In the Old Covenant, God gave many food laws to Israel. They were forbidden to eat certain animals that were deemed “unclean” by God. Why they were considered unclean isn’t clear, but what is clear is that God gave these laws to train the people of God to be able to make a distinction between what is clean and unclean so that they can be Holy as God is Holy.(Leviticus 11:46, 47) So the food laws were part of their training to be Holy.
In the New Covenant, all believers are called saints, that is, holy ones. Believers are holy based on their faith in Christ and the indwelling of the Holy Spirit. Accordingly, God does away with the food laws in Acts 10 when Peter sees the vision of the sheet coming down from heaven. In the sheet are all kinds of “unclean” animals that the Lord tells Peter to eat. Peter refuses saying he has been faithful to the food laws and never eaten anything unclean. God responds and declares, “What God has cleansed, do not call unclean.” This was a real change in the law. This taught Peter that the Gentiles, who eat unclean things, are full members of the body of Christ.
Food is still very important in the New Covenant. But now, all food is to be enjoyed in faith to the glory of God and for the edification of the body of Christ. Food takes on deeper meanings in the New Covenant, as well. Jesus says His food is to do the will of the Father. He also compares the Word of God to food and even says that His own body is food and drink, referring to communion. Ultimately the body and blood of Christ is the food of the New Covenant, the fulfillment of the Old Covenant food laws. As such, communion is now what makes the distinction between those who are “clean” in Christ and those who are “unclean” being reserved for eternal judgment.