I would think that slow cooking porridge overnight would make it as unhealthy as fully processed Pabulum, Mr. Red. Rolled oats are already cooked when they are rolled. They are not as nutritious as the oats that our Scottish ancestors carried in their pockets and chewed on all day. To get half the benefit the old folks got from oats, you need to treat them with respect, not cook them too much. Keep them big and chunky so that they feel like a front-end loader rolling down your lower intestine.