Let's compare two translations of scripture:
Mark 7:18 (NIV) "Are you so dull?" he asked. "Don't you see that nothing that enters a man from the outside can make him 'unclean'?
Mark 7:19 (NIV) For it doesn't go into his heart but into his stomach, and then out of his body." (In saying this, Jesus declared all foods "clean.")
Mark 7:18 (KJV) And he saith unto them, Are ye so without understanding also? Do ye not perceive, that whatsoever thing from without entereth into the man, it cannot defile him;
Mark 7:19 (KJV) Because it entereth not into his heart, but into the belly, and goeth out into the draught, purging all meats?
Those two translations do not say the same thing. The King James does not have Jesus declaring all foods clean, in the biblical sense. It is saying all food passes through the body and is expelled. Jesus is not removing the prohibition on eating unclean animals. Modern translations like the NIV that say Jesus declared all foods clean are in error, and are intentionally mistranslated in order to justify eating the biblically unclean animals.