I read one of the answers about the parasites in pork rarely affecting humans if it is cooked properly. But that was one of the reasons it was called an unclean meat. They couldn't cook it properly and got ill. They linked that to God and you have an 'unclean meat' right there (there weren't complete idiots to science. Daniel even did a science experiment to show that eating vegetables was better than the "Royal food" provided by the King of Babylon ("Royal food" probably included unclean meats as Daniel didn't want to "defile" himself).
Anyway, about unclean foods: Many think the new Testament says that they can eat unclean meats, and it may well do. But, it would have to mention it after ACTS 10:9-28. Many misinterpret this passage, or may only read ACTS 10:9-16, which makes it sound like God saying you can eat clean meats. However, Peter (or had the vision) knew that this vision wasn't about food (in the vision he refused unclean meats while God said it was ok to eat them. The passage later says he thought about it twice, meaning he was unsure of the true meaning). He later met some gentiles, who, at that time, were considered unclean and Jews weren't meant to associate with them. Peter then realises that God meant that Jews should associate with gentiles, the true meaning of the vision.
If it says anything about eating unclean meat after that passage, then fine, but this passage shouldn't be cut up to get a false yet favourable meaning.
P.S. This was after Jesus said something like "what goes in the mouth leaves the body, but whatever leaves the mouth makes them unclean". The odd thing is, they weren't eating unclean food exactly. The Pharisees (the religious leaders), I think, complained that they didn't wash their hands before eating the food, which is what started Jesus' rant (this does tell us that Jesus, and God, obviously didn't know that bacteria existed and caused disease, but that's another argument). Besides, if unclean meat was allowed, why did Peter continue with the tradition?
I'd just like to add, the disease caused by poorly cooked pork is called Trichinosis. Its obviously safe today (aimed at the if the following precautions are taken:cooking it properly properly, keeping pigs in clean pens, preventing pigs from eating uncooked and infected animals, cleaning the grinders of previous pig meat, and destroying the actual parasite in infected meat (thank wikipedia).
Last addition: I KNEW someone would misinterpret Acts, but seeing as Colossians is later than Acts. Then that may override previous statements about the dietary laws.