Jesus offers one of several replies. He reminds us that the bread and wine of Holy Communion provide us the food and drink needed for eternal life.
The mystery of Holy Communion is something we accept, knowing we cannot offer sufficient explanation. Those who ask for or insist upon a full analysis will remain confounded and disappointed. We do know (nor do we really care) how God does this. It is something which we experience and receive and for which we give thanks.
Two days ago I found myself in a phone conversation. My conversation partner wasn't sure about this or that one-line statement of Christian creeds. In just a few brief moments, we explored the limits of language to capture the meaning and purpose of those one-liners.
The whole of Christian faith is too vast and too deep for total comprehension. It is not our place to understand, it is our opportunity to receive the assurances delineated in those proclamations of faith.
I will never understand the whole body and blood thing - but I am continually strengthened by the assurance that God would give anything in order for me to have the one thing I need.