People should avoid sugar as much as possible, and those aware of the dangers may turn to alternative sweeteners. However, even alternative sweeteners should be met with caution when consuming.
Sorbitol is found naturally and in small amounts in apricots, apples, pears, avocadoes and other food, and is an alcohol sugar manufactured for sugar-free gum, mints, toothpaste, mouthwash, ice cream, candy and other products. Pregnant and breastfeeding women should steer away from it completely.
What is sorbitol?
At high levels, sorbitol can cause diarrhea and other side effects. Some studies have also implicated it in liver cancer and diabetic neuropathy. For many people, even a small amount of the chemical causes digestive upset, a condition known as “sorbitol intolerance.”
Scientists have not understood what causes this condition, but now, researchers at the University of California at Davis have identified changes in the gut microbiome that can result in an inability to digest. Their mouse study revealed that taking antibiotics, combined with a high-fat diet, reduced the number of Clostridia gut microbes, which can break down sorbitol. The findings have just been published in the journal Cell under the title “High fat intake sustains sorbitol intolerance after antibiotic-mediated Clostridia depletion from the gut microbiota."
“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,” said Jee-Yon Lee, one of the authors of the study and assistant project scientist in the UC Davis medical microbiology and immunology department.
How the researchers tested the experiment
The researchers used metagenomic analysis to identify which gut bacteria have genes that make the enzyme that breaks down sorbitol. This technique refers to the study of the structure and function of entire sequences isolated and analyzed from microbes in a bulk sample. They also identified which of those gut bacteria were plentiful before – but not after – treatment with an antibiotic.
This analysis allowed them to zero in on gut microbes belonging to the class Clostridium that don’t like environments containing oxygen.
The researchers found that after the mice were given antibiotics and fed a diet high in saturated fat, the cells lining the gut used less oxygen. This created a higher level of oxygen in the gut, decreasing Clostridia. Without enough Clostridia, sorbitol was not broken down in the gut. The team performed several experiments to try to restore the gut bacteria so it could break down sorbitol again.
In one, they fed the mice Anaerostipes caccae, a gut bacterium that produces butyrate – a short-chain fatty acid produced as part of the normal fermentation process in the gut. It enhances oxygen usage by the cells that line the gut, the epithelial lining, which reduces oxygen levels in the large intestine.
Regulating the oxygen level with Anaerostipes caccae restored the normal levels of Clostridia, which protected the mice from sorbitol-induced diarrhea, even after the butyrate-producing bacteria had been cleared from the mouse’s digestive system.
Future potential
The researchers suggest that a drug used to treat ulcerative colitis, Crohn’s disease, and other inflammatory bowel diseases, mesalazine (5-aminosalicylate), may be a treatment for sorbitol intolerance in humans. Mesalazine, also known as mesalamine, functions similarly to butyrate-producing bacteria, restoring the low oxygen levels in the intestine preferred by Clostridia.
“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.”
An important limitation of the study is that mice can tolerate much higher sorbitol levels than humans. Mice possess a cecum – a pouch in their digestive system that slows the flow of intestinal contents and helps digest carbohydrates that may contribute to being able to better tolerate sorbitol. Clinical studies will be needed to test the hypothesis that mesalazine could treat sorbitol intolerance in humans.
“Our study provides a completely new starting point for approaches to diagnose, prevent, and treat sorbitol intolerance,” said Prof. Andreas Bäumler, a senior author of the study.