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Completed

NCT Number: NCT05900609

Gut Health Enhancement by Eating Favourable Food

Within the GEEF om je buik study the effects of an 8-week intervention with either a diet rich in fiber or fermented food on the gut microbiota will be investigated.

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Key information

Conditions

Microbial Colonization Communicable Diseases Disease Attributes Infections Pathologic Processes Pathological Conditions, Signs and Symptoms

Age range

18 year–70 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Stichting Wageningen Research

Wageningen, Gelderland, 6708 WG, Netherlands

About this study

This study is a randomized controlled trial (RCT) with three intervention groups (high dietary fiber group (HDF), high fermented foods group (HFF), and a control group (CG)). The total duration of the study is 5 months and consists of an 8-week intervention (2-week ramp up period with dietary guidelines, followed by 6-week period with dietary guidelines + additional consumption of study products) and a follow-up after 3 months. In total 147 subjects will be included.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Men and Women, aged ≥18 - ≤70 years;
  • Being able to read and speak Dutch;
  • Willing to keep a stable dietary pattern throughout the study, apart from the dietary advice in the study;
  • Having a smartphone compatible with the Lifedata or PocketQ app to fill out the daily questionnaires.

Exclusion criteria

  • Having a disease or medical condition which can influence the study results such as diabetes, cancer, diagnosed irritable bowel syndrome, renal disease, liver enzyme abnormality, malignant neoplasm, or a history of inflammatory diseases (such as multiple sclerosis, rheumatoid arthritis, and inflammatory bowel disease);
  • Having a history of intestinal surgery that might interfere with study outcomes (this does not include an appendectomy or cholecystectomy);
  • Average dietary fiber intake of ≥18 gram (women) or ≥22 gram (men) per day, according to the fiber screen questionnaire (see F1 questionnaires);
  • More than 3 servings of fermented foods per day as assessed with the fermented food frequency questionnaire (see F1 questionnaires);
  • Having a Body Mass Index (BMI) of ≥ 30 kg/m2 (self-reported);
  • Currently following a strict diet and unwilling or unable to change; for example, a gluten free diet or a "crash diet" using meal substitutes;
  • Specific food allergies that interfere with dietary intervention (for example, gluten, lactose, etc);
  • Use of prebiotics, probiotics and/or synbiotics (this should be stopped 4 weeks before the start of the study) and use of fiber supplements;
  • Use of antibiotic treatment less than 3 months before start of the study and/or use of antibiotics during the study;
  • Use of medication that can interfere with the study outcomes, as judged by the medical supervisor;
  • Alcoholic use of ≥14 (women) or ≥28 (men) glasses of alcoholic beverages per week;
  • Use of soft or hard drugs (should be stopped at least 4 weeks before start of the study);
  • Being pregnant or lactating;
  • Participation in another clinical trial at the same time;
  • Student or employee working at either Food, Health and Consumer Research from Wageningen Food and Biobased Research, Microbiology at VU, the MLDS, at WholeFiber, Keep Food Simple or at Cidrani;
  • Unable to follow or comply to study rules.

Treatment and study plan

WholeFiber

Dietary Supplement

WholeFiberTM is a product with high levels of prebiotic dietary fibers (~85%) mainly consisting of inulin, and some pectin, hemi-cellulose and cellulose that is derived from the root vegetable, chicory roots.

Fiber guidelines:

Subjects receive a booklet with recipes high in fiber. Subjects are recommended to use 2 recipes + 2 snacks per day. Estimated average intake via the recipes in the recipe booklet is 24 grams/day.

General guidelines on nutrition and microbiome:

Subjects receive a link to a website with general recommendations to positively alter the gut microbiome (website Voedingscentrum and Dutch Digestive Foundation).

Other names: Chicory roots

Kombucha

Dietary Supplement

The kombucha is produced by a minimum three-month long fermentation process. It is a live fermented herbal drink essence, without refined sugar, and an unpasteurized, organic product.

Fermented food guidelines:

Study participants in the fermented foods arm are asked to use 3 additional servings of fermented food per day, using the fermented food list / recipe booklet.

General guidelines on nutrition and microbiome:

Subjects receive a link to a website with general recommendations to positively alter the gut microbiome (website Voedingscentrum and Dutch Digestive Foundation).

Other names: Fermented tea

Maltodextrin DE19/21

Dietary Supplement

Maltodextrin DE19/21 is a digestible carbohydrate, that is completely digested and does not reach the colon, which makes it a suitable placebo dietary compound and the reason why it is frequently used in comparable studies.

General guidelines on nutrition and microbiome:

Subjects receive a link to a website with general recommendations to positively alter the gut microbiome (website Voedingscentrum and Dutch Digestive Foundation).

Primary outcomes

  1. Microbiota diversity

    Time frame: Baseline (week 0)

    Microbial richness (ASV) using 16s rRNA

  2. Microbiota diversity

    Time frame: End ramp-up (week 2)

    Microbial richness (ASV) using 16s rRNA

  3. Microbiota diversity

    Time frame: End intervention (week 8)

    Microbial richness (ASV) using 16s rRNA

Secondary outcomes

  1. Gut microbiota composition

    Time frame: Baseline (week 0)

    16s rRNA

  2. Gut microbiota composition

    Time frame: End ramp-up (week 2)

    16s rRNA

  3. Gut microbiota composition

    Time frame: End intervention (week 8)

    16s rRNA

  4. Carbohydrate Active Enzymes (CAZymes)

    Time frame: Baseline (week 0)

    Relative abundance of CAZymes using shotgun metagenomic sequencing

  5. Carbohydrate Active Enzymes (CAZymes)

    Time frame: End ramp-up (week 2)

    Relative abundance of CAZymes using shotgun metagenomic sequencing

  6. Carbohydrate Active Enzymes (CAZymes)

    Time frame: End intervention (week 8)

    Relative abundance of CAZymes using shotgun metagenomic sequencing

  7. 92 inflammatory serum proteins

    Time frame: Baseline (week 0)

    92 protein biomarkers proteins associated with inflammatory and immune response processes measured in dried blood spots using the Olink target 96 panels. Expressed as normalized protein expression (NPX).

  8. 92 inflammatory serum proteins

    Time frame: End ramp-up (week 2)

    92 protein biomarkers proteins associated with inflammatory and immune response processes measured in dried blood spots using the Olink target 96 panels. Expressed as normalized protein expression (NPX).

  9. 92 inflammatory serum proteins

    Time frame: End intervention (week 8)

    92 protein biomarkers proteins associated with inflammatory and immune response processes measured in dried blood spots using the Olink target 96 panels. Expressed as normalized protein expression (NPX).

  10. Dietary intake

    Time frame: Baseline (week 0)

    Average intake of fiber, fermented foods and macronutrients using the Traqq app

  11. Dietary intake

    Time frame: End ramp-up (week 2)

    Average intake of fiber, fermented foods and macronutrients using the Traqq app

  12. Dietary intake

    Time frame: End intervention (week 8)

    Average intake of fiber, fermented foods and macronutrients using the Traqq app

  13. Dietary intake

    Time frame: End follow-up (5 months)

    Average intake of fiber, fermented foods and macronutrients using the Traqq app

  14. Gastrointestinal complaints

    Time frame: Daily during intervention (week 0 - week 8)

    Likert-point scale (scores 0 - 10), for bloating, flatulence and abdominal pain. A higher score means more bloating, flatulence and abdominal pain.

  15. Stool frequency

    Time frame: Daily during intervention (week 0 - week 8)

    Frequency of bowel movement per day

  16. Stool consistency

    Time frame: Daily during intervention (week 0 - week 8)

    Consistency per stool, based on Bristol Stool Score (type 1 -7). Scores 1-7. A higher score means more loose / watery stool.

  17. Abundance of Prevotella

    Time frame: Baseline (week 0)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  18. Abundance of Prevotella

    Time frame: End ramp-up (week 2)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  19. Abundance of Prevotella

    Time frame: End intervention (week 8)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  20. Abundance of Bacteroides

    Time frame: Baseline (week 0)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  21. Abundance of Bacteroides

    Time frame: End ramp-up (week 2)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  22. Abundance of Bacteroides

    Time frame: End intervention (week 8)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  23. Ratio of Prevotella/Bacteroides

    Time frame: Baseline (week 0)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  24. Ratio of Prevotella/Bacteroides

    Time frame: End ramp-up (week 2)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  25. Ratio of Prevotella/Bacteroides

    Time frame: End intervention (week 8)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  26. Microbial alpha diversity

    Time frame: Baseline (week 0)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  27. Microbial alpha diversity

    Time frame: End ramp-up (week 2)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  28. Microbial alpha diversity

    Time frame: End intervention (week 8)

    Based on a faecal smear image, using MicrobeLink tool from HORAIZON (AI, machine learning).

  29. Transit time

    Time frame: Baseline (week 0)

    Using blue dye method (two blue muffins)

  30. Transit time

    Time frame: End ramp-up (week 2)

    Using blue dye method (two blue muffins)

  31. Transit time

    Time frame: End intervention (week 8)

    Using blue dye method (two blue muffins)

  32. Sleep quality

    Time frame: Baseline (week 0)

    Athens insomnia scale. Score range: 0-28 points. Higher score means worse outcome.

  33. Sleep quality

    Time frame: End ramp-up (week 2)

    Athens insomnia scale. Score range: 0-28 points. Higher score indicates worse sleep quality.

  34. Sleep quality

    Time frame: End intervention (week 8)

    Athens insomnia scale. Score range: 0-28 points. Higher score indicates worse sleep quality.

  35. Sleep quality

    Time frame: End follow-up (5 months)

    Athens insomnia scale. Score range: 0-28 points. Higher score indicates worse sleep quality.

  36. Digestion associated Quality of Life

    Time frame: Baseline (week 0)

    Digestion associated Quality of Life (DQLQ) questionnaire. Score range: 0-9. Higher score indicates worse digestion associated quality of life.

  37. Digestion associated Quality of Life

    Time frame: End ramp-up (week 2)

    Digestion associated Quality of Life (DQLQ) questionnaire. Score range: 0-9. Higher score indicates worse digestion associated quality of life.

  38. Digestion associated Quality of Life

    Time frame: End intervention (week 8)

    Digestion associated Quality of Life (DQLQ) questionnaire. Score range: 0-9. Higher score indicates worse digestion associated quality of life.

  39. Digestion associated Quality of Life

    Time frame: End follow-up (5 months)

    Digestion associated Quality of Life (DQLQ) questionnaire. Score range: 0-9. Higher score indicates worse digestion associated quality of life.

  40. Well-being

    Time frame: Baseline (week 0)

    World Health Organisation (WHO)-Five Well-Being Index (WHO-5) questionnaire. Raw score ranges from 0-25. Final score is calculated by multiplying the raw score by 4. Final score range 0-100. Higher score indicates better well-being.

  41. Well-being

    Time frame: End ramp-up (week 2)

    World Health Organisation (WHO)-Five Well-Being Index (WHO-5) questionnaire. Raw score ranges from 0-25. Final score is calculated by multiplying the raw score by 4. Final score range 0-100. Higher score indicates better well-being.

  42. Well-being

    Time frame: End intervention (week 8)

    World Health Organisation (WHO)-Five Well-Being Index (WHO-5) questionnaire. Raw score ranges from 0-25. Final score is calculated by multiplying the raw score by 4. Final score range 0-100. Higher score indicates better well-being.

  43. Well-being

    Time frame: End follow-up (5 months)

    World Health Organisation (WHO)-Five Well-Being Index (WHO-5) questionnaire. Raw score ranges from 0-25. Final score is calculated by multiplying the raw score by 4. Final score range 0-100. Higher score indicates better well-being.

  44. Subjective health (perception and awareness)

    Time frame: Baseline (week 0)

    A 2-item questionnaire, which assesses how healthy participants perceive their own health and diet. Score range: 2 - 14, higher scores mean a higher subjective health

  45. Subjective health (perception and awareness)

    Time frame: End intervention (week 8)

    A 2-item questionnaire, which assesses how healthy participants perceive their own health and diet. Score range: 2 - 14, higher scores mean a higher subjective health

  46. Subjective health (perception and awareness)

    Time frame: End follow-up (5 months)

    A 2-item questionnaire, which assesses how healthy participants perceive their own health and diet. Score range: 2 - 14, higher scores mean a higher subjective health

  47. Intention to stay healthy (perception + awareness)

    Time frame: Baseline (week 0)

    A 3-item questionnaire, which assesses the extent to which participants have the intention to eat healthy. Score range: 3 - 21, higher scores mean more intention to stay healthy

  48. Intention to stay healthy (perception + awareness)

    Time frame: End intervention (week 8)

    A 3-item questionnaire, which assesses the extent to which participants have the intention to eat healthy. Score range: 3 - 21, higher scores mean more intention to stay healthy

  49. Intention to stay healthy (perception + awareness)

    Time frame: End follow-up (5 months)

    A 3-item questionnaire, which assesses the extent to which participants have the intention to eat healthy. Score range: 3 - 21, higher scores mean more intention to stay healthy

  50. Dietary intrinsic motivation (perception + awareness)

    Time frame: Baseline (week 0)

    A validated 6-item questionnaire, which assesses whether someone's motivation to eat healthy comes from within a person. Score range: 6 - 42, higher scores mean a higher intrinsic motivation.

  51. Dietary intrinsic motivation (perception + awareness)

    Time frame: End intervention (week 8)

    A validated 6-item questionnaire, which assesses whether someone's motivation to eat healthy comes from within a person. Score range: 6 - 42, higher scores mean a higher intrinsic motivation.

  52. Dietary intrinsic motivation (perception + awareness)

    Time frame: End follow-up (5 months)

    A validated 6-item questionnaire, which assesses whether someone's motivation to eat healthy comes from within a person. Score range: 6 - 42, higher scores mean a higher intrinsic motivation.

  53. Dietary self-efficacy (perception + awareness)

    Time frame: Baseline (week 0)

    A validated 8-item questionnaire, which assesses the extent to which one feels capable of eating healthy. Score range: 8 - 49, higher scores mean a higher self-efficacy

  54. Dietary self-efficacy (perception + awareness)

    Time frame: End intervention (week 8)

    A validated 8-item questionnaire, which assesses the extent to which one feels capable of eating healthy. Score range: 8 - 49, higher scores mean a higher self-efficacy

  55. Dietary self-efficacy (perception + awareness)

    Time frame: End follow-up (5 months)

    A validated 8-item questionnaire, which assesses the extent to which one feels capable of eating healthy. Score range: 8 - 49, higher scores mean a higher self-efficacy

  56. Self-regulation (perception + awareness)

    Time frame: Baseline (week 0)

    A 5-item questionnaire, which assesses the ability to plan and monitor actions. Score range: 5 - 35, higher scores mean a higher self-regulation

  57. Self-regulation (perception + awareness)

    Time frame: End intervention (week 8)

    A 5-item questionnaire, which assesses the ability to plan and monitor actions. Score range: 5 - 35, higher scores mean a higher self-regulation

  58. Self-regulation (perception + awareness)

    Time frame: End follow-up (5 months)

    A 5-item questionnaire, which assesses the ability to plan and monitor actions. Score range: 5 - 35, higher scores mean a higher self-regulation

  59. Subjective knowledge (perception + awareness)

    Time frame: Baseline (week 0)

    A validated 5-item questionnaire, which assesses how knowledgeable someone feels about nutrition and gut microbiota. Score range: 5 - 35, higher scores mean a higher subjective knowledge

  60. Subjective knowledge (perception + awareness)

    Time frame: End intervention (week 8)

    A validated 5-item questionnaire, which assesses how knowledgeable someone feels about nutrition and gut microbiota. Score range: 5 - 35, higher scores mean a higher subjective knowledge

  61. Subjective knowledge (perception + awareness)

    Time frame: End follow-up (5 months)

    A validated 5-item questionnaire, which assesses how knowledgeable someone feels about nutrition and gut microbiota. Score range: 5 - 35, higher scores mean a higher subjective knowledge

Other outcomes

  1. Body Mass Index (BMI)

    Time frame: Baseline (week 0)

    Weight and height will be combined to report BMI in kg/m^2

  2. Body Mass Index (BMI)

    Time frame: End ramp-up (week 2)

    Weight and height will be combined to report BMI in kg/m^2

  3. Body Mass Index (BMI)

    Time frame: End intervention (week 8)

    Weight and height will be combined to report BMI in kg/m^2

  4. Body Mass Index (BMI)

    Time frame: End follow-up (5 months)

    Weight and height will be combined to report BMI in kg/m^2

Sponsors and collaborators

Lead sponsor

VU University of Amsterdam

Other

Collaborators

  • Cidrani
  • Keep Food Simple
  • Maag Lever Darm Stichting
  • Wageningen University and Research
  • WholeFiber

Registry information

Acronym: GEEFomjebuik

Important dates

Study start
2023
Primary completion
2023
Study completion
2024
First posted
Jun 12, 2023
Registry last updated
Jul 8, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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