It was a baffling medical mystery. A 21-year-old woman showed up at her doctor's office after having suffered abdominal pains and severe diarrhea for eight months — and losing 25 pounds.
Another patient, a 46-year-old man, arrived at the hospital with similar complaints. He had lost nearly 50 pounds.
In both cases, which occurred in Germany, the symptoms could have pointed to a severe food intolerance, serious bowel problems or worse. But after a battery of medical tests and a complete medical history, doctors in Berlin finally unlocked the secret behind the massive weight loss in these patients.
Sugarless gum. And lots of it.
Specifically, an ingredient in sugar-free gum called sorbitol — used instead of sugar to make the gum sweet — turned out to be the key culprit in both cases. In a report published Thursday in the British Medical Journal, the German doctors said the female patient had chewed up to 16 sticks of sugarless gum per day, while the male patient consumed about 20 sticks daily.
But in addition to being used as a sweetener, the ingredient has other uses in the medical arena.
"Both our patients consumed large amounts of sorbitol, which belongs to the family of polyalcohol sugars, like mannitol and xylitol, some of which are regularly used as laxatives," the study authors write.
"We've known about the diarrhea effects of sorbitol for some time," said Dr. David Posner, chief of gastroenterology at Mercy Medical Center in Baltimore. "People, when they overuse it, will have trouble with diarrhea and will lose weight because they have a lot of diarrhea and lose a lot of nutrients."
"It's actually a pretty classical teaching pearl when it comes to gastroenterology," said Dr. Ramon E. Rivera, gastroenterologist at Ochsner Medical Center's digestive disease center in New Orleans, La.
He notes that the cases elegantly illustrate the need for a complete and thorough medical history.
"History will give you the diagnosis," he said. "So most of the information you need is in the history itself."
"No one would think about asking the patient, 'do you chew gum?' But in medicine you have to be a detective. History is everything."
That being said, Rivera adds that cases this extreme — in which malnutrition occurs — are relatively rare.
Chewing off the Pounds
The very property that makes sorbitol friendly for waistlines is actually the same characteristic that makes large quantities of it such a problem.
"What happens is that it creates an osmotic gradient; as it goes through the gastrointestinal tract, it's like a sponge that pulls water out of the intestinal walls," Rivera said. "So imagine a sponge going down the gastrointestinal tract and absorbing fluid as it goes along."
All of this excess fluid in the bowel leads to diarrhea, as well as the host of unfortunate abdominal effects that come along with it.
Rivera adds that whether or not an individual experiences such symptoms depends largely on the sensitivity of his or her digestive tract. This sensitivity varies widely from person to person, he says. So while one person may not experience gastrointestinal symptoms from chewing a few dozen sticks of sugarless gum per day, others might experience problems with that amount.
Coincidentally, at least one gum company in the past has touted its product as a weight loss aid.
A research study conducted by the Wrigley Science Institute and presented at the 2007 Annual Scientific Meeting of The Obesity Society found that chewing gum before an afternoon snack may contribute to a weight loss plan. The gum maker's researchers showed that the product helped reduce hunger, diminish cravings and promote fullness among individuals who limit their overall calorie intake.
But it is unlikely that the potentially unpleasant laxative effect of sorbitol is what the gum companies have in mind when it comes to dropping pounds.
A Special Threat for Diabetics?
Though cases as severe as the ones documented in the new report may be uncommon, some say the problems associated with sorbitol could be more widespread than currently believed.
And people who consume a large amount of foods with sugar substitutes — namely diabetics — may be at special risk.
"We see this problem frequently in people with diabetes," said Julie Schwartz, a registered dietitian at the Emory Bariatric Center in Atlanta. "If you really looked at these cases, you might find that there are more gastrointestinal problems linked to sorbitol than to other perceived problems."
For example, she says she recalls one case of a patient who was assumed to be lactose intolerant, as he experienced the same kind of abdominal pain and diarrhea associated with this condition after eating ice cream and yogurt.
"When we really dove into the problem, we found out that he was eating sugar-free ice cream and sugar-free yogurt, which had sorbitol," she said. "We switched him over to full-sugar versions of ice cream and yogurt, and he had no problems anymore."
The authors of the report write that in light of the increasing number of sugar-free products hitting the shelves, more prominent labeling detailing the possible health effects of too much sorbitol is needed — a suggestion with which Schwartz agrees.
"I would definitely think that consumers should be aware that this product could have side effects," she said.
"People reach for sugar-free gum because they think it is healthier, but maybe it's really not."