Transubstantiation is the doctrine of the Roman Catholic Church which, since the thirteenth century, has stated that during the consecration of the sacrificial offerings of bread and wine at the Mass, that the bread and wine are literally changed into the body and blood of Christ. Transubstantiation holds that while the outward, sensible characteristics of the bread and wine remain, the actual substance or reality is transformed into the substance of Christ. It should be noted also that Christ's body and soul are united in Heaven and cannot be separated, so that not only the body and blood, but the soul and divinity--in short, the whole substance of Christ--are believed to be made present under the appearance of ordinary bread and wine.
This is a view that contrasts with the beliefs of the Protestant churches. Most of the Reformers during the Protestant Reformation taught one version or another of the "Real Presence" in the Eucharist, instead of a purely symbolic view. In the Lutheran, Reformed, Presbyterian, and Anglican churches, the doctrine of the Real Presence is affirmed, but not the additional doctrine called Transubstantiation.
In other words, those churches accept that Christ's body and blood are truly present in the Eucharist or Lord's Supper, but not that the bread and wine consumed by the minister and the congregation alike have ceased to be bread and wine.
For other Protestants (mostly Evangelical, Fundamentalist, and Pentecostal) who also celebrate Christ's Last Supper, the belief is that the wine and bread merely symbolize or represent the body and blood of Jesus.
Transubstantiation was a contentious issue during the Protestant Reformation, a historical period of conflict and warfare among Christians over a number of issues of scriptural interpretation, doctrine, philosophy, and both ecclesiastical and secular politics.
The Bible and Transubstantiation
Catholics believe the doctrine of Transubstantiation can be validated by Scripture.
In John 6, Jesus promises to His followers the Bread of Life, His flesh. (John 6:51) When the Jews began to argue over how Jesus could give them His flesh, He responded by repeating the necessity of doing so: “Unless you eat the flesh of the Son of Man, and drink His blood, you have no life within you” (John 6:53). When His disciples said “This is a hard teaching; who can follow it?” (John 6:60), Jesus allowed them to go and even asked His 12 apostles if they too would leave. Catholics note that Jesus did not claim to be speaking symbolically or metaphorically when His disciples left, even though they seemed to take Him literally. Thus, it is concluded, Jesus was speaking literally. Then, at the Last Supper when He said “This is my body” and “This is my blood,” He was fulfilling His literal promise made in John 6:51, according to Catholics, to give His followers His body and blood.
As noted above, most Protestants do not dispute the fact that Jesus intended to give his body and blood to his followers. That is not the issue involved in the doctrine called "Transubstantation."
As to whether or not the Communion bread and wine cease to be bread and wine (i.e. Transubstantiation, a change-over of substance into another substance) while taking on the presence of Christ, Protestants maintain that there is no Biblical evidence which supports that speculation.