The Economist covers “the microbiome”, that is, the collection of bugs that live in our intestines and outnumber the cells of our bodies by a 10 to 1 margin:
Basically it boils down to this: you mess with the gut bugs, and the gut bugs will mess with you.
One interesting bit of trivia (which actually isn’t all that trivial): human breast milk is loaded with carbohydrates called glycans. However, the human body itself is 100% incapable of digesting glycans. We just can’t do it, at all. But the gut bugs can. And what’s really very cool is that the byproduct of bacterial processing of these glycans, as well as a lot of other complex carbohydrates, are small fatty acids, which happen to be ideal for the human digestive tract.
Suggested further reading on this subject on the Fat Head blog, which is where I found that link to the Economist article. There’s been a lot of discussion there lately about resistant starches, which ties in to gut bugs because you need gut bugs to digest resistant starches, and doing so ends up being extremely beneficial. See also the Free the Animal blog, the author of which is a strong proponent of resistant starches and the associated probiotics. I’ve been meaning to read up on that myself, actually. Over a year ago I went on a diet regimen that allowed me to lose about 60 pounds in maybe half a year, but I was tired and anxious all the time, and eventually the little lapses accumulated into big lapses and I ended up gaining it all back, plus now having digestive tract difficulties that are a notch or two worse than what I had before. Clearly there was something amiss in the regimen I used, and I’m about 99% sure it relates to the microfauna not getting what they needed. I suspect resistant starches may be the solution.