For many years, it was believed that the main function of the large intestine was just to absorb water and dispose of waste, but “[n]owadays it is clear that the complex microbial ecosystem in our intestines should be considered as a separate organ within the body,” and that organ runs on a MAC, microbiota-accessible carbohydrates. In other words, primarily fiber. One reason we can get an increase of nearly two grams of stool for every one gram of fiber is that the fiber fermentation process in our colon promotes bacterial growth. The bulk of our stool by weight is pure bacteria, trillions and trillions of bacteria, and that was on a wimpy, fiber-deficient British diet. People who take fiber supplements know that a few spoonfuls of fiber can lead to a massive bowel movement, because fiber is what our good gut bacteria thrive on. When we eat a whole plant food like fruit, we’re telling our gut flora to be fruitful and multiply. From fiber, our gut flora produce short-chain fatty