Reason Some Foods Unclean

Leviticus 11:46 This [is] the law of the beasts, and of the fowl, and of every living creature that moveth in the waters, and of every creature that creepeth upon the earth:
11:47 To make a difference between the unclean and the clean, and between the beast that may be eaten and the beast that may not be eaten.

Many articles of food eaten freely by the heathen about them were forbidden to the Israelites. It was no arbitrary distinction that was made. The things prohibited were unwholesome. And the fact that they were pronounced unclean taught the lesson that the use of injurious foods is defiling. That which corrupts the body tends to corrupt the soul. It unfits the user for communion with God, unfits him for high and holy service. {MH 280.4}