Plums, and their dried form, prunes, are regarded as beneficial fruits often consumed as a natural remedy to promote regular bowel movements. While they offer advantages, consuming larger quantities can cause significant digestive changes, including loose stools or diarrhea. Understanding the specific components within plums that drive these effects is important for enjoying their benefits without discomfort.
Identifying the Key Components
Plums and prunes can cause diarrhea, especially when eaten in excess. This effect is due to the combined action of two naturally occurring substances within the fruit. The first is sorbitol, a sugar alcohol that the body poorly absorbs in the small intestine. The second substance is dietary fiber, which both fresh and dried plums contain in substantial amounts. These two compounds work through different physiological mechanisms to influence the consistency and frequency of bowel movements. Prunes, being dried, contain a far more concentrated amount of both sorbitol and fiber compared to fresh plums, which is why they are strongly associated with a laxative effect.
Sorbitol’s Osmotic Mechanism
Sorbitol is the primary driver of liquid stools associated with overconsumption. As a sugar alcohol, sorbitol is a small, osmotically-active molecule that is absorbed slowly and inefficiently by the small intestine. When large amounts are consumed, the unabsorbed portion travels onward to the large intestine. The high concentration of this solute in the colon creates an osmotic gradient, actively drawing water from the body’s tissues into the intestinal lumen. This influx of water significantly increases the fluid volume within the colon. The body eliminates this excess liquid, resulting in stools that are loose and watery, a condition known as osmotic diarrhea. In adults, consuming more than 20 grams of sorbitol per day is often enough to trigger these gastrointestinal symptoms.
How Fiber Impacts Gut Motility
Dietary fiber works alongside sorbitol to influence bowel function. Plums and prunes contain a mixture of both soluble and insoluble fiber. Insoluble fiber acts as a bulking agent, adding mass to the stool and helping it move more quickly through the digestive tract. By increasing the physical size of the stool, insoluble fiber accelerates gut motility, which is the speed at which waste travels through the intestines. Soluble fiber absorbs water in the gut, forming a gel-like substance that can both soften the stool. The overall high fiber content increases the total fecal volume, which triggers the muscles in the colon to contract more frequently and forcefully. This enhanced muscular action, or peristalsis, pushes the contents rapidly toward elimination.
Practical Advice for Safe Consumption
Because the components that cause digestive changes are concentrated in dried plums, moderation is the best strategy for avoiding diarrhea. A typical serving of five to six prunes contains about six grams of sorbitol. Limiting consumption to this small serving size per day helps keep the sorbitol intake below the threshold that commonly causes severe osmotic diarrhea. Fresh plums contain significantly less sorbitol and are less likely to cause issues unless a very large quantity is consumed. It is advisable to introduce prunes into the diet gradually, starting with just one or two per day, to allow the digestive system time to adjust to the increased fiber and sorbitol load. Individuals with pre-existing digestive conditions, such as Irritable Bowel Syndrome (IBS), should exercise caution. Sorbitol is classified as a FODMAP compound, and people with IBS are often highly sensitive to it. Always ensure adequate hydration when increasing fiber intake, as water helps the fiber move smoothly through the digestive system.