Consubstantiation

The Lutheran doctrine of Consubstantiation means that at the words of consecration, the substance of the bread becomes Christ alongside the substance of bread.

This is problematic for a couple of reasons.

First, is that it is unscriptural. Christ said, "This is my body." He did not say, "This is my body and bread."
At the words of consecration, the substance is completely changed into the body of Christ. The substance is entirely Jesus with the accidents (appearances) of bread and wine. This is what is meant by the doctrine of Transubstantiation. Any other view of what happens at the words of consecration is unscriptural and a distortion of the Sacrament.

Another major problem with Consubstantiation concerns adoration of the Blessed Sacrament. When we adore Christ in the Blessed Sacrament, we give to Christ latria. Latria is adoration or worship reserved for God alone. If we adore the Blessed Sacrament and Consubstantiation is true, then we are committing partial idolatry. For we would be adoring Christ as well as the bread which remains alongside Christ in the host.