Does prune juice relieve constipation?

Prune juice relieves constipation, according to SFGate. However, it does not work as effectively as whole prunes because it does not contain as much fiber. The human body doesn't digest fiber, and insoluble fiber softens and adds bulk to the stool.

The sorbitol found in prune juice also softens stools and allows them to pass more rapidly, says SFGate. Sorbitol is a type of partially digested sugar, or sugar alcohol. It passes more slowly into the bloodstream than the simple sugar glucose and has more time to absorb water from the lower gastrointestinal tract.

People who wish to increase their intake of prune juice should do so little by little to avoid the side effects of gas and bloating, claims SFGate.