The goal of this clinical trial is to evaluate whether a synbiotic dietary supplement containing botanical extracts and multiple probiotic strains can improve gastrointestinal symptoms and modulate gut microbiota composition in adults diagnosed with Irritable Bowel Syndrome (IBS).

The main questions it aims to answer are:

Does supplementation with the synbiotic product improve functional gastrointestinal symptoms associated with IBS (e.g., bloating, abdominal discomfort, and bowel habit disturbances)?

Does the intervention lead to measurable changes in gut microbiota composition and selected biological markers compared with baseline measurements?

Participants will:

undergo baseline evaluation including symptom assessment, blood tests, and stool sample collection for gut microbiota analysis;

complete an 8-week observation period without intervention to establish baseline variability;

take the synbiotic supplement once daily for 8 weeks;

repeat clinical assessments, blood tests, and gut microbiota analysis during follow-up visits.

The human gut microbiota represents a complex ecosystem composed of trillions of microorganisms that play a fundamental role in maintaining host health. These microorganisms contribute to digestion, nutrient metabolism, immune modulation, and the maintenance of intestinal barrier integrity. Alterations in the composition and diversity of the gut microbiota, commonly referred to as dysbiosis, have been associated with a wide range of metabolic, inflammatory, and gastrointestinal disorders.

Among these conditions, Irritable Bowel Syndrome (IBS) is one of the most prevalent functional gastrointestinal disorders worldwide. IBS is characterized by chronic or recurrent abdominal pain, bloating, gas, and alterations in bowel habits, including constipation, diarrhea, or alternating patterns. Although the exact pathophysiology of IBS remains incompletely understood, increasing evidence suggests that alterations in gut microbiota composition and intestinal barrier function play an important role in symptom development and persistence.

Recent research has explored the use of probiotics and synbiotics as potential strategies to modulate gut microbiota and improve gastrointestinal symptoms. Probiotics are live microorganisms that, when administered in adequate amounts, may confer health benefits to the host by restoring microbial balance, enhancing mucosal barrier function, and modulating immune responses. Synbiotics combine probiotics with compounds that support their activity, such as prebiotic substrates or bioactive plant components.

In addition to probiotics, several plant-derived compounds have been investigated for their potential effects on gut microbiota and intestinal health. Botanical extracts rich in polyphenols and other bioactive compounds may exert antioxidant, anti-inflammatory, and prebiotic-like effects, supporting beneficial microbial populations and contributing to improved intestinal homeostasis. Nutritional cofactors, such as magnesium and vitamin B1, have also been linked to gut microbial metabolism and intestinal barrier function. Moreover, L-theanine, a bioactive compound derived from green tea leaves, has been studied for its potential role in modulating gut microbiota and immune responses.

The investigational product used in this study, TERRANOVA Microbiome Challenge, is a synbiotic dietary supplement that combines multiple probiotic strains with a botanical matrix and nutritional cofactors. The formulation includes probiotic strains such as Bacillus coagulans, Bifidobacterium bifidum, Lactocaseibacillus rhamnosus, and Lactiplantibacillus plantarum. The botanical matrix contains extracts from Cynara scolymus (artichoke leaf), Zingiber officinale (ginger root), Vaccinium myrtillus (bilberry), Matricaria recutita (chamomile flower), and Melissa officinalis (lemon balm leaf). The formulation also contains magnesium, vitamin B1, and L-theanine.

While individual components of this formulation have been investigated in preclinical and clinical studies, the combined effects of this specific synbiotic formulation on gut microbiota composition and IBS-related symptoms have not yet been evaluated in a clinical setting. Therefore, this study aims to explore the potential effects of this synbiotic supplement on gastrointestinal symptoms, biological markers, and gut microbiota composition in adults diagnosed with IBS.

This study is designed as a pilot, prospective, longitudinal clinical study with an intra-subject before-after design. A small exploratory sample of adult participants diagnosed with IBS will be included. The study will evaluate changes in symptoms, biological parameters, and gut microbiota over time within the same individuals.

The study will be conducted in three main phases over a total duration of approximately 16 weeks per participant.

During the first visit (baseline, T0), participants will undergo an initial clinical evaluation and complete standardized questionnaires assessing gastrointestinal symptoms. Blood samples will be collected to evaluate safety parameters, including hepatic, renal, inflammatory, and hematological markers. Stool samples will also be collected for gut microbiota analysis using 16S rRNA sequencing techniques.

The first phase of the study will consist of an observation period lasting eight weeks without the investigational intervention. This phase aims to establish a reference period and to reduce the influence of spontaneous symptom variability commonly observed in IBS. At the end of this observation period (T1), participants will undergo a second evaluation including symptom assessment, blood tests, and stool sample collection.

Following this period, participants will enter the intervention phase. During this phase, participants will receive the investigational synbiotic supplement for eight weeks. The supplement will be administered orally at a dose of one capsule per day, preferably after a meal, according to the manufacturer's recommendations.

Participants will be instructed to maintain their usual diet and lifestyle during the study and to avoid the use of additional probiotic or prebiotic supplements that could influence gut microbiota composition.

At the final visit (Tfinal), which takes place after completion of the eight-week supplementation period, participants will again undergo clinical evaluation, symptom assessment, blood testing, and gut microbiota analysis.

The primary objective of this study is to evaluate changes in gastrointestinal symptoms associated with IBS between baseline and the end of the study using standardized symptom assessment tools.

Secondary objectives include evaluating changes in selected biological markers, assessing changes in gut microbiota composition over time, exploring potential relationships between symptom changes and microbiota alterations, and evaluating adherence and tolerability of the intervention.

Safety monitoring will be conducted throughout the study. Participants will be asked to report any adverse events or changes in health status. Known potential side effects associated with probiotic supplementation, such as mild gastrointestinal discomfort, bloating, or changes in stool consistency, will be monitored. Any adverse events will be documented and evaluated by the research team.

The study will be conducted in accordance with the principles of the Declaration of Helsinki and applicable national regulations governing biomedical research involving human participants. Participation in the study will be voluntary, and all participants will provide written informed consent prior to enrollment. Participant confidentiality will be ensured through the use of coded identifiers and secure data storage procedures.

Due to the exploratory nature of this pilot study and the small sample size, statistical analyses will primarily be descriptive and exploratory. Comparisons will focus on intra-individual changes across the different study time points. The findings of this study are expected to provide preliminary insights into the potential role of synbiotic supplementation in the modulation of gut microbiota and symptom management in individuals with IBS, and may inform the design of larger controlled clinical trials in the future.

Inclusion Criteria:

• Adults aged ≥18 years
• Clinically confirmed diagnosis of Irritable Bowel Syndrome documented in the medical record
• Presence of recurrent gastrointestinal symptoms such as bloating, abdominal discomfort, gas, or bowel habit disturbances (constipation, diarrhea, or mixed pattern) considered clinically relevant by the participant
• Ability to understand the study procedures and provide written informed consent
• Willingness to participate for the full duration of the study (approximately 16 weeks) and attend study visits (T0, T1, and Tfinal)
• Willingness to provide biological samples (blood and stool samples for microbiota analysis) according to the study protocol

Exclusion Criteria:

• Known or suspected organic gastrointestinal disease explaining the symptoms (e.g., inflammatory bowel disease, untreated celiac disease, gastrointestinal malignancy)
• Presence of alarm symptoms such as unexplained gastrointestinal bleeding, significant unintentional weight loss, persistent fever, severe anemia, or signs of acute infection
• Acute gastrointestinal infection at the time of screening
• Use of antibiotics within the previous 4-8 weeks prior to baseline
• Use of probiotic, prebiotic, or microbiota-modifying supplements within 4 weeks prior to baseline that cannot be discontinued
• Planned major dietary changes or initiation of new treatments for gastrointestinal symptoms during the study period
• Pregnancy or breastfeeding
• Known allergy or hypersensitivity to any component of the investigational supplement
• Any severe comorbid condition or circumstance that, in the opinion of the investigator, could increase risk to the participant or interfere with study results

De-identified individual participant data (IPD) that underlie the results reported in the publication will be made available to qualified researchers upon reasonable request to the principal investigator. Data will be shared after publication of the study results, provided that the proposed use of the data is scientifically sound and approved by the study investigators, in accordance with applicable ethical and data protection regulations.

Individual participant data will be available beginning 6 months after publication of the primary study results and will remain available for up to 5 years.

Access to de-identified and fully anonymized individual participant data will be granted to qualified researchers who provide a methodologically sound research proposal. Requests for data should be submitted upon request to the principal investigator or the corresponding author of the study publication. Only anonymized data will be shared following approval of the research proposal and in accordance with applicable ethical and data protection regulations.