Dietary Fibres on Gut Fermentation

Acute Effects of Different Dietary Fibres on Gut Fermentation: A Pilot Study

The goal of this clinical trial is to learn if adding a rapidly fermenting fibre to a meal containing a slow fermenting fibre affects gut bacterial fermentation and digestive comfort in healthy adults aged 18 to 85 years. The main questions it aims to answer are:

• Does the addition of a fast fermenting fibre to a meal containing a slow fermenting fibre change the timing and amount of gas produced by gut bacterial fermentation?
• Does the addition of a fast fermenting fibre as a split dose effectively reduce the digestive discomfort typically caused by consuming a high dose of fibre all at once?

Researchers will compare the effect of adding fructo-oligosaccharides (FOS) over-and-above a single dietary fibre (soluble corn fibre). They will also compare whether taking FOS either all at once versus splitting it into two smaller doses affects gut bacterial fermentation and digestive comfort.

Participants will:

• Visit the research laboratory for 3 test days, with a 1-week break between visits.
• Avoid certain foods and fast overnight before each test day.
• Eat a test breakfast and lunch containing the dietary fibres in different parts of the meal.
• Provide breath samples every 30 minutes to measure gas produced by gut bacteria.
• Answer survey questions about their digestive comfort every 30 minutes.
• Keep a diary of their bowel movements for 5 days during each test cycle.

Short-chain fatty acids (SCFAs) produced through dietary fibre fermentation are essential for maintaining intestinal barrier integrity and regulating systemic metabolism; however, average daily fibre intake frequently remains below recommended levels. While supplementing with highly fermentable fibres, such as fructo-oligosaccharides (FOS), effectively stimulates beneficial microbial activity in the proximal colon, their rapid breakdown often triggers acute gastrointestinal discomfort, including bloating and flatulence. Conversely, soluble corn fibre (SCF) possesses a highly branched structure that ferments slowly and reaches the distal colon, exhibiting excellent gastrointestinal tolerability but yielding a lower initial peak of SCFA production.

Study Overview

• Status: Recruiting
• Conditions: Healthy Adult
• Intervention / Treatment: Dietary supplement: SCF Alone; Dietary supplement: SCF and FOS (Single Dose); Dietary supplement: SCF and FOS (Split Dose)

Detailed Description

This study aims to investigate the effect of rapidly fermenting FOS over-and-above slowly fermenting SCF and whether this supports a "spatio-temporal fermentation profile" spanning the entire colonic tract. By balancing fermentation speeds, this strategy holds the potential to maximise total colonic fermentation yield whilst mitigating the adverse symptoms typically associated with isolated high-dose FOS intake. Furthermore, the study explores a split-dosing regimen as an additional temporal strategy; dividing the FOS intake may limit the peak rate of gas production, preventing it from exceeding the gut's natural gas clearance mechanisms, while ensuring a sustained delivery of fermentable substrates.

To evaluate these physiological dynamics, healthy adult participants will complete a randomised, double-blind, crossover trial comprising three distinct acute testing days, separated by 7-day washout periods. Under strict dietary standardisation and overnight fasting conditions, participants will consume meals containing specific dietary fibres. The acute physiological responses will be continuously monitored via non-invasive breath hydrogen and methane analysis to objectively map fermentation kinetics, alongside regular self-reported assessments of gastrointestinal tolerability throughout the testing window.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Kuan-Yu Lin; Phone Number: +44 7799056885; Email: kyl205@bath.ac.uk

Study Locations

• United Kingdom
  • Somerset
    • Bath, Somerset, United Kingdom, BA2 7AY
      • Recruiting
      • University of Bath
      • Contact: Kuan-Yu Lin; Phone Number: +44 7799056885; Email: kyl205@bath.ac.uk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 85 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Healthy males and females, aged between 18 and 85 years at the start of the study.
• Self-reported regular bowel habits, defined as an average frequency of between 3 and 21 bowel movements per week (Mitsuhashi et al., 2018). This weekly average accounts for normal daily fluctuations while ensuring an overall healthy baseline.
• Willing and able to comply with all study protocols, including pre-test dietary restrictions (avoiding highly fermentable foods), a 12-hour overnight fast, and consumption of the prescribed dietary fibre test meals.
• Willing to accurately record gastrointestinal symptoms using the Visual Analogue Scale (VAS) and complete the Bristol Stool Scale (BSS) logs over the specified periods.
• Able to understand the study procedures and provide written informed consent.

Exclusion Criteria:

• History or current diagnosis of chronic gastrointestinal diseases or conditions (e.g., Irritable Bowel Syndrome [IBS], Inflammatory Bowel Disease [IBD], coeliac disease, chronic constipation, or history of major gastrointestinal surgery).
• Use of systemic antibiotics, prebiotics, probiotics, or medications known to significantly alter gastrointestinal motility within the 3 months prior to the commencement of, or during the study period.
• Known food allergies or severe intolerances to any ingredients present in the test meals (e.g., soluble corn fibre, fructo-oligosaccharides).
• Females who are currently pregnant, planning to become pregnant during the study period, or lactating.
• Currently following a highly restrictive or extreme diet (e.g., strict ketogenic, extreme high-fibre, or medically prescribed diets) that could significantly confound the baseline gut microbiota or fermentation profile.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: SCF Alone; Participants will consume a standardised breakfast containing SCF in the drink component. Three hours later, they will consume a standardised low-fibre lunch.	Dietary supplement: SCF Alone; Administration of SCF with breakfast.
Experimental: Single Combined Dose (SCF + FOS); Participants will consume a standardised breakfast containing SCF in the drink component. They will also consume a meal containing a full dose of FOS. Three hours later, they will consume a standardized low-fibre lunch.	Dietary supplement: SCF and FOS (Single Dose); Administration of FOS as a single dose over-and-above SCF with breakfast.
Experimental: Split-Dosed Combination (SCF + FOS); Participants will consume a standardised breakfast containing SCF in the drink component. They will also consume a meal containing half the dose of FOS. Three hours later, they will consume a standardized low-fibre lunch containing the other half of the dose of FOS.	Dietary supplement: SCF and FOS (Split Dose); Administration of FOS at breakfast and at lunch, over-and-above SCF at breakfast.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Area Under the Curve (AUC) of Breath Hydrogen and Methane Production	Total colonic fermentation yield is evaluated by measuring breath hydrogen and methane concentrations. Breath samples are collected at 30-minute intervals post-intervention using Omed breath analysers. The total production for both gases is quantified independently by calculating their respective AUC values from the averaged concentration-time profiles.	Baseline (fasting) and every 30 minutes up to 8 hours on each acute test day

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fermentation Kinetic Parameters: Maximum Peak Concentration (Cmax) of Breath Gases	The dynamic temporal characteristics of gut fermentation are evaluated by determining the maximum peak concentration (Cmax) for both breath hydrogen and methane. Data is extracted from continuous breath samples collected using Omed breath analysers.	Baseline (fasting) and every 30 minutes up to 8 hours on each acute test day.
Fermentation Kinetic Parameters: Time to Peak (Tmax) of Breath Gases	The dynamic temporal characteristics of gut fermentation are evaluated by determining the time required to reach this peak concentration (Tmax) for both breath hydrogen and methane. Data is extracted from continuous breath samples collected using Omed breath analysers.	Baseline (fasting) and every 30 minutes up to 8 hours on each acute test day.
Acute Gastrointestinal (GI) Tolerability Composite Score	The incidence and severity of subjective GI symptoms (bloating, abdominal cramping, stomach noises/borborygmi, and flatulence) are rated by participants on a scale from 0 (absent) to 10 (extremely severe). Any bowel movements are logged and converted into a stool score from 0 (normal transit) to 10 (diarrhoea). These are summed to calculate a total composite score ranging from 0 to 50, with higher scores indicating worse GI tolerability.	Baseline (fasting) and every 30 minutes up to 8 hours on each acute test day.
Lower Gastrointestinal Response Assessed by the Bristol Stool Scale (BSS)	Participants monitor and log their daily bowel movement frequency and utilise the Bristol Stool Scale (BSS) to objectively assess stool consistency and appearance. This tracks delayed lower gastrointestinal responses beyond the immediate acute testing window.	Baseline (fasting) and every 30 minutes up to 8 hours on each acute test day.

Collaborators and Investigators

• Sponsor: University of Bath
• Investigators: Principal Investigator: Dylan Thompson, Dr., University of Bath; Principal Investigator: Oly Perkin, Dr., University of Bath

Study record dates

Study Major Dates

• Study Start (Estimated): August 26, 2026
• Primary Completion (Estimated): August 27, 2027
• Study Completion (Estimated): August 27, 2027

Study Registration Dates

• First Submitted: September 15, 2026
• First Submitted That Met QC Criteria: September 19, 2026
• First Posted (Actual): September 23, 2026

Study Record Updates

• Last Update Posted (Actual): September 23, 2026
• Last Update Submitted That Met QC Criteria: September 19, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Keywords: Dietary Fibre; Fructo-oligosaccharides; Short-Chain Fatty Acids; Gastrointestinal Tolerability; Soluble Corn Fibre
• Other Study ID Numbers: 16901-21733

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No