This Slate article suggests that Americans should consume a bit more waste in our diets. The theory behind this is that the near-surgical level of cleanliness that many kids experience these days make them like the boy-in-the-bubble, with weak immune systems. So when a bit of infected food makes it through, it can be fatal. I don't have the scientific expertise to evaluate this claim, but I just love counterintuitive stuff like this.
By the way, didn't George Carlin advance a similar theory?