Gross, but thought-provoking
Kent Sepkowitz, writing for Slate, asks whether we might not be better off in terms of immunity by living under less sterile conditions. His recommendation to scientists: figure out if there's a level of excrement we can eat that would boost our immune systems without killing us. I imagine susceptibility varies by age, and I do know that we live longer as a population than we used to before sanitation. Other than that, I'm not a microbiologist, and I can't decide whether this idea is completely wacky or not.