Question: A friend, who happens to be Roman Catholic, told me that their priest, when conducting the communion service, has the power to turn the wine into the actual blood of Jesus Christ. Also, that the wafer becomes the literal flesh of Jesus’ body. Does the Bible support or refute this practice?
Answer: What your friend told you is exactly what the Roman Catholic Church teaches. Their usual reference is to John 6:54:
"Whoso eateth my flesh, and drinketh my blood, hath eternal life: and I will raise him up at the last day."
If this teaching were true, it would be nothing more than cannibalism. All one has to do to understand what Jesus meant when he said, "eat my flesh and drink my blood," is to read the surrounding verses. He did not offer them His physical body to eat from; nor did He cut a vein and fill a cup with His literal blood for them to drink.
Christ, Himself, explains what he meant by that statement in Verses 40 and 47,
"And this is the will of him that sent me, that everyone which seeth the Son, and BELIEVETH ON HIM, may have everlasting life: and I will raise him up at the last day." (40) "Verily, verily I say unto you, He that BELIEVETH on me hath everlasting life." (47)
Jesus was simply telling them that He, as the symbolic "Bread of Life," was going to give His flesh and blood upon the Cross as the perfect sacrifice for the sins of the world. Therefore, anyone who would believe in Him as their personal Savior would never perish, but have eternal life. This is further substantiated at the Last Supper.
"And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take eat; this is my body." And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it. For this is my blood of the new testament, which is shed for many for the remission of sins."‑ Matthew 26:26-28
The bread and the "fruit of the vine" (v.29), when partaken of at communion, are only symbolical of the real body and blood of Christ which He sacrificed at Calvary.
I have personally talked with hundreds of Catholics through the years, and very few comprehend this belief that the "fruit of the vine" and the bread actually turns into literal flesh and blood of Christ when taken at communion. I have many Catholic friends and have asked them if the bread and wine has tasted any differently, as...similar to human flesh or human blood. I have never found anyone who said it did.
This practice by Roman Catholicism is termed "Transubstantiation." Their terminology for the Lord’s Supper is "Eucharist" which comes from the Greek word "eucharistia" and is translated "thanksgiving" in 2 Corinthians 4:15, "giving of thanks" in Ephesians 5:4, and "thanksgiving" in Colossians 2:7 (as well as many other places in the New Testament.