September 15, 2026, 11:46 am | Read time: 5 minutes
When it comes to gut health, the discussion often centers around the microbiome. Probiotics from the drugstore are supposed to provide the “good” gut bacteria. But they are only part of the whole. For them to have any positive effects, an intact gut barrier is needed. FITBOOK Editor-in-Chief Nuno Alves spoke with gastroenterologist and author Prof. Dr. Martin Storr about the importance of this previously underestimated factor.
Not Only Gut Bacteria Keep the Gut Healthy
Researchers link changes in the gut microbiome–the entirety of bacteria living in the gut–to numerous health aspects, from metabolic diseases to chronic intestinal diseases and the gut-brain axis. Accordingly, there is great interest in probiotics, gut cleanses, and microbiome tests. However, despite high research activity, not all questions are answered: There is currently no scientifically recognized definition of an “optimal” gut microbiome. While certain bacterial species can be associated with health characteristics, the composition of the microbiome alone does not yet allow reliable conclusions about its actual function. Therefore, commercial microbiome stool tests that aim to identify “good” and “bad” bacteria and derive individual dietary recommendations are viewed critically by experts.1
For gastroenterologist Prof. Dr. Martin Storr, microbiome research falls short. According to the physician, who has just published the book “Intestinal Mucosa–The Unknown Superpower”, the mucous layer is increasingly coming into focus in science, having received relatively little attention in the “strongly microbiome-focused discussion.”
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Intestinal Mucosa and Microbiome Work as a Team
The gut faces a daily challenge: It must absorb nutrients from food while fending off potentially harmful substances and pathogens. This is ensured by the so-called gut barrier. It includes the microbiome, the intestinal mucosa, and parts of the immune system. There is a close exchange between these components. “The intestinal mucosa and the gut microbiome form a closely coordinated ecosystem,” explains Storr. The mucosa provides a habitat for microorganisms and produces mucus and antimicrobial substances. Conversely, many gut bacteria produce metabolic products that support the mucosa. Butyrate plays an important role in this. This short-chain fatty acid is produced when gut bacteria process fiber and serves, according to Storr, “as an energy source for the mucosal cells.”
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Gut Helpers: How Useful Are Probiotics and L-Glutamine?
Supplements for gut health often contain prebiotics (“food” for gut bacteria), probiotics (live bacteria), or L-glutamine. However, not everything marketed as a gut helper is well-supported by science. Storr especially advises differentiation with probiotics. Despite numerous studies, the scientific evidence for their effectiveness, such as in irritable bowel complaints, remains limited. The effect is “always strain-specific and also depends on the individual microbiome and the respective situation,” explains the gastroenterologist. Therefore, one cannot claim: “The more microbes or probiotics, the better.” A diverse and stable microbiome that is in balance with the intestinal mucosa is crucial for gut health.
Researchers currently have high hopes for so-called postbiotics. These are metabolic products or fermentates of microorganisms that are directly available to the gut. According to Storr, they are considered a “promising new approach to specifically support the gut barrier” and are increasingly becoming the focus of research.
L-glutamine is also often promoted as support for the gut barrier. While the amino acid serves as an important energy supplier for the cells of the intestinal mucosa, Storr’s assessment is cautious: “In certain severe diseases or after major surgeries, glutamine can be useful.” At the same time, he emphasizes: “For people with irritable bowel syndrome, digestive complaints, or for healthy individuals with supposedly ‘leaky gut,’ the benefit is not yet clearly proven.” According to the expert, the existing data is insufficient to make a general recommendation.
The expert therefore advises against viewing individual supplements as miracle cures. L-glutamine can at best be “a possible building block to support gut health.”
The Most Important Tips for a Healthy Gut
To protect your gut barrier, Storr suggests first having persistent complaints medically clarified. Digestive problems can be caused by conditions such as celiac disease or chronic inflammatory bowel diseases, which need targeted treatment.
If serious causes are ruled out, lifestyle plays an important role. Storr recommends a varied, fiber-rich diet with vegetables, legumes, whole grains, and other plant-based foods. This promotes a diverse microbiome and simultaneously supports the function of the gut barrier. Additionally, the gastroenterologist cites regular exercise, sufficient sleep, and good stress management as important components for gut health. Alcohol and nicotine should also be consumed in moderation.
For those considering dietary supplements, prebiotics are preferable to probiotics. Moreover, there are promising initial research results for the relatively new postbiotics. Reassuring to know: “The gut barrier has a remarkable ability to regenerate when the right conditions are created.”
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