In John 6, the verb used to describe the Eucharist is not the the classical Greek verb used of human eating, φάγω, but that of animal eating, τρώγω, which literally means to “munch” or “gnaw”.

This is used by St. John to show the reality of the flesh and blood of Christ.

From John 6:54 on, Christ only uses the word τρώγων when referring to how believers will "eat" His flesh. A particularly interesting passage in John 6:58, where our Lord uses both φάγω and τρώγων together. The passage reads:

The verb "eat" is used twice here, once with reference to the Israelites eating the manna, the other to the faithful eating the Body of Christ. In this passage, Jesus uses φάγω when referring to the Israelites eating manna but again uses τρώγων when referring to Himself.

The meaning is plain; Jesus wants us to understand that we will "eat" His Body in the most literal, direct sense of the word.

This is why He uses the term σάρξ for flesh, which means a real and physical flesh, and τρώγων, akin to the English “masticate”, for eat.

Had He meant this teaching to be symbolic, it is hard to understand why He would have:

1. chosen such univocal terms when other more general terms were available that He had used on other occasions.

2. continued to stress the apparent literal truth of His statements to His scandalized listeners.

3. failed to offer any clarification or warning that His words were not to be taken literally, even when He had done this on other occasions.

Even when His own disciples start to desert Him, He does not modify or clarify this teaching in the least. This is odd, given the other occasions that He had corrected His disciples understanding of his words. If Jesus did mean these words symbolically, He would have said so.

The assertion that the eating of the flesh of the Son of Man in John 6 is symbolic simply doesn't hold weight when examined linguistically and in the context of other statements made by our Lord.