The following article is copyright by Ellen Coleman. By Ellen Coleman, RD, MA, MPH Dietary fibers are the portions of plants that cannot be digested by the human digestive tract. Soluble fiber delays gastric emptying and intestinal transit. Viscous soluble fiber sources also slow the appearance of glucose in the blood and decrease serum cholesterol .
Insoluble fibers speed up intestinal transit and increase stool weight.
They promote laxation and are either slowly or not fermented. However, insoluble fibers have no effect on serum cholesterol. Major food sources of insoluble fiber include wheat bran, whole grain products, and vegetables. Fruits, vegetables, and barley are sources of both insoluble and soluble fiber. Nearly all fiber containing foods have more insoluble than soluble dietary fiber.