How does sorbitol, a natural sugar alcohol in prunes, exert its laxative effect in the digestive system?

It draws water into the large intestine.

Sorbitol is classified as a sugar alcohol, and its physiological impact in the large intestine is primarily osmotic. The key characteristic that enables its laxative function is that the human body poorly absorbs sorbitol during digestion. Because this compound passes through the small intestine largely intact, it enters the large intestine where it exerts an osmotic pull. This means the sorbitol molecules attract and draw substantial amounts of water from the surrounding bodily fluids into the lumen of the large intestine. The increased presence of water lubricates the intestinal contents, significantly softening the stool mass and increasing its volume, which directly encourages colon contractions and promotes the desired laxative effect.