said that bread is his body and wine is his blood even though it did not appear to change into visible flesh and blood.
Transubstantiation means the substance part of the bread and wine elements changes; but the accidental parts--sight, taste, smell, touch--do not. Catholics believe that since Jesus said it and He is God, he can do it. They believe! "Transubstantiation" merely labels it.In everyday life, it is not at all uncommon to believe in things man cannot perceive by the senses: wind, electricity, love, peace, etc. All the more when Jesus says it.