The Effect of Low or High Dietary Fiber Diet on Volatile Organic Compounds in Exhaled Breath of Healthy Individuals (FIBRE-MATCH)

Characterization of Fiber-degrading Microbiota in Individuals Without Gastrointestinal Diseases

The aim of this crossover intervention study is to evaluate the volatile organic compounds (VOCs) present in participants at baseline and how these levels change after consuming either a low- or high-dietary fiber diet for three days. This study will involve adults, 18-65 years old, without any gastrointestinal diseases.

The primary objectives are to characterize baseline VOC profiles, assess changes in these profiles after a short-term dietary fiber intervention, determine if specific VOC patterns correlate with dietary fiber intake, and identify the time points at which VOC levels peak. This information will help establish the optimal timing for breath sampling and potentially provide insight into how VOC patterns relate to dietary fiber consumption and degradation.

The expected outcome is that a high-dietary fiber diet will produce a VOC profile enriched in metabolites associated with fiber fermentation compared to a low-dietary fiber diet, and that these VOCs will be consistent with those identified in vitro during fecal fermentation. Each participant will serve as an internal control, enabling within-subject comparisons of VOC levels at baseline and following the dietary fiber intervention.

Participants will receive a whole-food product that is rich in dietary fiber and will consume either a low-fiber diet (10 g/day) or a high-fiber diet (40 g/day) for three days. On the first day of each intervention, participants will also ingest a pH capsule to monitor gastrointestinal pH continuously throughout the three days. After a three-week washout period, participants will cross over to the other intervention arm and undergo another round of gastrointestinal pH monitoring.

In addition to the dietary intervention, participants will complete food and health questionnaires to assess habitual fiber intake and dietary habits. Fecal samples will be collected for in vitro fermentation to functionally profile the gut microbiota by assessing fecal VOCs, short-chain fatty acids (SCFA), and the microbial enzymatic activity and its pH-dependent modulation.

Study Overview

• Status: Recruiting
• Conditions: Healthy Adults; Dietary Fiber Fermentation
• Intervention / Treatment: Other: Low, High Fiber Diet; Other: High, Low Fiber Diet

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

Contacts and Locations

• Study Contact: Name: Natalie Sundberg PhD Student; Phone Number: +46 704670585; Email: natalie.sundberg@oru.se
• Study Contact Backup: Name: Robert Brummer, Professor; Phone Number: +46 738426600; Email: Robert.Brummer@oru.se

Study Locations

• Sweden
  • Örebro, Sweden
    • Recruiting
    • Örebro University
    • Contact: Natalie Sundberg; Email: fibrematch@oru.se

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Signed informed consent obtained prior to any study-related procedures.
2. Willingness to refrain from regular consumption of prebiotic or probiotic products, as well as medications known to affect gastrointestinal function, for at least four weeks prior to the study visits.

Exclusion Criteria:

1. History of complicated gastrointestinal surgery.
2. Presence of a gastrointestinal diagnosis or any condition that, in the opinion of the principal investigator, may influence the study outcomes.
3. Current diagnosis of a psychiatric disorder.
4. Systemic use of antibiotics or steroid medications within the past 3 months.
5. Frequent use of NSAIDs (non-steroidal anti-inflammatory drugs) within the 2 months preceding the study visit.
6. Regular consumption of prebiotic or probiotic products within the past 4 weeks.
7. Alcohol or substance abuse.
8. Current smoking or use of nicotine pouches.
9. Frequent use of laxatives, antidiarrheal agents, or anticholinergic medications within the 12 weeks preceding the study visit.
10. Pregnancy or breastfeeding.
11. Respiratory disease or infection.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low Fiber Diet, Then High Fiber Diet; Participants will receive a whole food dietary fiber product to consume 10g of dietary fiber per day over a total of 3 days, equal to a high fiber diet. After a washout period of 3 weeks, they then receive the same whole food dietary fiber product, to consume 40g of dietary fiber per day in a total of 3 days, equal to a high fiber diet.	Other: Low, High Fiber Diet; Dietary Intervention: Low Fiber Diet Whole food dietary fiber product, 10g of dietary fiber consumed per day for 3 days Dietary Intervention: High Fiber Diet Whole food dietary fiber product, 40g of dietary fiber consumed per day for 3 days
Experimental: High Fiber Diet, Then Low Fiber Diet; Participants will receive a whole food dietary fiber product to consume 40g of dietary fiber per day over a total of 3 days, equal to a high fiber diet. After a washout period of 3 weeks, they then receive the same whole food dietary fiber product, to consume 10g of dietary fiber per day in a total of 3 days, equal to a high fiber diet.	Other: High, Low Fiber Diet; Dietary Intervention: High Fiber Diet Whole food dietary fiber product, 40g of dietary fiber consumed per day for 3 days Dietary Intervention: Low Fiber Diet Whole food dietary fiber product, 10g of dietary fiber consumed per day for 3 days

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effect of a 3-day low fiber diet compared to a 3-day high fiber diet on the Volatile Organic Compound profiles in exhaled breath	Volatile Organic Compound profiles in produced by the 3-day low fiber diet intervention compared to the profiles produced by the 3-day high fiber diet, with a 3-week washout inbetween	5 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effect of a low fiber diet on Volatile Organic Compound profiles after 4 hours	Volatile organic compound profiles 4 hours after the start of the low fiber diet intervention compared with baseline (0 hours)	4 hours
Effect of a low fiber diet on Volatile Organic Compound profiles after 6 hours	Volatile organic compound profiles 6 hours after the start of the low fiber diet intervention compared with baseline (0 hours)	6 hours
Effect of a low fiber diet on Volatile Organic Compound profiles after 8 hours	Volatile organic compound profiles 8 hours after the start of the low fiber diet intervention compared with baseline (0 hours)	8 hours
Effect of a high fiber diet on Volatile Organic Compound profiles after 4 hours	Volatile organic compound profiles 4 hours after the start of the high fiber diet intervention compared with baseline (0 hours)	4 hours
Effect of a high fiber diet on Volatile Organic Compound profiles after 6 hours	Volatile organic compound profiles 6 hours after the start of the high fiber diet intervention compared with baseline (0 hours)	6 hours
Effect of a high fiber diet on Volatile Organic Compound profiles after 8 hours	Volatile organic compound profiles 8 hours after the start of the high fiber diet intervention compared with baseline (0 hours)	8 hours
Gastrointestinal pH after a 3-day low fiber diet	Assessment of Gastrointestinal pH measured by the alpHaONE JSPC-1 pH capsule, after a 3-day low fiber diet	5 weeks
Gastrointestinal pH after a 3-day high fiber diet	Assessment of Gastrointestinal pH measured by the alpHaONE JSPC-1 pH capsule, after a 3-day high fiber diet	5 weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fecal Volatile Organic Compound profiles	Changes in fecal Volatile Organic Compound profiles produced during fecal fermentation, comparison of baseline (0 hours) profiles with profiles at 24 hours	1 week
SCFA	Changes in SCFA levels produced during fecal fermentation, comparison of baseline (0 hours) levels with levels at 24 hours	1 Week
Microbial enzymatic activity	Changes in microbial enzymatic activity during fecal fermentation, comparison of baseline (0 hours) activity with activity at 24 hours	1 week
Microbiota composition	Microbiota composition at baseline (0 hours) compared with composition at 24 hours	1 week

Collaborators and Investigators

• Sponsor: Örebro University, Sweden
• Collaborators: University of Helsinki; European Innovation Council
• Investigators: Study Director: Robert Brummer, Professor, Örebro University, Sweden

Study record dates

Study Major Dates

• Study Start (Estimated): May 25, 2026
• Primary Completion (Estimated): November 1, 2026
• Study Completion (Estimated): March 1, 2027

Study Registration Dates

• First Submitted: May 13, 2026
• First Submitted That Met QC Criteria: May 13, 2026
• First Posted (Actual): May 19, 2026

Study Record Updates

• Last Update Posted (Actual): June 4, 2026
• Last Update Submitted That Met QC Criteria: June 1, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Healthy participants; Volatile Organic Compounds; Dietary Fiber; Food Intervention; No gastrointestinal diseases; Without gastrointestinal diseases
• Other Study ID Numbers: 2026-00408-01; 101161484 (Other Grant/Funding Number: European Innovation Council (EIC))

Drug and device information, study documents

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