What the Bible has to say about it:
(Taken today from the New American Standard Version. All emphasis mine.)
(It's long, I know. But totally worth it.)
John 6:26-69 Jesus answered them and said, “Truly, truly, I say to you, you seek Me, not because you saw signs, but because you ate of the loaves and were filled. 27 Do not work for the food which perishes, but for the food which endures to eternal life, which the Son of Man will give to you, for on Him the Father, God, has set His seal.” 28 Therefore they said to Him, “What shall we do, so that we may work the works of God?” 29 Jesus answered and said to them,“This is the work of God, that you believe in Him whom He has sent.” 30 So they said to Him, “What then do You do for a sign, so that we may see, and believe You? What work do You perform? 31 Our fathers ate the manna in the wilderness; as it is written, ‘He gave them bread out of heaven to eat.’” 32 Jesus then said to them, “Truly, truly, I say to you, it is not Moses who has given you the bread out of heaven, but it is My Father who gives you the true bread out of heaven. 33 For the bread of God is [i]that which comes down out of heaven, and gives life to the world.” 34 Then they said to Him, “Lord, always give us this bread.”
35 Jesus said to them, “I am the bread of life; he who comes to Me will not hunger, and he who believes in Me will never thirst. 36 But I said to you that you have seen Me, and yet do not believe. 37 All that the Father gives Me will come to Me, and the one who comes to Me I will certainly not cast out. 38 For I have come down from heaven, not to do My own will, but the will of Him who sent Me. 39 This is the will of Him who sent Me, that of all that He has given Me I lose nothing, but raise it up on the last day. 40 For this is the will of My Father, that everyone who beholds the Son and believes in Him will have eternal life, and I Myself will raise him up on the last day.”
41 Therefore the Jews were grumbling about Him, because He said, “I am the bread that came down out of heaven.” 42 They were saying, “Is not this Jesus, the son of Joseph, whose father and mother we know? How does He now say, ‘I have come down out of heaven’?” 43 Jesus answered and said to them, “Do not grumble among yourselves. 44 No one can come to Me unless the Father who sent Me draws him; and I will raise him up on the last day. 45 It is written in the prophets, ‘And they shall all be taught of God.’ Everyone who has heard and learned from the Father, comes to Me. 46 Not that anyone has seen the Father, except the One who is from God; He has seen the Father. 47 Truly, truly, I say to you, he who believes has eternal life. 48 I am the bread of life. 49 Your fathers ate the manna in the wilderness, and they died. 50 This is the bread which comes down out of heaven, so that one may eat of it and not die. 51 I am the living bread that came down out of heaven; if anyone eats of this bread, he will live forever; and the bread also which I will give for the life of the world is My flesh.”
52 Then the Jews began to argue with one another, saying, “How can this man give us Hisflesh to eat?” 53 So Jesus said to them, “Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in yourselves. 54 He who eats My flesh and drinks My blood has eternal life, and I will raise him up on the last day. 55 For My flesh is true food, and My blood is true drink. 56 He who eats My flesh and drinks My blood abides in Me, and I in him. 57 As the living Father sent Me, and I live because of the Father, so he who eats Me, he also will live because of Me. 58 This is the bread which came down out of heaven; not as the fathers ate and died; he who eats this bread will live forever.”
59 These things He said in the synagogue as He taught in Capernaum.
60 Therefore many of His disciples, when they heard this said, “This is a difficult statement; who can listen to it?” 61 But Jesus, conscious that His disciples grumbled at this, said to them, “Does this cause you to stumble? 62 What then if you see the Son of Man ascending to where He was before? 63 It is the Spirit who gives life; the flesh profits nothing; the words that I have spoken to you are spirit and are life. 64 But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who it was that would [j]betray Him. 65 And He was saying, “For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father.”
66 As a result of this many of His disciples withdrew and were not walking with Him anymore. 67 So Jesus said to the twelve, “You do not want to go away also, do you?”68 Simon Peter answered Him, “Lord, to whom shall we go? You have words of eternal life.69 We have believed and have come to know that You are the Holy One of God.”
1 Cor 11:28-30 But a man must examine himself, and in so doing he is to eat of the bread and drink of the cup. 29 For he who eats and drinks, eats and drinks judgment to himself if he does not judge the body rightly. 30 For this reason many among you are weak and sick, and a number[a]sleep.
(A note on this. This is more about examination of sins, but the point here is that, why would it matter whether or not we eat the bread if it is just a symbol?)
1 Cor 10:16-17 Is not the cup of blessing which we bless a sharing in the blood of Christ? Is not the[a]bread which we break a sharing in the body of Christ? 17 Since there is one [b]bread, wewho are many are one body; for we all partake of the one [c]bread.
Luke 22:19-20 And when He had taken some bread and given thanks, He broke it and gave it to them, saying, “This is My body which is given for you; do this in remembrance of Me.”> 20 And in the same way He took the cup after they had eaten, saying, “This cup which is poured out for you is the new covenant in My blood.
1 Corinthians 11:30 I.e. are dead
a, b, c, lit. loaf