International Business Department           Liu Bojia           Feburary 19, 2023

  In the daily drink or eat some low-sugar, "0 sugar" snacks, if you have carefully read the list of ingredients, you may find that there are similar to erythritol, sucralose ingredients, in addition to sorbitol is also one of the common additives, these ingredients can provide sweetness at the same time does not provide, or very little to provide calories, is a sugar! The alternative to white granulated sugar.

  However, while sweeteners may help reduce calorie intake, the relationship between them and human health remains unclear. In recent years, studies have gradually revealed that sweeteners are not as safe as previously thought. For example, excessive intake of erythritol has been associated with accelerated thrombosis and elevated risk of cardiovascular disease, while high doses of sucralose can reduce immune cell activity and lower an individual's immune response to pathogens.

  In the latest Cell study, scientists from the University of California, Davis, also revealed the negative effects of sorbitol: when gut microbes change, individuals may not be able to process sorbitol, leading to symptoms of intolerance such as bloating and diarrhoea.

  Sorbitol is a polyol compound that occurs naturally in some fruits such as apples, pears and apricots, while it is also added to many candies, chocolates and beverages. Some past studies have found that the tolerance of sorbitol varies among different groups of people, with gastrointestinal discomfort occurring in healthy people when 20 grams of sorbitol is consumed, and no adverse effects when less than 5 grams is consumed. However, for patients with irritable bowel syndrome and inflammatory bowel disease, the consumption of 3-5 grams of sorbitol will increase gastrointestinal symptoms. In addition, if antibiotics are used along with sorbitol ingestion it can also cause symptoms such as diarrhoea, suggesting a potential link between microbes and sorbitol metabolism.

  To unravel the mechanisms behind this phenomenon, the researchers tested conditions affecting sorbitol metabolism in mice, first looking at the fact that antibiotics cause acute sorbitol intolerance, and that supplementation of sorbitol alongside antibiotic treatment led to an increase in faecal water content and a rapid loss of body weight in the mice. However, when the antibiotic treatment is stopped and the gut microbiome is restored, the mice's tolerance to sorbitol increases again.

  However, the recovery of the gut microbiome is significantly slowed down if the mice are on a high-fat diet for a long period of time. In the experiment, the authors also confirmed that antibiotics plus a high-fat diet can keep mice in a state of sorbitol intolerance for a long period of time, and that symptoms of intestinal discomfort occur whenever sorbitol is ingested.

  The sorbitol intolerance shown in the experiments was all linked to a gut microbe called Clostridium difficile, which produces enzymes that break down sorbitol, helping to reduce the burden of sorbitol on the gut.

  Since this type of bacteria is anaerobic, it prefers an environment with low oxygen levels. Antibiotics and a high-fat diet reduce oxygen consumption by gut cells, which can lead to more oxygen in the gut and inhibit the growth of Clostridium difficile, which can lead to a build-up of sorbitol.

  The study attempted to feed mice butyrate-producing bacteria, which increase oxygen metabolism in the gut cells as it ferments in the gut, thus decreasing oxygen levels in the gut. This move not only increased the number of Clostridium difficile bacteria, but also boosted the mice's tolerance to sorbitol.

  The authors note that this finding re-emphasises the importance of gut microbial balance for the metabolism of sugar and related molecules, and that we need to be more cautious about some foods containing sorbitol, especially some ketogenic weight loss diets that are higher in fat.