Irritable bowel syndrome (IBS) is a common disorder of gut–brain interaction, with a multifactorial pathophysiology involving gut–brain axis dysregulation, visceral hypersensitivity, microbiota imbalance, and immune dysfunction. Traditional IBS management emphasizes dietary modifications and pharmacologic therapies. However, increasing attention has been directed toward functional foods, nutraceuticals, and herbal remedies due to their potential to target IBS pathophysiological mechanisms with favorable safety profiles. This clinical review explores the role of these adjunctive therapies, evaluating evidence from preclinical and clinical studies. Functional foods such as kiwifruit, prunes, and rye bread demonstrate benefits in bowel habit regulation through fiber content and microbiota modulation. Nutraceuticals like peppermint oil, palmitoylethanolamide, and herbal mixtures exhibit anti-inflammatory, antispasmodic, and analgesic effects. Prebiotics provide substrate-driven microbiota changes, although dosage is key, as given their fermentative properties, when used at high dosages, they can exacerbate symptoms in some individuals. Probiotics and postbiotics offer microbiota-based interventions with promising symptom relief in IBS subtypes, although factors for personalized treatment still need to be further elucidated. These strategies highlight a paradigm shift in IBS management, integrating diet-based therapies with evolving nutraceutical options to improve patient outcomes. Despite promising findings, challenges in standardizing definitions, mechanisms, and safety profiles still remain. Rigorous, large-scale trials to validate the therapeutic potential of these interventions are needed, to enhance the benefits of these compounds with an individualized treatment approach.

Next-generation sequencing has overturned the dogma of biliary sterility, revealing low-biomass microbiota along the gut–biliary axis with metabolic and immunologic effects. This review synthesizes evidence on composition, function, and routes of colonization across benign and malignant disease. In cholelithiasis, Proteobacteria- and Firmicutes-rich consortia provide β-glucuronidase, phospholipase A₂, and bile salt hydrolase, driving bile supersaturation, nucleation, and recurrence. In primary sclerosing cholangitis, primary biliary cholangitis, and autoimmune hepatitis, intestinal dysbiosis and disturbed bile acid pools modulate pattern recognition receptors and bile acid signaling (FXR, TGR5), promote Th17 skewing, and injure cholangiocytes; bile frequently shows Enterococcus expansion linked to taurolithocholic acid. Distinct oncobiomes characterize cholangiocarcinoma subtypes; colibactin-positive Escherichia coli and intratumoral Gammaproteobacteria contribute to DNA damage and chemoresistance. In hepatocellular carcinoma, intratumoral microbial signatures correlate with tumor biology and prognosis. We critically appraise key methodological constraints—sampling route and post-sphincterotomy contamination, antibiotic prophylaxis, low biomass, and heterogeneous analytical pipelines—and outline a translational agenda: validated microbial/metabolomic biomarkers from bile, tissue, and stent biofilms; targeted modulation with selective antibiotics, engineered probiotics, fecal microbiota transplantation, and bile acid receptor modulators. Standardized protocols and spatial, multi-omic prospective studies are required to enable risk stratification and microbiota-informed therapeutics.

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by recurrent abdominal pain and altered bowel habits that significantly impair patients’ quality of life. Dietary triggers of IBS symptoms are common, and consequently, diet-based treatments are often prescribed. We conducted a review of current evidence on dietary interventions for IBS, focusing specifically on the evaluation of the scientific rationale and effectiveness of the most commonly adopted diets. Clinical trials and guideline recommendations were analyzed to assess each diet’s efficacy in symptom relief and patient adherence. Traditional dietary advice, although not a structured diet, but rather a set of lifestyle and dietary recommendations, is commonly recommended as first-line therapy and provides a solid base for symptom improvement in almost half of patients with IBS. Conversely, the low-FODMAP diet is a strict dietary pattern characterized first by the exclusion and then by the gradual and personalized reintroduction of several foods. Several clinical trials have demonstrated the efficacy of a low-FODMAP diet in reducing global IBS symptoms, and due to the established evidence, it is now incorporated into many clinical guidelines as a second- or even first-line approach for patients with IBS. Limited data supports the starch- and sucrose-reduced diet as an option for symptom relief, with evidence stemming from the relatively recent finding of hypomorphic variants of the sucrose-isomaltase gene in a subset of patients with IBS. Nonetheless, its application in clinical practice is still very limited. Data on gluten-free diet is more controversial as although it may benefit a subset of patients with IBS, strong evidence is still lacking for identifying the best candidates for a restrictive diet with a high burden in terms of economical, psychological and social costs. Beyond exclusion diets, a few studies on the Mediterranean diet suggest it may be a potential option with benefits that go beyond IBS symptom relief. Overall, dietary modification can significantly alleviate IBS symptoms. Tailoring recommendations to individual patient triggers may further enhance outcomes.