"Excess dietary fiber. (Yes, you’re reading it right.) The by-products of fiber’s bacterial fermentation (short chain fatty acids, ethanol, and lactic acid) destroy bacteria for the same reason acids and alcohols are routinely used to sterilize surgical instruments—they burst bacterial membranes on contact. And that’s how fiber addiction develops: as the fermentation destroys bacteria, you need more and more fiber to form stools. If you suddenly drop all fiber, and no longer have many bacteria left, constipation sets in as soon as the large intestine clears itself of the remaining bulk."