Do prunes make you poop?
Yes. The legend checks out. Prunes carry a sugar alcohol called sorbitol that pulls water into your gut, plus a good dose of fiber. In a head-to-head trial they beat a fiber supplement.
Did prunes make you go?
The meter says what should happen. Your bowels get a vote too.
Why it works
Sorbitol pulls water in
Your body only absorbs some of the sorbitol in prunes. The rest stays in the bowel and holds water there, which softens stool. A 50 g handful has about 7 g.
Fiber on top
The same handful adds about 3.6 g of fiber, which bulks stool up and helps the water stay put.
They beat psyllium in a trial
In a 3-week trial of 40 constipated adults, 50 g of prunes twice a day took complete bowel movements from about 1.7 to 3.5 a week, against 2.8 on psyllium. Prune growers funded the study.
Sources: Attaluri et al., Aliment Pharmacol Ther 2011; AAFP summary of the trial; USDA FoodData Central.