This seems to be a very misunderstood among the Christian community.
It is due to not understanding scriptures that were referencing other scriptures.
To explain this to my mother, I used some examples of meats and plants that are poisonous and therefore not edible in response to the scriptures that people think says you can eat whatever you want as long as you give thanks. In those scriptures, it say "that God created to be received...". So then, God did not create all plants and animals to be edible. You can eat nightshade and give thanks to God for it, but you will die as God did not create it to be eaten. So what are the scriptures referencing when saying "God created to be received..."? There is only one place that this is clarified and that is in the old testament.
People argue about this because there are things in the list that they like to eat. Pork for instance. I like bacon. God said that pork is unclean and was not created for consumption. Even modern science will tell you that pork is really bad for you. It should be good enough for us that God said it. I have finally given up pork and will live healthier and maybe longer as a result.
It wasn't until I noticed that doctors were in agreement (although they don't know) with the things listed as clean and unclean that I realized that God gave us a list for a healthy diet. Now if I could find his recipe for a milkshake to go along with it, I will be all set.
Anyways, instead of just directly answering your question, I thought I would rather just share information and let you decide on your own. I hope that any of this helps.
P.S. I have also noticed that the majority of the diet systems that exist actually follow the diet that God layed out for us. Interesting, huh.