Final answer:
Psyllium (Metamucil) is a bulk-forming laxative that works by absorbing water and increasing the bulk of feces, stimulating peristalsis in the large intestine to ease bowel movements. It is a type of soluble fiber that remains largely undigested, unlike stimulant laxatives or stool softeners.
Step-by-step explanation:
Psyllium, commonly known as Metamucil, is a form of soluble fiber derived from the husks of Plantago ovata seeds. It is classified as a bulk-forming laxative due to its water-absorbing properties, which increase the bulk and moisture content of stool. This action helps to stimulate peristalsis, the natural movement of the digestive tract that pushes waste through the large intestine. Unlike stimulant laxatives that increase intestinal motility through irritation of the intestinal lining, or stool softeners that allow water and fats to penetrate the stool, psyllium's mechanism of action is primarily through physically bulking up the fecal mass, enhancing regularity.
Moreover, psyllium is a nondigestible carbohydrate, and as it passes through the gastrointestinal tract, it remains largely unaffected by digestive enzymes. Because of its ability to absorb water and its resistance to digestion, it adds bulk to the feces, easing bowel movements. It also has the added benefit of potentially alleviating symptoms associated with irritable bowel syndrome (IBS) by modifying food choices, as part of an overall dietary management plan.