OAT-GUT-BRAIN: Effects of Oats and Rice on Comprehensive Health of Metabolically Challenged Individuals

OAT-GUT-BRAIN: Comprehensive Health Effects of Long-term Consumption of Oats in Metabolically Challenged Volunteers - Gut-mediated Metabolomics and Vitality

The overall objective of this research entity is to reveal the comprehensive health impact of oats in metabolically challenged individuals in a 6-week intervention, compared to that of rice. This is achieved by investigation of the lipids, short-chain fatty acids, inflammation markers and antioxidant status from plasma, fecal microbiome, and plasma metabolome. Additionally the effect of the 6-week diet on postprandial glycemia and postprandial satiety and vitality are investigated.

Study Overview

• Status: Active, not recruiting
• Conditions: Overweight and Obesity; High Blood Pressure; High Cholesterol/Hyperlipidemia
• Intervention / Treatment: Other: Dietary intervention; Other: Postprandial meal test

Detailed Description

Aims in this 6-week randomised, single-blinded clinical trial, including a postprandial study, with metabolically challenged volunteers on oat-rich low-gluten diet, are to:

1. Compare effect of oat and rice rich diets to blood lipid and glucose status, perceived gut and general well-being and dietary intake.
2. Investigate changes in fecal microbiome, SCFAs, plasma antioxidant status and inflammation markers resulting from consumption of oat or rice rich low-gluten diets.
3. Examine the impact of the oat or rice-rich low-gluten diet on the change in metabolite profiles in blood by non-targeted metabolomics approach.
4. Find out the long-term effects of oat and rice consumption on recovery and vitality by modulating the gut-brain axis and measured with neuropsychological testing and using tryptophan metabolites as biomarkers.
5. Discover how the long-term consumption of oats and rice and their possible alterations in fecal microbiome affect subsequent postprandial glycaemia and response of microbiota to the meal (as seen in plasma SCFAs).

• Study Type: Interventional
• Enrollment (Actual): 72
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Finland
  • Kuopio, Finland, 70211
    • Institute of Public Health and Clinical Nutrition, University of Eastern Finland
  • Turku
    • Turku, Turku, Finland, 20500
      • Food Sciences, Department of Life Technologies, University of Turku

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 30 years to 68 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Commits to follow the instructed low-gluten diet for 6 weeks
• 30 - 68 years of age
• BMI > 25 kg/m^2
• High cholesterol (without medication) characterized as total cholesterol > 5 mmol/l, AND either LDL > 3 mmol/l OR HDL (men/women) < 1.0/1.2 mmol/l AND/OR Hypertension (systolic > 140 mmHg or diastolic > 90 mmHg).

Exclusion Criteria:

• Regular medication that can affect the research outcomes (balanced medication for hypertension, hypo-/hyperthyroidism, hormone replacement therapy, and inhaled medicines allowed)
• Pregnancy or lactation
• Heavy smoking
• Recent course of antibiotics (less than 3 months prior to the study)

Study Plan

How is the study designed?

Design Details

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

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Oat-rich and low-gluten diet with oat-rich meal test; Participants will consume oats as the main cereal in their diet and follow low-gluten diet for 6 weeks. In postprandial meal test, they will be served an oat-rich breakfast.	Other: Dietary intervention; Changes in dietary intake, metabolism, fecal microbiome, vitality and perceived health after a 6-week consumption of oat or rice-rich low-gluten diet.; Other: Postprandial meal test; Postprandial changes after the 6-week consumption of either oat or rice-rich low-gluten diet, including blood markers, microbiome, satiety, recovery and vitality.
Active Comparator: Rice-rich low-gluten diet with oat-rich meal test; Participants will consume rice as the main cereal in their diet and follow low-gluten diet for 6 weeks. In postprandial meal test, they will be served an oat-rich breakfast.	Other: Dietary intervention; Changes in dietary intake, metabolism, fecal microbiome, vitality and perceived health after a 6-week consumption of oat or rice-rich low-gluten diet.; Other: Postprandial meal test; Postprandial changes after the 6-week consumption of either oat or rice-rich low-gluten diet, including blood markers, microbiome, satiety, recovery and vitality.
Experimental: Oat-rich low-gluten diet with rice-rich meal test; Participants will consume oats as the main cereal in their diet and follow low-gluten diet for 6 weeks. In postprandial meal test, they will be served a rice-rich breakfast.	Other: Dietary intervention; Changes in dietary intake, metabolism, fecal microbiome, vitality and perceived health after a 6-week consumption of oat or rice-rich low-gluten diet.; Other: Postprandial meal test; Postprandial changes after the 6-week consumption of either oat or rice-rich low-gluten diet, including blood markers, microbiome, satiety, recovery and vitality.
Active Comparator: Rice-rich low-gluten diet with rice-rich meal test; Participants will consume rice as the main cereal in their diet and follow low-gluten diet for 6 weeks. In postprandial meal test, they will be served a rice-rich breakfast.	Other: Dietary intervention; Changes in dietary intake, metabolism, fecal microbiome, vitality and perceived health after a 6-week consumption of oat or rice-rich low-gluten diet.; Other: Postprandial meal test; Postprandial changes after the 6-week consumption of either oat or rice-rich low-gluten diet, including blood markers, microbiome, satiety, recovery and vitality.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes from Baseline in Serum Total Cholesterol	Serum total cholesterol will be measured from fasting blood samples at the baseline (week 0) and after 6 week of the dietary intervention (week 6).	Week 0 and Week 6
Changes from Baseline in Interleukin-10	Interleukin-10 is measured from fasting plasma samples at the baseline (week 0) and after the 6-week diet intervention (week 6). It will be analysed as part of the Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden) that provides absolute quantities for 45 different proteins, such as interleukins, interferons, chemokines and growth factors that are related to inflammation.	Week 0 and Week 6

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes from Baseline in Blood Lipids	Cholesterols (HDL, LDL), Triglycerides and Free fatty acids (FFA) are measured from fasting blood samples before and after the 6-week dietary intervention.	Week 0 and Week 6
Changes from Baseline in Glucose Metabolism	Glucose and insulin are measured from fasting blood samples before and after the 6-week dietary intervention.	Week 0 and Week 6
Changes from Baseline in Inflammation markers	Inflammation markers of 45 different proteins, such as interleukins, interferons, chemokines and growth factors are measured from fasting plasma samples at the baseline before and after the 6-week diet intervention. The absolute quantities of the markers will be analysed with Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden).	Week 0 and Week 6
Changes from Baseline in Plasma metabolome	Circulating metabolites are measured from fasting plasma samples before and after the 6-week dietary intervention.	Week 0 and Week 6
Changes from Baseline in Plasma Tryptophan Metabolites	Circulating tryptophan metabolites are measured from fasting plasma samples before and after the 6-week dietary intervention to study modulation of the gut-brain-axis.	Week 0 and Week 6
Changes from Baseline in plasma Short-Chain Fatty Acids	Blood samples are taken at the fasting state before and after the 6-week diet intervention. Plasma is analysed by using UHPLC-MS to see the changes in plasma SCFA concentrations.	Week 0 and Week 6
Changes in Postprandial status of Peptide-YY (PYY) concentrations	PYY concentrations in blood are measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).	0, 15, 30, 45, 60, 90, 120, 180 minutes after the study meal at week 0 and week 6
Changes from Baseline in Plasma Antioxidant Capacity	The antioxidant status of plasma will be analysed with commercial kits of Ferric Reducing Antioxidant Power (FRAP) and Oxygen Radical Absorbance Capacity (ORAC) from fasting blood samples before and after the 6-week dietary intervention.	Week 0 and Week 6
Changes from Baseline in Fecal Microbiome	Stool samples are collected from the participants at the baseline (week 0) and after the 6-week diet intervention (week 6), and the metagenome is sequenced from the extracted DNA by shotgun metagenomics by Novogene GmbH (Munich, Germany). Changes in fecal microbiome during the dietary intervention are investigated by changes in alpha and beta diversities, taxonomy and metabolical pathways.	Week 0 and Week 6
Changes from Baseline in Blood Pressure	Blood pressure (systolic and diastolic) is measured twice, with a 1-min break between measurements at the baseline (week 0) and after the 6-week diet intervention (week 6).	Week 0 and Week 6
Changes from baseline in Anthropometric measurements	Weight (kg), height (cm), and waist circumference (cm) are measured after an overnight fast at the baseline (week 0) and after the 6-week diet intervention (week 6). BMI is calculated from the measured results.	Weeks 0 and 6
Changes from baseline in Dietary intake and Diet quality	Food records are collected from three consecutive weekdays and one weekend day at the baseline (week 0) and after the 6-week diet intervention (week 6). AivoDiet software (AivoDiet 2.2.0.0, Mashie, Malmö, Sweden) is used to calculate nutrient intake from the 4-day food records. Diet quality is measured through validated Food Frequency Questionnaire (FFQ) by Leppälä et al. (2010, doi: 10.1177/1403494810382476) including questions regarding oat and rice intakes to evaluate compliance to the study diet. FFQ is collected at the baseline, after 3 weeks of the diet and in the end of the intervention (week 6).	Week 0 and Week 6; FFQ on Week 0, 3 and 6
Changes from Baseline in Bowel movement frequency and Stool types	The changes in bowel movement frequency and stool consistency are recorded using a defecation record with the 7-step Bristol stool chart for the same 4 days as the food record. Participant will record the time of the bowel movement and the dominant type of the stool. The Bristol types will be categorized as hard (types 1 and 2), normal (types 3, 4, and 5), or loose stools (types 6 and 7).	Week 0 and Week 6
Changes from baseline in Gastrointestinal symptoms by GSRS	Gastrointestinal symptoms (self-reported) are measured by a Gastrointestinal Symptoms Rating Scale (GSRS) questionnaire at the baseline (week 0) and after the 6-week diet intervention (week 6). The GSRS results are rated according to the severity of a symptom and divided into subcategories of stomachache, bloating, flatulence, constipation, and diarrhea in addition to the total score. A higher score refers to more symptoms.	Weeks 0 and Week 6
Changes from baseline in Perceived well-being by RAND-36	Perceived well-being (self-reported) is measured by a RAND-36 questionnaire, derived from the Short Form-36 Health Survey (SF-36) at the baseline (week 0) and after the 6-week diet intervention (week 6). The RAND-36 answers are rated according to the instructions for indices that are then divided into scales of physical and social functionality, role limitations caused by physical and emotional health problems, bodily pain, general health perception, vitality, and mental health in addition to the total score. A higher score refers to better perceived health.	Weeks 0 and Week 6
Changes in Neuropsychological Performance: Cognitive Load	Established and well-validated computerised neuropsychological tests to measure cognitive load will be conducted both at the beginning and at the end of the intervention in connection with postprandial test. Inquisit software (Millisecond Software, Seattle, Washington, USA; https://www.millisecond.com/download/library/) is used for the cognitive load (Serial Sevens Task) test.	0 and 60 minutes after the study meal at week 0 and week 6
Changes in Neuropsychological Performance: Reaction Time and Attention	Established and well-validated computerised neuropsychological tests to measure reaction time and attention will be conducted both at the beginning and at the end of the intervention in connection with postprandial test. Inquisit software (Millisecond Software, Seattle, Washington, USA; https://www.millisecond.com/download/library/) is used for the reaction time and attention (Color Word Stroop test) test.	0 and 60 minutes after the study meal at week 0 and week 6
Changes in Neuropsychological Performance: Response Control	Established and well-validated computerised neuropsychological tests to measure response control will be conducted both at the beginning and at the end of the intervention in connection with postprandial test. Inquisit software (Millisecond Software, Seattle, Washington, USA; https://www.millisecond.com/download/library/) is used for the response control (Cued Go/No-Go Task) test.	0 and 60 minutes after the study meal at week 0 and week 6
Changes in Postprandial Glucose metabolism	Glucose and insulin in blood is measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).	0, 15, 30, 45, 60, 90, 120, 180 minutes after the study meal at week 0 and week 6

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in postprandial status of inflammation markers	Inflammation markers of 45 different proteins, such as interleukins, interferons, chemokines and growth factors are measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6). The absolute quantities of the markers will be analysed with Olink Target 48 Cytokine Panel (Olink Proteomics, Uppsala, Sweden).	0, 15, 30, 45, 60, 90, 120, 180 minutes after the study meal at week 0 and week 6
Changes postprandial status of Plasma Short-Chain Fatty Acids	SCFAs in blood are measured during 3 hours (3 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).	0, 90, 180 minutes after the study meal at week 0 and week 6
Changes in postprandial status of Plasma metabolome	Circulating metabolites are measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).	0, 15, 30, 45, 60, 90, 120, 180 minutes after the study meal at week 0 and week 6
Changes in postprandial status of Plasma Antioxidant Capacity	The antioxidant capacity of plasma is measured during 3 hours (8 time points) after consumption of the study meal (including the fasted state at 0 min). The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6). Commercial kits of Ferric Reducing Antioxidant Power (FRAP) and Oxygen Radical Absorbance Capacity (ORAC) will be used.	0, 15, 30, 45, 60, 90, 120, 180 minutes after the study meal at week 0 and week 6
Changes from Baseline in Satiety	Satiety related sensations are evaluated before and right after consuming the test meal and repetitively during 3 hours for 8 time points after the starting point of the consumption using 10 cm visual analogue scales (VAS) anchored with extremes (0 = not at all, 10 = extremely). The evaluated sensations are hunger, fullness, satiety, and desire to eat. The changed postprandial status is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).	0, 15, 30, 45, 60, 90, 120, 180 minutes after the study meal at week 0 and week 6
Changes from Baseline in Heart Rate Variability (HRV)	HRV is measured with Bittium Faros ECG Sensor that is attached with three electrodes to approx. 2 cm below the clavicles, about halfway of the bone horizontally (2 electrodes), as well as to the left at the bottom of the rib arch, approximately in the same vertical line with the upper electrode. HRV is measured through the full study day during the postprandial meal test and neuropsychological tests. The changed HRV is studied at the baseline (week 0) and after the 6-week diet intervention (week 6).	3,5 hours during the study day on Week 0 and Week 6
Changes from Baseline in Bile acids	Stool samples are collected from the participants at the baseline (week 0) and after the 6-week diet intervention (week 6), and the changes in fecal bile acids during the dietary intervention are investigated.	Week 0 and Week 6

Collaborators and Investigators

• Sponsor: University of Turku
• Collaborators: University of Eastern Finland

Publications and helpful links

General Publications

• Mannila E, Nuotio P, Kuosmanen A, De Storvik S, Karlund A, Jukkara A, Tauriainen MM, Narvainen J, Kolehmainen M, Linderborg KM. Comparison of Low-Gluten Diets Rich in Oats or Rice-A 6-Week Randomized Clinical Trial With Metabolically Challenged Volunteers. Mol Nutr Food Res. 2025 Jun;69(12):e70076. doi: 10.1002/mnfr.70076. Epub 2025 May 7.

Helpful Links

• Home page of the study, in Finnish

Study record dates

Study Major Dates

• Study Start (Actual): September 12, 2022
• Primary Completion (Actual): December 31, 2023
• Study Completion (Estimated): December 1, 2027

Study Registration Dates

• First Submitted: August 26, 2022
• First Submitted That Met QC Criteria: August 30, 2022
• First Posted (Actual): September 2, 2022

Study Record Updates

• Last Update Posted (Actual): April 13, 2026
• Last Update Submitted That Met QC Criteria: April 7, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Nutrition Disorders; Metabolic Diseases; Overnutrition; Body Weight; Dyslipidemias; Lipid Metabolism Disorders; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity; Hypertension; Hypercholesterolemia; Hyperlipidemias; Therapeutics; Nutrition Therapy; Diet Therapy
• Other Study ID Numbers: OGB

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Sensitive volunteer data may only be shared for collaborative research purposes with a separate agreement with the data owner. Metagenomic sequencing data can be found with identifier PRJEB104478 from ENA.
• IPD Sharing Time Frame: IPD will be available once the primary publications are published.
• IPD Sharing Access Criteria: Only for collaborative research purposes with a separate agreement with the data owner, the accessibility of data and documents can be decided together.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF; ANALYTIC_CODE

Drug and device information, study documents

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