We should all try to get more fiber into our diet. As dietary advice goes, is one of the things we put into the “duh!” category along with drink more water and eat your greens. We all know it’s important, but why? And then, when you look at ‘fiber’ you quickly realize that it’s much more complex than just ‘fiber’. There are different types from different sources and they all have their different effects. How much? What type?The “why” of fiber is the simplest answer. Fiber makes your digestive tract work right, which makes a number of other issues resolve. Many chronic degenerative diseases, like autoimmune disease, osteoarthritis, diabetes, or cancer, can trace their origins to a dysfunction in the gut. Fiber gives bulk volume to the stool, and when balanced with adequate water will drive the movement of stuff through your bowel. Remember, the stool is how we get rid of toxins, so you don’t want it hanging around too long. But it also doesn’t want to go too quick, lest we lose water and nutrients. We want it just right, a balance of fiber, water, food and bacteria to digest, ferment, absorb and eliminate.Wait, what? Ferment? That’s how beer is made. Yes, but it’s also how the gut bacteria work. Fiber comes in two basic types, soluble and insoluble (in water), neither of which is digestible by our guts. We have developed a symbiotic relationship with our gut flora, we give them a home and food, and they ferment fiber to produce Short Chain Fatty Acids (SCFAs). SCFAs are food both for the bacteria and for us. Bacteria also produce vitamins, maintain the pH, control bad bacteria and a host of other things we are learning more about every day.Bacteria ferment about half of the fiber we eat. The rest does different things depending on the type. Both types will add bulk to the stool, increasing fullness and stimulating enzyme production. Both types will also delay gastric (stomach) emptying, which aids digestion and moderates the effect of food on blood sugar. Insoluble fiber (cellulose) stays mostly in this realm.Soluble fiber is a bit more complex. Soluble fiber can be hemicellulose, mucilages, gums, pectins or fiber compounds. Oat bran is the best example of hemicellulose, and has been shown to lower cholesterol levels. Mucilages are found in the inner parts of seeds, nuts and beans, and will form a thick gel in water. The gel is the best at increasing satiety which slows the absorption of sugars, and aids in the treatment of diabetes. Gums are resins from a plant. Pectins come from the skins of fruits and vegetables. Many soluble fibers bind with cholesterol and can aid in maintaining healthy cholesterol levels. Your doctor may use specific fiber supplements for treating different conditions.Fortunately, fiber doesn’t need to be fully understood to be eaten as a beneficial food. Most plants are a mix of both types if fiber. Eat a variety of plant-based foods. A diet high in starchy staples (whole grains) with a variety of tubers, vegetables, fruit, legumes, nuts, and seeds historically provides the best results. There’s evidence that our ancestors ate 100-150 g/day—that’s a LOT of fiber! But for modern people, 35-50 grams a day is a great target number to discover the health benefits of this important nutrient.