Why Sugar-Free Gum Gives You Gas

Sugar-free gum might be good for your teeth, but not so much for your guts, as scientists have found why it can trigger gas in some people.

One of the ingredients of sugar-free gum, sorbitol, can cause digestive cramps, bloating, and diarrhea in high concentrations, but for some people, these symptoms can arise after only a small dose, due to them having sorbitol intolerance.

Now, scientists have found that a high-fat diet combined with taking antibiotics can trigger this sorbitol intolerance in mice, according to a new paper in the journal Cell.

Sorbitol is a sugar alcohol used in sugar-free candies and mints, and is naturally found in various fruits, including apricots, apples, pears and avocados.

Usually, sorbitol is broken down in the gut, with only high doses of sorbitol causing issues. However, if sorbitol cannot be broken down, then it passes through the small intestine to the colon where other species of bacteria break it down through fermentation. This fermentation process results in the production of gas, leading to bloating and even diarrhea.

The researchers used metagenomic analysis to figure out that Clostridia gut microbes were responsible for breaking down sorbitol normally, and were absent in those with sorbitol intolerance. They also found that taking antibiotics and eating a high-fat diet can reduce the number of Clostridia gut bacteria in mice, leading to sorbitol intolerance.

"Our research suggests that microbial sorbitol degradation normally protects the host against sorbitol intolerance. However, an impairment in the microbial ability to break down sorbitol causes sorbitol intolerance," paper co-author Jee-Yon Lee, an assistant project scientist in the UC Davis Department of Medical Microbiology and Immunology, said in a statement.

Clostridium bacteria are anaerobic, meaning that they thrive in environments without oxygen present and struggle in the presence of oxygen. The researchers found that if the mice were given antibiotics and ate a diet higher in fat, the cells lining the gut used up less oxygen, leaving more of it present in the gut space, and therefore exposing the bacteria to more oxygen. This prevented the bacteria from growing, meaning fewer were present to break down the sorbitol in the mice's guts.

"This discovery is crucial, given the prevalent use of sorbitol and similar sugar alcohols in the production of keto-friendly diet foods that are high in fat content," Lee said. "It also highlights the importance of oxygen consumption by the epithelial lining in the intestines in maintaining a healthy balance of gut bacteria, especially Clostridia, for proper digestion of certain sugars."

In the paper, the researchers explain that they investigated how they could restore the gut bacteria, including by feeding the mice a bacteria called Anaerostipes caccae that produced a chemical called butyrate, which enhances the oxygen use of the cells in the gut, and thus lowered the oxygen levels in the area where bacteria live. This restored the original level of Clostridia bacteria, subsequently protecting the mice from sorbitol intolerance, even after Anaerostipes caccae had been cleared from their guts.

"Our study provides a completely new starting point for approaches to diagnose, prevent and treat sorbitol intolerance," paper co-author Andreas Bäumler, a distinguished professor and vice chair of research in the UC Davis Department of Medical Microbiology and Immunology, said in the statement.

Of course, all of this is occurring in mice, which have much higher sorbitol tolerances than humans. This is because they have a special pouch in their digestive system known as a cecum, which helps them digest carbohydrates. More research needs to be done into how sorbitol intolerance works in humans, and how it can be treated.

In the paper, the researchers suggested that one solution to sorbitol intolerance in humans could be treated using a drug called mesalazine (5-aminosalicylate), which is usually used to fight ulcerative colitis, Crohn's disease and other inflammatory bowel diseases. This drug functions in a similar way to the butyrate-producing bacteria in the mice, restoring the low oxygen levels in the intestine in which Clostridia bacteria thrive.

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