“Regardless of the issues with defining and measuring dietary fiber, if you examine the Nutrition Facts Labels of many packaged foods, you will find that dietary fiber is lacking in much of what we normally eat. Packaged foods made with refined flour and copious amounts of added sugars provide no sustenance for the microbiota and likely translate into guts populated by starving microbes. The FDA recommends that an adult male consume 38 grams of dietary fiber per day while a woman should consume 29 grams. Despite these recommendations, the average American consumes a measly 15 grams of dietary fiber per day, a deficiency that is undoubtedly contributing to the malformation of the Western microbiota. While images of emaciated microbes may be floating through your mind, this is not strictly the case: bacteria can be extremely resourceful in their dietary-fiber-deprived state. That is because they have another source of carbohydrates, our intestinal mucus. During times of low fiber consumption, gut bacteria can sustain themselves on the carbohydrates that our intestinal cells continually secrete into the gut environment, which serves as a barrier to protect our own human cells from direct contact with the microbiota. But by feasting on mucus carbohydrates, our microbes deplete the protective gut mucus layer, compromising barrier function and increasing inflammation. While the long-term effects of less gut mucus on human health are still unknown, preliminary experiments suggest that loss of intestinal mucus can lead to colitis. But the microbiota is very adaptable: provide sustenance in the form of dietary fiber and many microbes will switch their focus from eating your mucus to eating your most recent meal.”