Here is a question from a faithful reader:
“Is plum juice as effective as prune juice as a laxative for elders? Your column is so reliable &appreciated. g.w.”
We might think this would be an easy question since we know that prunes are plums that have been dried … right? Yet according to the California Dried Plum Board, “all prunes are dried plums but not all plums are dried prunes.”
Plum varieties that become prunes, they explain, are higher in sugar content so they can be dried with their pits without fermenting.
Incidentally, “prunes” were renamed “dried plums” after research showed that we consumers are more inclined to purchase “dried plums” than “prunes.”
Prunes and prune juice get their laxative effect from naturally-occurring substances, including dietary fiber, half of which is “insoluble” fiber which helps movement through the digestive tract.
They also contain the mineral magnesium, a common ingredient in some laxative formulas.
Lastly dried prunes and prune juice are a natural source of sorbitol, a sugar alcohol known for its stool-loosening effect.
So what about plum juice? According to their Nutrition Facts labels, 1 cup of plum juice contains the same amount of dietary fiber — about 3 grams — as 1 cup of prune juice. And both juices contain similar amounts of magnesium and sugar.
Cup for cup however, prune juice is slightly higher in calories (180 vs. 160 calories in plum juice) and total carbohydrates, 42 grams vs, 36 grams in plum juice.
And although I could not confirm this with various sources out there in cyberspace, this could mean that prune juice is slightly higher in sorbitol, the sugar alcohol with a laxative effect.
Barbara Quinn is a registered dietitian and certified diabetes educator at the Community Hospital of the Monterey Peninsula. She appears in the new publication “What Doctors Eat,” Email her at bquinnchomp.org.