Under the strict dietary laws, lawful food is called Kosher in Judaism and Halal in Islam. Both religions prohibit the consumption of pork. The Christian Bible also forbids it.
A common explanation to the fact that pigs/swine/pork is widely considered unclean, or unfit for humans is that they are omnivorous, not discerning between meat or vegetation in their natural dietary habits. The willingness to consume meat (carrion) sets them apart from most other domesticated animals which are commonly eaten (cows, horses, goats, etc.) who would naturally eat only plants.