Sorbitol

Discussion

Chronic diarrhea can result from myriad pathologies. The initial evaluation begins with a detailed history. In this case, although the patient believed the diarrhea was meal related, we determined that the diarrhea was occurring 4 to 6 hours after meals, and actually correlated with the time of chewing the gum, which she did several hours after her meals. Because she did not want to be disturbed to go to the bathroom at night, she developed a habit of having her last meal by 6 pm. Curiously, she also decided not to chew gum after that time, even though she had no sense that the gum was a factor.

This case had an unusual number of “red herrings.” She had traveled shortly before the diarrhea started. Blastocystis is occasionally thought to be pathogenic in humans and is treated in cases of diarrhea where no other cause is found. She also had a family history of both Crohn disease and colon cancer.

Sorbitol is a hexahydric sugar alcohol used commonly in the food industry as a sweetener and also to improve the texture and shelf-life of foods. Sorbitol is present in many chewing gums and other confections, in some processed foods, and naturally in some foods (apples, apricots, dates, figs, nectarines, peaches, pears, plums, prunes, and raisins). It is also added to some liquid medications as a sweetener.

One stick of Trident gum contains about 1.25 g of sorbitol, and there are 16 to 18 sticks per pack (20 to 22.5 g of sorbitol). Depending on the flavour and format of the Trident product, some also contain maltitol, xylitol, or mannitol, but in smaller amounts than the sorbitol. Sorbitol can cause gastrointestinal symptoms (gas, urgency, bloating, abdominal cramps) in a dose-dependent manner (5 to 20 g per day). Doses of more than 20 g per day can cause diarrhea, with at least 1 case report of associated weight loss.¹

These effects vary from one individual to another. In a metabolic laboratory, participants (N = 18) consumed a much higher dose than our patient did (40 g of sorbitol per day) and reported a change in the consistency of bowel movements to “loose” within 1 to 3 hours of ingestion.² Sorbitol increased both stool water content and total stool output per day compared with placebo. Of interest, the amount of participant-reported loose stool associated with sorbitol did not meet the definition of clinically relevant diarrhea (stool output of > 250 g per day and bowel movement frequency > 3 per day)³ during the study period.

There are several factors that can modulate the laxative effects of sorbitol. Concurrent ingestion of other foodstuffs can affect absorption. Sorbitol absorption was increased when it was administered with rice gruel (ie, extra glucose), suggesting that concurrent ingestion of glucose might reduce the osmotic diarrheal effect of sorbitol.⁴ A study in rats found that possible causes of sorbitol-associated diarrhea include faster intestinal transit, small-bowel malabsorption, incomplete colonic fermentation of sorbitol into short-chain fatty acids (possibly owing to variations in the microbiome), and slower absorption of breakdown products from the colon.⁴

A recent randomized controlled trial in postsurgical patients (N = 82) demonstrated that chewing gum decreased time to passage of first flatus, first bowel motion, and feelings of hunger.⁵ Patients had 1 piece of chewing gum 3 times daily. There were no complications in the chewing gum group. The dose of chewing gum was much lower than the dose known to cause diarrhea or even gastrointestinal side effects. We speculate that in this early postoperative population, who were not ingesting anything else, the lack of attenuating effects of co-ingested substances might have amplified the effects of the chewing gum even at this low dose.