I think it is safe to say that a common Protestant position with respect to John 6:48ff. is that eating Christ’s flesh and drinking His blood is a metaphor for coming to and believing in Him. To eat Jesus’ flesh and to drink His blood is said to produce the same contextual effect as looking on or believing in the Son (6:40; 54); in both cases the individual has eternal life and will be raised the last day. Further, the eating of His flesh and drinking of His blood and coming to or believing in Christ are each compared with the bread which the ancestors of Jesus’ audience ate (6:28-35; 58). At any rate, such observations are not new.
Years ago – before updates made discussion on facebook groups almost completely undesirable – I debated Roman Catholics on a whole host of issues, one of which was transubstantiation. Now, anyone who has discussed this subject with Roman Catholics is probably aware of what they think about John 6: it’s safe to say the vast majority think Jesus is referencing the Eucharist. To buttress their doctrine of transubstantiation, they then argue that Jesus intended to convey to His audience that they ought to literally eat His flesh and drink His blood. I came to find that one of the usual arguments in favor of this is that one of the Greek words Jesus uses to refer to the act of eating His flesh, trōgō (John 6:54, 56-58), is never used figuratively.
However, this word is only found in only two other verses in the New Testament (John 13:18 and Matthew 24:38). A purely inductive argument would not seem to make for a very strong case that trōgō can’t function metaphorically. And as D. A. Carson notes on pg. 296 in his commentary on John (which is what brought this subject to my mind):
In v. 54 and again in vv. 56, 57, 58, the verb for 'to eat' becomes trōgō (as opposed to esthiō, or more precisely its aorist stem phag-, the customary verb found elsewhere in this passage). In earlier Greek, trōgō was used for the munching of (especially herbivorous) animals; from the classical period on, the verb was also used of human beings. Some have taken its presence here as a sign of the literalness of ‘eating’ that occurs in the eucharist. It is far more likely that John injects no new meaning by selecting this verb, but prefers this verb when he opts for the Greek present tense (similarly in 13:18).