Impact of Soluble Arabinoxylan and Rice Bran Fiber on the Gut Microbiome in Healthy Adults

RDA Cereal Fiber Clinical

The importance of the gut microbiota for general health has been recently elucidated, but little is known about the impact of different types of nutrients on the gut microbiota. The soluble fiber in cereal by-products, arabinoxylan (AX), is known to be beneficial for generally promoting gut health. However, it is unclear whether consuming rice bran (RB), the source of AX, is equally helpful or better than consuming the extracted form of AX. This study aims to reveal the potential benefit of insoluble cereal bran fiber ingredients by comparing the effect of soluble arabinoxylan fiber alone and the mostly insoluble rice bran fiber, containing arabinoxylan, on intestinal health and gut microbiota. A placebo (maltodextrin) will be used as a control, with no significant changes expected in this group for the evaluated outcomes.

Participants will:

• Consume two different fiber supplements (soluble arabinoxylan or stabilized rice bran) as well as a placebo (maltodextrin) for 3 weeks each, separated by a 2-week washout period.
• Provide blood and stool samples at six different time points.
• Complete a food and gastrointestinal symptom diary during the intervention periods.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy
• Intervention / Treatment: Dietary supplement: Soluble Arabinoxylan; Dietary supplement: Rice Bran; Dietary supplement: Maltodextrin (Placebo)

Detailed Description

Background:

This randomized, crossover clinical trial aims to evaluate the effects of two types of dietary fibers (soluble arabinoxylan and rice bran) compared to a control (maltodextrin) on gut microbiota and intestinal health in healthy adults aged 18-45. Insoluble rice bran, a fiber derived as a cereal by-product, may provide special support of a group of beneficial gut bacteria, and may compare well to its soluble arabinoxylan counterpart. This study will provide insights into whether rice bran, as a fiber source, offers additional benefits compared to the extracted soluble form alone.

Significance:

This study will contribute to the understanding of how different types of cereal fibers, specifically soluble arabinoxylan and rice bran, influence gut microbiota composition and overall intestinal health. The findings will have implications for dietary interventions aimed at promoting gut health, especially in relation to fiber intake from whole food sources compared to extracted fiber components.

Sample size:

25 subjects will be enrolled in the study to have a final number of at least 21, considering a 20% dropout rate.

The study involves three arms:

1. Soluble arabinoxylan: Participants will consume 10 grams of soluble arabinoxylan diluted in 200 mL of water, twice daily (morning and evening), for 3 weeks.
2. Rice bran: Participants will consume 10 grams of defatted, stabilized rice bran diluted in 200 mL of water, twice daily (morning and evening) for 3 weeks.
3. Maltodextrin: Participants will consume 10 grams of maltodextrin diluted in 200 mL of water, twice daily (morning and evening) for 3 weeks.

A two-week washout period will separate the three intervention phases to minimize carryover effects. The order in which participants receive the interventions will be randomized before the study starts.

Study Objectives:

The primary objective is to determine if rice bran fiber promotes the growth of Clostridium cluster IVa, a butyrate-producing bacterial group known to be beneficial for gut health. The secondary objective is to assess differences in the composition of gut microbiota and short-chain fatty acid production among the three interventions. Blood samples will be analyzed for barrier function proteins to further understand how each supplement influences gut integrity.

Study Procedures:

• Screening: Participants will undergo pre-screening via an online questionnaire and those who meet the criteria, will attend an in-person visit for physical measurements (height, weight, and BMI calculation) at the Clinical Research Center at Purdue University. A small amount of blood will be drawn for general health assessment.
• Interventions: Candidates who fully meet the inclusion criteria will be enrolled in the study. Once a week, they will stop at the Department of Food Science at Purdue University to receive sachets containing one of the three supplements described above. Participants will be instructed to consume one sachet in the morning and one in the evening, diluted in water. Each treatment will last for three weeks, followed by a two-week washout period.
• Sample Collection: Biological samples will be collected on the first and the last day of each intervention (days 1, 21, 35, 56, 70, and 91) and include stool and blood collection.
• The participants will be required to fill out a Diet History Questionnaire (DHQ) at the baseline (week 0) and at the end of the study (13th week) to evaluate whether changes in their dietary patterns occurred. 24-hour dietary recalls will also be administered at specific time points during the study to estimate nutrient intake (weeks 0, 1, 2, 3, 5, 6, 7,8, 10, 11, 12, and 13). Lastly, the short form of the International Physical Activity Questionnaire (IPAQ) will be applied at baseline (week 0) and the end of each treatment arm (weeks 3, 8, and 13) to evaluate the participants' physical activity patterns, as well as any eventual shifts throughout the study.
• Additionally, participants will be asked to complete a food and gastrointestinal symptom diary everyday during the intervention periods.

Data Analysis:

Gut microbiota composition will be assessed using DNA sequencing of stool samples, while blood samples will be analyzed for intestinal barrier function markers. Additionally, short-chain fatty acid concentrations in the stool will be measured to understand the metabolic effects of each fiber type on the gut microbiota.

• Study Type: Interventional
• Enrollment (Estimated): 25
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Bruce R Hamaker, Ph.D.; Phone Number: 765-494-5668; Email: hamakerb@purdue.edu
• Study Contact Backup: Name: Mirian A de Campos Costa, Ph.D.; Phone Number: 765-496-3802; Email: decampos@purdue.edu

Study Locations

• United States
  • Indiana
    • West Lafayette, Indiana, United States, 47907
      • Clinical Research Center at Purdue University
      • Contact: Robin L Rhine; Phone Number: 765-494-6275; Email: rrhine@purdue.edu

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Men or women.
• Aged between 18-45 years.
• Body mass index between 18.5 and 25 kg/m².
• Able to read/speak English.

Exclusion Criteria:

• Gastrointestinal disorders (inflammatory bowel disease, irritable bowel syndrome, gluten sensitivity/intolerance, etc.).
• Those who took antibiotics 3 months before the study.
• Individuals taking regular medication or supplements that might affect the gut microbiota.
• Individuals undertaking weight-loss diets.
• Unstable body weight (±3 kg in the past 3 months), and individuals below 110 lb.
• Heavy drinkers (for men, consuming more than 4 drinks on any day or more than 14 drinks per week; for women, consuming more than 3 drinks on any day or more than 7 drinks per week).
• Smokers (those who have smoked 100 cigarettes in their lifetime and who currently smoke cigarettes, even every day or occasionally).
• Breastfeeding or pregnant women.

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
Experimental: Soluble Arabinoxylan; Participants in this arm will receive soluble arabinoxylan for 3 consecutive weeks.	Dietary supplement: Soluble Arabinoxylan; 10 grams of soluble arabinoxylan diluted in 200 mL of water, twice daily for 3 consecutive weeks.
Experimental: Rice Bran; Participants in this arm will consume rice bran fiber for 3 consecutive weeks.	Dietary supplement: Rice Bran; 10 grams of rice bran fiber diluted in 200 mL of water, twice daily for 3 consecutive weeks.
Placebo Comparator: Maltodextrin; Participants in this arm will consume maltodextrin for 3 consecutive weeks.	Dietary supplement: Maltodextrin (Placebo); 10 grams of maltodextrin diluted in 200 mL of water, twice daily for 3 consecutive weeks.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparison of two test fibers (insoluble cereal bran and soluble arabinoxylan) and a control (maltodextrin) on gut beneficial bacteria	The primary outcome of the study is change in butyrogenic Clostridium cluster XIVa gut bacteria.	From enrollment to the end of treatment at 13 weeks.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparison of two tests (insoluble cereal bran and soluble arabinoxylan) and a control (maltodextrin) on fecal butyrate and intestinal barrier function	Secondary outcomes are fecal butyrate, gut barrier function protein (serum zonulin), and serum lipopolysaccharide-binding protein (LBP)	From enrollment to the end of treatment at 13 weeks.

Collaborators and Investigators

• Sponsor: Purdue University
• Collaborators: Rural Development Administration (RDA) of the Republic of Korea

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2025
• Primary Completion (Estimated): October 1, 2025
• Study Completion (Estimated): October 1, 2025

Study Registration Dates

• First Submitted: March 6, 2025
• First Submitted That Met QC Criteria: March 6, 2025
• First Posted (Actual): March 12, 2025

Study Record Updates

• Last Update Posted (Actual): June 29, 2025
• Last Update Submitted That Met QC Criteria: June 25, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Keywords: Gut microbiota; Dietary fiber; Intestinal health; Short-Chain Fatty Acids; Soluble arabinoxylan; Rice bran fiber; Butyrate-producing bacteria; Clostridium cluster IVa
• Other Study ID Numbers: IRB-2024-881

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No