If you have the shits that long you might want to go see a doctor about it.

For a bit of relief, brewer's yeast is fantastic. It's the flaky, yellow kind sold at health food stores. It is also highly nutritious. It is the best thing EVER sprinkled on buttery popcorn!

If it's a lactose problem, lactase enzyme tablets with any dairy product are going to help. An organic farmer buddy of mine told me the other day that pasteurized dairy products are far less digestible than raw milk- you know, the way it comes out of a cow's tit, not heated and sterilized!- raw milk still. contains the enzymes that a calf needs to properly digest it.

Have some organic yoghurt with live cultures. They're good for settling digestive problems.