In the footnotes of the NAB translation of John 6 (Christ’s “I am the Bread of Life” discourse), it notes that in John 6:54-58, the original Greek verb for “eats” is NOT the generic word for human eating but the term which Greek speakers at the time of Christ used to describe animals devouring or gnawing on the flesh of their prey. The term obviously implies chewing.
In other words, if you translate those verses literally from the Greek, Christ says: “Whoever devours/gnaws/chews on my flesh and drinks my blood has eternal life…”
The footnote goes on to say that “This may be part of John’s emphasis on the reality of the flesh and blood of Jesus… but the same verb eventually became the ordinary verb in Greek meaning ‘eat’.”
However you translate it, it obviously sounded pretty shocking (and was meant to be shocking) to Christ’s original audience, as evidenced by the fact that many of his followers left him after that. In fact Christ then asked his own Apostles “Does this shock you?” (Jn. 6:61).
Given the fact that Christ Himself – as quoted by John the Evangelist – invited his own followers to “chew on” or devour his flesh, it seems kind of ironic that so many Catholics were raised on the notion that one should NEVER, ever, chew on or bite the Host!
Now I will admit that allowing the Host to dissolve on your tongue is much preferable to munching on it in a careless or obvious manner as if you were chewing gum – that DOES drive me nuts when I see it. Even at ordinary meals we are taught not to chew with our mouth open or in an exaggerated manner. Just out of charity, reverence, and good manners, it probably is best to avoid chewing the Host. However, the notion that it’s some kind of deadly sin or sacrilege if the Host touches your teeth is, IMHO, a bit extreme.