Dietary fibers can act by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed.[2] Some types of soluble fiber absorb water to become a gelatinous, viscous substance which is fermented by bacteria in the digestive tract. Some types of insoluble fiber have bulking action and are not fermented.[3] Lignin, a major dietary insoluble fiber source, may alter the rate and metabolism of soluble fibers.[1] Other types of insoluble fiber, notably resistant starch, are fully fermented.[4] Some but not all soluble plant fibers block intestinal mucosal adherence and translocation of potentially pathogenic bacteria and may therefore modulate intestinal inflammation, an effect that has been termed contrabiotic.[5][6]