Fiber

About Fiber

Dietary fiber consists of carbohydrates and lignin that resist digestion in the small intestine and pass into the colon. Official intake recommendations exist, and average intake in many Western countries falls well short of them. Fiber is classified as soluble or insoluble. Soluble fiber, found in oats, barley, legumes and psyllium, forms a gel, slows glucose absorption, binds bile acids and so lowers LDL cholesterol, and is fermented by gut bacteria into short chain fatty acids such as butyrate, propionate and acetate. Butyrate is the main energy source for the cells lining the colon. Insoluble fiber, such as wheat bran and cellulose, adds bulk to stool and helps prevent constipation. Fibers that feed beneficial gut microbes are also called prebiotics. High fiber diets are associated in observational studies with lower rates of cardiovascular disease, type 2 diabetes, colorectal cancer and overall mortality. A sudden large increase in fiber commonly causes temporary bloating and gas while the gut microbiota adapts.