Not only Catholics, but also Orthodox Christians, Lutherans and some Anglicans believe in the Real Presence of Christ in Holy Communion. And many Evangelical Christians are increasingly considering the possibility that the Historic Church got it right.
If we actually believed we received the Precious Blood of Jesus Christ on our lips from the Altar every Sunday or even daily, as often as we received Jesus into our hearts in Holy Communion, with what devotion we would worship! Imho, it is the solution to some of the closed and empty churches we see in parts of the world today, like in Europe. Rediscovering the Power of Christ's Blood in Holy Communion. The Lord's Word is Very Clear: His Flesh is Food indeed, and His Blood is Drink indeed. Whoever eats of it lives by Him.
Can those who believe Holy Communion is just a symbol explain
1 Corinthians 11? Here it is in the KJV:
"23 For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread:
24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
25 After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come.
27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord.
28 But let a man examine himself, and so let him eat of that bread, and drink of that cup.
29 For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body."
St. Paul the Apostle here teaches us that:
(1) If we eat the Bread and drink the Cup unworthily, we are guilty of the Body and Blood of the Lord. How is that possible if Communion is just a symbol? If I tear up a picture of your wife - which is just a symbol - am I guilty of the blood of your wife? Clearly not. It was just a symbol. In my opinion, therefore, 1 Cor 11:27 is a Strong Proof that Holy Communion is the Literal Blood of Jesus.
(2) Secondly, in verse 29, the Apostle plainly teaches us what we must do: we must discern the Lord's Body by faith in God's Word. A Medieval Christian Theologian St. Thomas Aquinas said: "I believe everything the Son of God has said; nothing is truer than Truth's own Word". His point was we don't go by sight or taste or touch or smell etc here, but only by what God said "This is My Body".
Even Martin Luther used a similar argument in a Public Disputation with one of the other Reformers. I believe it was Calvin or Zwingli.
When God said "Let there be Light", immediately Light was made. When God says "This is My Body", it immediately changes into His Body. He then gave His Apostles the Command and the Power to do the same in His Name until the end of time when He returns.
Also, why should it be thought incredible, that God can change Wine into Blood? Didn't He change water into wine at Cana?
Finally, the Real Presence has sometimes been confirmed by miracles to "doubting Thomases", just like the Resurrection was. Even Atheistic Scientists have become believers in the Lord Jesus upon seeing these miracles. More on that here:
http://www.therealpresence.org/eucharst/mir/lanciano.html
God Bless.