As the concept of sin has receded in American culture, the belief in body-poisons has grown. We are sure there is some pesticide, some hormone, some Frankenfood which is endangering us a little at a time, cumulatively eating away at our health. So many faddist health measures assure us that they flush various things from our bodies. We are walking bags of poisons inflicted on us by heartless corporations who only want to make money and don’t care what terrible things they do to us. Some conservation of belief in impurity seems in play here.
Also, it shows that we now value our body over our character.
Update: There is great similarity between extreme environmentlists and the early Puritans. Just a different target.