Impact of Dietary Fibre Supplementation on Gut Symptoms in Healthy Participants (KiVa)

The Effect of Dietary Fibre Supplementation on Gastrointestinal Symptoms in Healthy Participants - KiVa-trial

Fibres found in food are mainly carbohydrates that are not broken down or absorbed during human digestion but instead pass to the colon to be fermented by microbes. Gases produced during bacterial fermentation (hydrogen, methane, and carbon dioxide), can cause unpleasant gastrointestinal symptoms in some individuals, such as bloating, flatulence, and stomach pain. Gas production varies between individuals and is influenced by the chemical structure of dietary fibres, the gut microbes' ability to ferment fibre, intestinal pH, and the transit time of intestinal contents. This randomized clinical trial in healthy adults will investigate how individual variations in the microbiome influence the level of gastrointestinal (GI) symptoms induced by different fibre types during short-term exposure.

Study Overview

• Status: Not yet recruiting
• Conditions: Gastrointestinal Symptoms
• Intervention / Treatment: Dietary supplement: cellulose; Dietary supplement: Oat fibre; Dietary supplement: Rye fibre

Detailed Description

The objective of this dietary intervention is to examine the effects of different dietary fibre types on gastrointestinal symptoms in apparently healthy adults and to investigate how these effects relate to the composition and functional capacity of the gut microbiota.

The study is designed as a randomized, crossover intervention trial with a total duration of approximately 6 weeks. A 5-day run-in phase is carried out to stabilize baseline dietary patterns and ensure adherence to study procedures. During the intervention, each participant consumes 3 different fibre-rich products, with each product administered for 4 consecutive days (referred to as a "fibre period"). Each fibre period is separated by a 10-day washout period.

Participants (n=28) are apparently healthy adult males and females aged 18-65 years who experience gastrointestinal/ digestive discomfort during or after eating. Individuals without such symptoms are unlikely to exhibit measurable responses, which would limit the ability to address the study's primary research questions.

During the 4-day fibre period, the daily fibre dose provided by the study product is 20 g for women and 25 g for men (corresponding to 2.5 g of fibre per MJ of energy intake, assuming daily energy intake of 8 MJ for women and 10 MJ for men). During the trial, participants consume three structurally different types of dietary fibre: cellulose (poorly fermentable fibre; microcrystalline cellulose), beta-glucan rich fibre (oat bran-based fibre product), and arabinoxylan rich fibre (rye bran-based fibre product). Participants are randomly assigned into one of the six predefined intervention sequences, which represent all possible orders of exposure to the 3 fibre products. Sequence allocation will be generated prior to enrolment, and participants will receive each fibre-rich test product in a randomized order. Participants are instructed to keep the rest of their diet as habitual as possible during the study. Regular use of dietary supplements must be discontinued for the study duration

Participants report their daily GI symptoms as well as perceived stress and mood through a symptom questionnaire using a mobile app. A total of nine GI symptoms are reported (i.e., stomach/ abdominal pain, stomach cramps, bloating, flatulence, borborygmus, nausea, heartburn, discomfort in the upper abdomen/ unpleasant sensation of fullness following eating, a sudden need to defecate), and their severity of symptoms is assessed on a 0-100 VAS scale. Participants report daily the number of bowel movements through the online form, as well as their daily amount of physical activity. In addition, physical activity is assessed using an accelerometer. Dietary intake is assessed by food records (3-day food records during the run-in period and 2-day food records during each fibre period).

Stool samples are used for the analysis of the gut microbiota and metabolome. Additionally, the the effects of different fibre types on metabolic profiles in blood, urine, and stool samples (including SCFAs), as well as on gases in exhaled breath will be analysed.

• Study Type: Interventional
• Enrollment (Estimated): 28
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Anne-Maria Pajari, Professor; Phone Number: +358294158203; Email: anne-maria.pajari@helsinki.fi
• Study Contact Backup: Name: Maija Marttinen, PhD; Phone Number: +358294158209; Email: maija.marttinen@helsinki.fi

Study Locations

• Finland
  • Uusimaa
    • Helsinki, Uusimaa, Finland
      • Department of Food and Nutrition, University of Helsinki
      • Contact: Anne-Maria Pajari, Professor; Phone Number: +358294158203; Email: anne-maria.pajari@helsinki.fi
      • Contact: Maija Marttinen, PhD; Phone Number: +358294158209; Email: maija.marttinen@helsinki.fi

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• healthy male and female
• aged 18-65 years
• experience gastrointestinal discomfort during or after eating
• willing to commit to the 6-week study period and follow the study schedule.

Exclusion Criteria:

• Body mass index ≤ 18.5 or ≥ 35 kg/m².
• Inflammatory bowel diseases, irritable bowel syndrome (IBS), celiac disease, endocrine or lipid metabolism disorders, liver or kidney diseases, cancer within the past 5 years, eating disorders.
• Medication for gastrointestinal symptoms, bowel function, diabetes, or hypercholesterolemia.
• Regular or recent use of antibiotics (within the last 3 months).
• Food allergies to the ingredients of the study products.
• Heavy, long-duration exercise several times a week.
• Smoking, use of snus or nicotine pouches.
• Planned or ongoing pregnancy or breastfeeding.
• In addition, the site-specific principal investigator may exclude a person due to any illness, medication, or factor they deem relevant for the participant's health and safety or for the conduct of the study.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cellulose; poorly fermentable fibre, "negative control"	Dietary supplement: cellulose; Microcrystalline cellulose; daily dose of fibre from the study product 20 g for females and 25 g for males on 4 consecutive days
Experimental: Oat fibre; fibre-rich product from oat bran	Dietary supplement: Oat fibre; Oat bran-based fibre product; daily dose of fibre from the study product 20 g for females and 25 g for males on 4 consecutive days
Experimental: Rye fibre; fibre-rich product from rye bran	Dietary supplement: Rye fibre; Rye bran-based fibre product; daily dose of fibre from the study product 20 g for females and 25 g for males on 4 consecutive days

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intensity of gastrointestinal symptoms, total score	The composite score of the intensity of individual gastrointestinal symptoms reported on a VAS scale by the participants.	6 weeks Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of stomach/ abdominal pain	Intensity of experienced stomach/ abdominal pain reported on a VAS scale from zero (no pain) to 100 (very intense pain) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of bloating	Intensity of experienced bloatingreported on a VAS scale from zero (no symptoms) to 100 (very intense symptoms) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of stomach cramps	Intensity of experienced stomach cramps reported on a VAS scale from zero (no pain) to 100 (very intense pain) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared
Intensity of flatulence	Intensity of experienced flatulence reported on a VAS scale from zero (no symptoms) to 100 (very intense symptoms) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of borborygmus	Intensity of experienced borborygmus reported on a VAS scale from 0 (no symptoms) to 100 (very intense symptoms) by the participants on daily basis	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of nausea	Intensity of experienced nausea reported on a VAS scale from 0 (no symptoms) to 100 (very intense symptoms) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of heartburn	Intensity of experienced heartburn reported on a VAS scale from 0 (no symptoms) to 100 (very intense symptoms) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of discomfort in the upper abdomen or unpleasant sensation of fullness following eating	Intensity of experienced discomfort or unpleasant sensation reported on a VAS scale from 0 (no symptoms) to 100 (very intense symptoms) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Intensity of a sudden need to defecate	Intensity of experienced discomfort or unpleasant sensation reported on a VAS scale from 0 (no symptoms) to 100 (very intense symptoms) by the participants on daily basis.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Composition and function of gut microbiome	Microbiota-related analyses of the collected stool samples are carried out using DNA-based methods	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Number of bowel movements	Number of bowel movements reported by participants on daily basis using a mobile app.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Breath gases	Hydrogen and methane measured from exhaled breath samples during run-in and fibre periods.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Fecal and blood SCFA	Analysis of short chain fatty acids (SCFA) from stool and blood samples	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Dietary intake	The intake of dietary fibre and nutrients calculated from food records during run-in and fibre periods.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Physical activity	Level of physical activity and inactivity determined using an accelerometer during run-in and fibre periods.	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.
Metabolomics from feces, blood and urine	Targeted/untargeted analysis of fecal, blood and urine metabolome	6 weeks. Differences between the fibre periods and fibre periods and run-in period will be compared.

Collaborators and Investigators

• Sponsor: University of Helsinki

Study record dates

Study Major Dates

• Study Start (Estimated): August 17, 2026
• Primary Completion (Estimated): September 30, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: May 7, 2026
• First Submitted That Met QC Criteria: May 7, 2026
• First Posted (Actual): May 14, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 7, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: microbiome; microbiota; dietary fibre; dietary fiber; gastrointestinal discomfort; gut symptoms
• Additional Relevant MeSH Terms: Carbohydrates; Polymers; Macromolecular Substances; Biomedical and Dental Materials; Manufactured Materials; Technology, Industry, and Agriculture; Polysaccharides; Glucans; Biopolymers; Cellulose
• Other Study ID Numbers: FIBRE-MATCH Helsinki Pilot; 101161484 (Other Grant/Funding Number: European Innovation Council (EIC))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Data sharing in agreement with the EU General Data Protection Regulation

Drug and device information, study documents

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