The Eucharist has always been an official doctrine. Have you ever read the Didache? It was written before the year 100 AD.
http://www.earlychristianwritings.com/text/didache-roberts.html
Here is section 9:
Chapter 9. The Eucharist. Now concerning the Eucharist, give thanks this way. First, concerning the cup:
We thank thee, our Father, for the holy vine of David Thy servant, which You madest known to us through Jesus Thy Servant; to Thee be the glory for ever..
And concerning the broken bread:
We thank Thee, our Father, for the life and knowledge which You madest known to us through Jesus Thy Servant; to Thee be the glory for ever. Even as this broken bread was scattered over the hills, and was gathered together and became one, so let Thy Church be gathered together from the ends of the earth into Thy kingdom; for Thine is the glory and the power through Jesus Christ for ever..
But let no one eat or drink of your Eucharist, unless they have been baptized into the name of the Lord; for concerning this also the Lord has said, "Give not that which is holy to the dogs."
And here is Saint Ignatius of Antioch, writing in the year 110 AD:
"They abstain from the Eucharist and from prayer, because they do not confess that the Eucharist is the flesh of our savior Jesus Christ, flesh which suffered for our sins and which the Father, in his goodness, raised up again... Let that be considered a valid Eucharist which is celebrated by the bishop, or by one whom he appoints. Wherever the bishop appears, let the people be there; just as wherever Jesus Christ is, there is the Catholic Church." (Epistle to the Smyreans)
"Take heed, then, to have but one Eucharist. For there is one flesh of our Lord Jesus Christ, and one cup to [show forth] the unity of His blood; one altar; as there is one bishop, along with the presbytery and deacons, my fellow-servants: that so, whatsoever you do, you may do it according to [the will of] God." (Epistle to the Philadelphians)
Doctrine is by an official pronouncement of the pope not a book.
It was not declared official and binding doctrine until 1215, until then those that believed it was a remembrance or spiritual presence were allowed.
"Elsewhere the Lord, in the Gospel according to John, brought this out by symbols, when He said: 'Eat ye my flesh, and drink my blood,' describing distinctly by metaphor the drinkable properties of faith and the promise, by means of which the Church, like a human being consisting of many members, is refreshed and grows, is welded together and compacted of both,--of faith, which is the body, and of hope, which is the soul; as also the Lord of flesh and blood. For in reality the blood of faith is hope, in which faith is held as by a vital principle." - Clement of Alexandria (The Instructor, 1:6)
"He says, it is true, that 'the flesh profiteth nothing;' but then, as in the former case, the meaning must be regulated by the subject which is spoken of. Now, because they thought His discourse was harsh and intolerable, supposing that He had really and literally enjoined on them to eat his flesh, He, with the view of ordering the state of salvation as a spiritual thing, set out with the principle, 'It is the spirit that quickeneth;' and then added, 'The flesh profiteth nothing,'--meaning, of course, to the giving of life. He also goes on to explain what He would have us to understand by spirit: 'The words that I speak unto you, they are spirit, and they are life.' In a like sense He had previously said: 'He that heareth my words, and believeth on Him that sent me, hath everlasting life, and shall not come into condemnation, but shall pass from death unto life.' Constituting, therefore, His word as the life-giving principle, because that word is spirit and life, He likewise called His flesh by the same appellation; because, too, the Word had become flesh, we ought therefore to desire Him in order that we may have life, and to devour Him with the ear, and to ruminate on Him with the understanding, and to digest Him by faith. Now, just before the passage in hand, He had declared His flesh to be 'the bread which cometh down from heaven,' impressing on His hearers constantly under the figure of necessary food the memory of their forefathers, who had preferred the bread and flesh of Egypt to their divine calling." - Tertullian (On the Resurrection of the Flesh, 37)
"'He that eateth me,' He says, 'he also shall live because of me;' for we eat His flesh, and drink His blood, being made through His incarnation and His visible life partakers of His Word and of His Wisdom. For all His mystic sojourn among us He called flesh and blood, and set forth the teaching consisting of practical science, of physics, and of theology, whereby our soul is nourished and is meanwhile trained for the contemplation of actual realities. This is perhaps the intended meaning of what He says." - Basil (Letter 8:4)