The noble prune: a delicious, dried treat whose origin is the plum. Nobody really knows who dried the first plum, though the fruit’s origin may be found in the Aquitaine region of southwestern France. 
Recently, the U.S. officially changed the name of the prune to “dried plum,” as this new name not only describes the fruity delicacy to perfection, but also made it easier to market to those other than the elderly. Why the elderly? Because prunes and their juice have long been associated with having natural laxative qualities. Prune producers lobbied the U.S. Food and Drug Administration for the name change because they were tired of their product being inextricably tied to the notion of regular bathroom visits.
How Do Prunes Work?
Still, prunes and prune juice have been championed, especially by the elderly, as gentle and effective laxatives since at least the 1800s.
Prunes contain a great deal of the sugar sorbitol, which is one of the few sugars that does not ferment (and why plums are one of the few fruits that dry without rotting). In the gut, sorbitol helps produce an environment that favors friendly bacteria. Prunes, in their native state, also contain a lot of insoluble fiber, which helps to bring liquid to the intestines. These prune elements also tend to slow down the digestive system, allowing for better absorption of nutrients.
Additionally, dried plums contain many other beneficial compounds such as potassium, which is good for heart health, phenols (a class of antioxidant chemical compounds that seek out free radicals and can aid in cancer prevention), and a good amount of vitamin A, which helps to ensure good vision, skin, cellular health, and immune function. 
The question is: Is prune juice safe as a laxative meant for regular use? The simple answer is yes, though that comes with a few hiccups.
Potential Problems with Prunes and Prune Juice
In a study that included three people experiencing chronic diarrhea, the culprit was found to be eating prunes and drinking prune juice on a daily basis in two of the cases. Too much “pruning,” it seems, can be a bad thing.  Rather than consume prunes or prune juice every day, other options are available. Another study saw elderly residents at a geriatric center given a bran supplement to their regular hot cereal. This simple change helped to prevent constipation in 60 percent of residents who needed to use laxatives before, saving tens of thousands of dollars. 
Prune juice, being naturally high in sugar, would not be recommended for those with blood glucose problems. Once prunes are turned into juice, their sugar-concentrated content may prove deleterious to diabetics and those with hypoglycemia. The addition of such a high-sugar food could lead to blood-sugar level complications. Pregnant mothers, who sometimes suffer from gestational diabetes, also may be at risk, and it’s best for those affected to drink prune juice judiciously. However, prunes themselves don’t cause blood sugar concentration to go up quickly, making them relatively safe. This is hypothesized to be due to the high sorbitol, fructose, and fiber content. 
Other studies have shown that because prunes act luminally, any negative effects they have would be limited to the gastrointestinal tract. This is good news, unless you have a gastric disorder where periodic bowel control is already a problem. In that case, prune juice would not be a good choice for the relief of periodic constipation. People suffering from Irritable Bowel Syndrome, for example, might have their symptoms exacerbated by the intestinal water volume increase associated with this juice. 
For the rest of us, prunes and prune juice are natural, effective, gentle ways to keep the bowels moving – as long as you use them in moderation. It’s flavorful, high in a few key vitamins and minerals, easy to ingest, and, as an occasional laxative for those with healthy constitutions, works great.
-Dr. Edward F. Group III, DC, ND, DACBN, DABFM
- Stacewicz-Sapuntzakis M, Bowen PE, Hussain EA, Damayanti-Wood BI, Farnsworth NR. Chemical composition and potential health effects of prunes: a functional food? Crit Rev Food Sci Nutr. 2001 May;41(4):251-86. Review.
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- Menees S, Saad R, Chey WD. Agents that act luminally to treat diarrhoea and constipation. Nat Rev Gastroenterol Hepatol. 2012 Nov;9(11):661-74. doi: 10.1038/nrgastro.2012.162. Epub 2012 Sep 4. Review.