If the Holy Communion is really Christ in the flesh, why does he need to be consumed? How does consuming Jesus' flesh contribute to salvation if we have already received the Holy Spirit?

Radically non-traditional views are expressed below.

Eating the flesh and drinking the blood of Jesus, as in John 6, is not the same experience as eating the bread and drinking the wine, as in the synoptic Gospels at the Last Supper.

Only the John 6 experience gave life, and it was an experience given to only one person, the one that was lost, whom Jesus raised up again at the last day. The life giving flesh and blood of Jesus was consumed once, by one, for all.

The Synoptic experience of eating the bread and drinking the wine is just a commemorative act, which Jesus commanded his disciples to do in remembrance of him. The disciple is to remember Jesus as often as he eats and drinks.

As the food of Jesus was to do the will of his Father, and to finish His work, so the food which Jesus gave consisted of doing his will, and of cooperating with him as he finished the work of his Father. That food was consumed by Judas Iscariot, once, and for all.