Irritable Bowel Syndrome: The Latest Scientific Findings on the Microbiome and Probiotics

The information presented in the following Q&A is carefully selected and synthesized from the peer-reviewed scientific review “Exploring Gut Microbiota Imbalance in Irritable Bowel Syndrome: Potential Therapeutic Effects of Probiotics and Their Metabolites,” published in Nutrients in January 2025 (García Mansilla et al., 2025). The review was authored by a team of leading researchers and clinicians from several Spanish academic and biomedical institutions: the University of Granada, the Center for Biomedical Research (CIBM), the Institute for Biomedical Research (ibs.GRANADA), the Biomedical Research Institute of Málaga, and the National Nanomedicine Platform IBIMA. The authors—Dr. María José García Mansilla, Dr. María Jesús Rodríguez Sojo, Dr. Andrea Lista, Dr. Antonio Ruiz Malagón, and colleagues—are specialists in pharmacology, gastroenterology, microbiology, and molecular biology.

This selection aims to address five of the most practical and frequently asked questions by IBS patients, offering up-to-date, objective, and easy-to-understand scientific information drawn directly from the original research source.

“IBS symptoms aren’t just about sensitivity—behind them lies a complex interplay between the microbiome, the immune system, and the brain. New scientific insights are placing probiotics and gut-derived metabolites at the center of treatment strategies.”

Expert Opinions on IBS and the Role of Gut Microbiota

Irritable Bowel Syndrome (IBS) is one of the most common functional gastrointestinal disorders, affecting approximately 10% of the global population. Its main symptoms—recurring abdominal pain, bloating, gas, and changes in stool frequency or consistency—can severely impact quality of life, even though the condition is not life-threatening. Over the past decade, our understanding of IBS has evolved significantly: research now shows that, in addition to factors like stress, genetics, and diet, the state of the gut microbiota plays a key role. An imbalanced microbiome (known as “dysbiosis”) can affect not just gut function, but also brain-gut communication, immune responses, inflammation, and even mental health.

In this context, expert opinions—from doctors, scientists, microbiologists, and clinical researchers—are essential for helping patients and their families navigate modern approaches to managing and treating IBS. Below is a curated collection of expert insights and scientific excerpts addressing the core issues surrounding the condition.

1. What do we know about the causes and mechanisms of IBS? (Pathophysiology)

“The pathophysiology of IBS is complex and multifactorial, involving interactions between motor, sensory, microbiological, immunological, and psychological factors… Many studies suggest that the diversity, stability, and metabolic activity of the gut microbiota are often disrupted in IBS, leading to dysbiosis…”

“…It has been shown that immune activation in the colonic mucosa of IBS patients is accompanied by infiltration of immune cells and the release of pro-inflammatory cytokines, including IL-6, TNF-α, IL-17, and IL-1β… Increased intestinal permeability in IBS suggests a compromised epithelial barrier mechanism, which may lead to inflammation and abnormal immune responses.”

2. Is there evidence of a connection between the microbiome and mental health in IBS?

“A significant correlation has been identified between the gut microbiota of IBS patients and psychological conditions such as anxiety and depression… Studies involving human microbiota transplantation in mice support the role of gut bacteria not only in the pathogenesis of IBS but also in its psychological comorbidities…”

“Dysbiosis may impact the microbiota-gut-brain axis, and probiotics can help normalize this connection. Certain probiotic strains (e.g., Lactobacillus rhamnosus) reduce stress-induced corticosterone release by modulating GABA receptors linked to anxiety, thus decreasing the frequency and severity of abdominal pain in IBS patients.”

3. What probiotics are recommended, and how do they work?

“Probiotics can restore the balance and composition of gut microbiota and enhance the beneficial activities of microbial communities, leading to improvement or prevention of gut inflammation and other gastrointestinal disease phenotypes… Increasing levels of Lactobacillus and Bifidobacterium via probiotics restores and stabilizes an environment unfavorable to pathogens. Lactobacilli and other probiotics boost mucin secretion and regulate tight junction protein synthesis, limiting the entry of toxins and pathogens.”

“Among the most studied strains are Bifidobacterium lactis HN019, Bifidobacterium lactis DN-173 010, Bacillus coagulans, and multi-strain combinations of Lactobacillus and Bifidobacterium.”

4. What probiotic metabolites (postbiotics) matter, and why?

“Recent research shows that not only live probiotics but also their bioactive metabolites (known as postbiotics—SCFAs, vitamins, neurotransmitters) may be key in relieving IBS symptoms… For example, butyrate is a primary energy source for colon epithelial cells and strengthens the intestinal barrier, while propionate and acetate help regulate gut motility and inflammation… Postbiotics have potential as standalone therapeutic strategies without the risks associated with consuming live microorganisms.”

5. What role do vitamins (especially D, B6, B12) play in IBS and gut health?

“Vitamin D deficiency is present in up to 82% of IBS patients and is strongly correlated with impaired gut barrier function and increased inflammatory activity… Studies involving vitamin D supplementation have shown improvements in quality of life, anxiety, and symptoms in some patients. There is also evidence that probiotics may enhance vitamin D absorption.”

“Vitamin B12, beyond its role as a coenzyme in various metabolic processes, is synthesized by some gut bacteria and is important for maintaining bacterial diversity. Vitamin B6 is linked to inflammation, and low intake has been associated with more severe IBS symptoms.”

Q&A

1. Is IBS a disease that can be fully cured, and does it pose any life-threatening risks?

Answer: IBS is not a condition that increases the risk of death or leads to severe, life-threatening complications. However, its chronic nature can significantly disrupt quality of life and result in considerable financial and social burdens. Currently, there is no definitive or universal cure for IBS. Treatments mainly aim to relieve symptoms and improve the patient's overall well-being.

2. Why are IBS symptoms so different from person to person, and are there different types of IBS?

Answer: IBS symptoms vary widely because the condition has several subtypes based on the predominant symptom:

• IBS with predominant constipation (IBS-C)

• IBS with predominant diarrhea (IBS-D)

• Mixed-type IBS (IBS-M)

• Unclassified IBS

These differences are rooted in a complex interaction of genetic factors, microbiota, the immune system, stress, and even epigenetic changes. This makes treatment highly individualized and requires a tailored approach based on the specific subtype and patient characteristics.

3. Is there a link between diet and the onset or worsening of IBS symptoms?

Answer: Yes, dietary habits and specific food products can significantly impact IBS symptoms. The article highlights that food antigens and bacterial byproducts can activate immune cells in the gut lining, leading to inflammation, increased intestinal permeability, and symptom flare-ups. Additionally, certain dietary patterns (such as high animal-product intake or restrictive diets) can alter the gut microbiota composition and metabolic profile, which may also contribute to the manifestation or worsening of IBS symptoms.

4. Can probiotics or their metabolites be harmful, and are there risks to using them?

Answer: Although probiotics are generally considered safe and well-tolerated, the article notes that their effectiveness depends on many factors—including the specific strains used, dosage, and duration of intake. In certain patients and situations, the expected benefits may not occur, and side effects such as bloating or digestive discomfort may be experienced. It is important to use probiotics under medical guidance rather than randomly, especially in individuals with weakened immune systems or chronic illnesses.

5. How reliable are current diagnostic and treatment approaches for IBS, according to scientists?

Answer: IBS diagnosis is based on symptoms, the absence of alarming signs, and ruling out other conditions. There is currently no biomarker that can definitively confirm or rule out IBS. Treatment is multifaceted, including dietary changes, medications to manage motility and pain, psychotherapy, and—more recently—the use of probiotics and postbiotics. The article emphasizes the need for further research to determine optimal probiotic strains and dosages and whether different IBS subtypes require different therapies. Long-term effectiveness and safety are still under investigation, so all treatments should be personalized and discussed with a healthcare provider.

Conclusion

Understanding and managing Irritable Bowel Syndrome requires not just trust in your doctor but also familiarity with current science. As shown in the review by García Mansilla et al. (2025), knowledge about the role of gut microbiota, probiotics, and their metabolites in IBS pathogenesis and treatment is rapidly evolving. While there are still no final, one-size-fits-all solutions, patients now have access to increasingly personalized strategies and better tools to control their symptoms. It is strongly recommended that any decision involving dietary changes, probiotics, or other alternative treatments be discussed with a medical professional, as IBS research is dynamic and demands a balanced, individualized application of scientific discoveries for the patient’s benefit.

Source: 

García Mansilla, M.J., Rodríguez Sojo, M.J., Lista, A.R., Ayala Mosqueda, C.V., Ruiz Malagón, A.J., Gálvez, J., Rodríguez Nogales, A., Rodríguez Sánchez, M.J. Exploring Gut Microbiota Imbalance in Irritable Bowel Syndrome: Potential Therapeutic Effects of Probiotics and Their Metabolites. Nutrients 2025, 17, 155. 

https://doi.org/10.3390/nu17010155