PsylliumMERLINNCT05906589
Exploring Mechanism of Action of Dietary Fibre on the Gut Microbiota and Metabolites
A study testing Inulin, Psyllium and Maltodextrin in people with Psyllium and Inulin, run by University of Aberdeen at 1 site in United Kingdom.
Trial summary
Cancer patients receiving pelvic radiotherapy suffer side effects to the intestine, including diarrhoea and occasionally rectal bleeding, often worsened by chemoradiation. Many pelvic radiotherapy patients receive a form of dietary fibre, psyllium husk, to manage their diarrhoeal symptoms. Read more about this study
- Who is it for?
- Ages 60 years and olderHealthy volunteers can take part
- What is being tested?
- Inulin, Psyllium and Maltodextrin
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 40 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 7 Sep 2023to 10 Jul 2025
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 60 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- >60 years old
Who cannot join
- Medication exclusion criteria:
- Oral antibiotic use (within the past 3 months due to impact on gut microbiota).
- Anti-coagulants (Warfarin).
- Carbamazepine (epilepsy)
- Digoxin (heart conditions)
- Mesalazine (gut problems)
Show all 19Show fewer
- Regular use of anti-constipation medication/laxatives.
- Medical exclusion criteria:
- Food allergies, self-reported food sensitivity or intolerance.
- Type 1 or Type 2 diabetes.
- Coeliac disease or gluten intolerance.
- Metformin intake.
- Bowel obstruction
- Muscle weakness of the bowel
- Phenylketonuria.
- Other exclusion criteria:
- Anyone with unsuitable veins for blood sampling.
- Anyone with chronic constipation (>3 days without defaecation).
- Anyone who is unable to fluently speak, read and understand English.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Exploring Mechanism of Action of Dietary Fibre on the Gut Microbiota and Metabolites: Can we Identify Responders and Non-responders to Psyllium and Inulin Dietary Fibres?
Cancer patients receiving pelvic radiotherapy suffer side effects to the intestine, including diarrhoea and occasionally rectal bleeding, often worsened by chemoradiation. Many pelvic radiotherapy patients receive a form of dietary fibre, psyllium husk, to manage their diarrhoeal symptoms. There is evidence in mice that dietary fibre supplementation can improve tumour response and reduce normal tissue side effects caused by radiation. If this were to be confirmed in humans, it would be a major advance in patient treatment. The investigators will conduct a study in healthy subjects to assess mechanisms and response to dietary fibre.
The investigators will conduct a within-subject diet intervention study on healthy older adults (>60 years old) to determine if a subset of the population are responders to dietary fibre manipulation, using inulin with or without psyllium. This will allow assessment of the physiological impact of dietary fibre. Participants will receive placebo, inulin, or psyllium plus inulin in random order (6 possible combinations) for two weeks each with two-week washout periods.
Baseline faecal microbial activity, short chain fatty acid (SCFA) concentrations, and habitual fibre intake, determined by dietary questionnaires/food diaries will be used to identify individuals in whom dietary fibre manipulation might have a positive impact. Individuals who respond to dietary fibre supplementation may be found to have elevated levels of some SCFAs and significantly increased relative abundance of certain microbiota. Dietary parameters, bacterial relative abundance and SCFA levels will be correlated with plasma cytokine levels.
Read the detailed description
Of all patients receiving radiotherapy for cancer in 2018 and 2019, 28.6% were treated for a pelvic malignancy. The dose of radiotherapy necessary to cure the tumour often causes side effects in the surrounding healthy tissues, which can significantly impact the patients quality of life. Chemoradiation, the addition of chemotherapy to radiotherapy, improves tumour cure rates by radiosensitising the tumour, but at the expense of worsened normal tissue effects. Most patients over 80 years are unable to tolerate chemoradiation. With an aging population, there is an urgent clinical need to find alternatives to chemoradiation.
A difference in the composition and diversity of the gut microbiota has been found in responders versus non-responders to immunotherapy and in patients experiencing different levels of toxicities following radiotherapy. This indicates that the microbiota could be used to predict, prevent, or treat radiation enteropathy. An often-found side effect in pelvic radiotherapy patients is diarrhoea. Many pelvic radiotherapy patients receive a form of dietary fibre, known as psyllium husk (ispaghula husk or FybogelTM) to manage their diarrhoeal symptoms. Dietary fibres like psyllium and inulin are non-digestible carbohydrates found in fruits, vegetables, whole grains and legumes. They are anaerobically fermented by the gut bacteria, producing SCFAs, including acetate, propionate, and butyrate. SCFAs are the main performers in the interplay between diet, microbiota and health, and have anti-inflammatory and also anti-tumorigenic properties.
A high intake of dietary fibre is proven to decrease the risk of type 2 diabetes, colon cancer and cardiovascular disease by reducing the digestion and absorption of macronutrients and decreasing the contact time of carcinogens with the intestinal lumen. There is emerging evidence that the inclusion of dietary fibre supplements in the diet could modify the tumour response to radiotherapy. If confirmed in humans, this would be a major advance in patient treatment.
In a mouse model of colitis, exhibiting similar acute symptoms to those due to radiotherapy, the addition of psyllium in the diet reduced colonic inflammation and protected intestinal tight junctions. This prevented penetration of luminal inflammatory molecules through the gut wall. In a similar model system, psyllium reduced the severity of colitis in C57BL/6 specific pathogen-free and germ-free mice, via microbiota-dependent and independent mechanisms.
Inulin, another dietary fibre, is rapidly fermented in the proximal large intestine. Here, it selectively increases the growth of the butyrate producer Faecalibacterium prausnitzii and Bifidobacterium spp.. Bifidobacteria are associated with anti-tumour effects and augmented dendritic cell function leading to increased Cytotoxic T-cell (CD8+) priming and accumulation in the tumour microenvironment.
The investigators found promising preliminary data in our mouse studies, indicating that psyllium with inulin enhances tumour control. Immunodeficient mice fed a 10% inulin diet had an improved tumour control following 6 gray (Gy) ionising radiation. Immunocompetent mice showed a delayed tumour growth when receiving psyllium plus inulin when compared to a normal or low fibre diet, accompanied by significantly increased tumour infiltration of cytotoxic T cells. Psyllium plus inulin also significantly increased the percentage of intestinal remaining after 14 Gy compared to a low fibre diet or psyllium alone. A psyllium plus inulin diet also modified intestinal immunity, particularly B cells. Furthermore, in mouse bladder cancer cell UPPL 1591-derived allografts, CD8+ (cytotoxic) T cells scored higher for psyllium and psyllium plus inulin than psyllium plus resistant starch. However, compared to humans, inbred mice are genetically more similar and are held in controlled environmental conditions, so humans are likely to demonstrate more variability in response to dietary fibre intervention.
The investigators will study a group of human participants to assess tolerance and responses to inulin and psyllium plus inulin, in terms of intestinal side effects, significant alterations in the microbiota, levels of SCFAs in plasma and faeces, and plasma inflammatory cytokines. The investigators will also investigate whether responders and non-responders within the study can be identified from baseline dietary information and/or microbial activity (based on faecal SCFA measurements), as an individual's current diet will influence their response to dietary fibre modification.
- Being tested
- Inulin, Psyllium, Maltodextrin
- Keywords
- Dietary fibre, Dietary fiber, Gut microbiota
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
InulinDietary supplement
The participant will take inulin twice daily over a 14 day period.
PsylliumDietary supplement
Also called Ispaghula husk
The participant will take psyllium twice daily over a 14 day period.
MaltodextrinDietary supplement
The participant will take maltodextrin twice daily over a 14 day period.
| Study group | Role | What they receive |
|---|---|---|
| Inulin | Experimental | The participant will be asked to administer the provided doses of 8g inulin twice daily. Receives: Dietary Supplement: Inulin |
| Inulin + psyllium | Experimental | The participant will be asked to administer the provided doses of 8g inulin + 3.5g psyllium twice daily. Receives: Dietary Supplement: Inulin; Dietary Supplement: Psyllium |
| Maltodextrin | Placebo comparator | The participant will be asked to administer the provided doses of 8g maltodextrin twice daily. Receives: Dietary Supplement: Maltodextrin |
What is being measured
The primary outcome is the main question the study is designed to answer.
Microbial composition using 16S sequencing
To explore the effect of inulin and psyllium plus inulin on microbial composition at baseline and after a 14-day intervention.
Measured: 11 weeks per participant
Short Chain Fatty Acid (SCFA) levels
To explore the effect of inulin and psyllium plus inulin on short chain fatty acid levels at baseline and after a 14-day intervention.
Measured: 11 weeks per participant
Secondary outcomes (9)
Tolerability of Inulin defined by questionnaire 'quality of life' and 'gastrointestinal wellbeing'
To determine if 16 g inulin with or without 7 g psyllium dietary interventions are tolerable in older adults (>60 years old) assessed by completing gastrointestinal wellbeing questionnaires and quality of life questionnaires (SF36).
Measured: 11 weeks per participant
Tolerability of psyllium defined by questionnaire 'quality of life SF36' and 'gastrointestinal wellbeing'
To determine if 16 g inulin with or without 7 g psyllium dietary interventions are tolerable in older adults (>60 years old) assessed by completing gastrointestinal wellbeing questionnaires and quality of life questionnaires (SF36).
Measured: 11 weeks per participant
Rate of habitual fibre intake before and during the intervention
To determine if Food Frequency Questionnaires/3- day weighed food diaries (to assess habitual fibre intake before and during the intervention) can identify individuals in whom dietary fibre supplementation would have a positive impact on microbiota composition and SCFA levels.
Measured: 11 weeks per participant
Faecal SCFA concentrations
Identify individuals in whom dietary fibre supplementation would have a positive impact using baseline faecal microbial activity (determined by faecal SCFA concentrations).
Measured: 11 weeks per participant
Elevated plasma SCFAs
Change in SCFA levels in plasma from baseline in individuals that respond to dietary fibre supplementation after 14 days.
Measured: 11 weeks per participant
A 0.5 log10 change in health-associated Bifidobacterium spp. from baseline
Detecting a 0.5 log10 change in health-associated Bifidobacterium spp. from baseline in individuals given psyllium plus inulin using faecal quantitative polymerase chain reaction.
Measured: 11 weeks per participant
Plasma cytokine IL-6
To determine if dietary parameters, bacterial relative abundances and SCFA levels are correlated with plasma cytokine IL-6 level (cytokine level will only be measured at the end of each intervention), which may influence radiotherapy outcomes in terms of tumour response and normal tissue effects.
Measured: 11 weeks per participant
Plasma cytokine IL-8
To determine if dietary parameters, bacterial relative abundances and SCFA levels are correlated with plasma cytokine IL-8 level (cytokine level will only be measured at the end of each intervention), which may influence radiotherapy outcomes in terms of tumour response and normal tissue effects.
Measured: 11 weeks per participant
Immunoglobulin A (IgA) and calprotectin levels
To determine if the interventions alter gut health and inflammation, measured by faecal IgA and calprotectin at the end of each of the three interventions.
Measured: 11 weeks per participant
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 Jun 2023
- Study start7 Sep 2023
- Primary completion10 Jul 2025
- Study completion10 Jul 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (14)Papers the sponsor has linked to this study.
- Other trials for PsylliumStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- The participants will be randomly allocated to one of the 6 different intervention combinations for the supplements ((A) placebo; (B) inulin; (C) psyllium plus inulin) with the same number of participants in each of the combinations. There are 6 possible combinations: * A \> B \> C * B \> A \> C * C \> B \> A * A \> C \> B * C \> A \> B * B \> C \> A
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 40 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Aberdeen
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Anne E Kiltie, Prof, Principal investigator, University of Aberdeen
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05906589
- Sponsor's protocol ID
- 501
- Acronym
- MERLIN
- Status last verified
- Feb 2026
- First submitted
- 19 May 2023
- Last updated
- 12 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: No.
Publications
Wang L, Wang X, Zhang G, Ma Y, Zhang Q, Li Z, Ran J, Hou X, Geng Y, Yang Z, Feng S, Li C, Zhao X. The impact of pelvic radiotherapy on the gut microbiome and its role in radiation-induced diarrhoea: a systematic review. Radiat Oncol. 2021 Sep 25;16(1):187. doi: 10.1186/s13014-021-01899-y.
PubMed 34563216Bishehsari F, Engen PA, Preite NZ, Tuncil YE, Naqib A, Shaikh M, Rossi M, Wilber S, Green SJ, Hamaker BR, Khazaie K, Voigt RM, Forsyth CB, Keshavarzian A. Dietary Fiber Treatment Corrects the Composition of Gut Microbiota, Promotes SCFA Production, and Suppresses Colon Carcinogenesis. Genes (Basel). 2018 Feb 16;9(2):102. doi: 10.3390/genes9020102.
PubMed 29462896Carretta MD, Quiroga J, Lopez R, Hidalgo MA, Burgos RA. Participation of Short-Chain Fatty Acids and Their Receptors in Gut Inflammation and Colon Cancer. Front Physiol. 2021 Apr 8;12:662739. doi: 10.3389/fphys.2021.662739. eCollection 2021.
PubMed 33897470Tan J, McKenzie C, Potamitis M, Thorburn AN, Mackay CR, Macia L. The role of short-chain fatty acids in health and disease. Adv Immunol. 2014;121:91-119. doi: 10.1016/B978-0-12-800100-4.00003-9.
PubMed 24388214Kaczmarczyk MM, Miller MJ, Freund GG. The health benefits of dietary fiber: beyond the usual suspects of type 2 diabetes mellitus, cardiovascular disease and colon cancer. Metabolism. 2012 Aug;61(8):1058-66. doi: 10.1016/j.metabol.2012.01.017. Epub 2012 Mar 7.
PubMed 22401879Olopade FA, Norman A, Blake P, Dearnaley DP, Harrington KJ, Khoo V, Tait D, Hackett C, Andreyev HJ. A modified Inflammatory Bowel Disease questionnaire and the Vaizey Incontinence questionnaire are simple ways to identify patients with significant gastrointestinal symptoms after pelvic radiotherapy. Br J Cancer. 2005 May 9;92(9):1663-70. doi: 10.1038/sj.bjc.6602552.
PubMed 15856043Gopalakrishnan V, Helmink BA, Spencer CN, Reuben A, Wargo JA. The Influence of the Gut Microbiome on Cancer, Immunity, and Cancer Immunotherapy. Cancer Cell. 2018 Apr 9;33(4):570-580. doi: 10.1016/j.ccell.2018.03.015.
PubMed 29634945Reis Ferreira M, Andreyev HJN, Mohammed K, Truelove L, Gowan SM, Li J, Gulliford SL, Marchesi JR, Dearnaley DP. Microbiota- and Radiotherapy-Induced Gastrointestinal Side-Effects (MARS) Study: A Large Pilot Study of the Microbiome in Acute and Late-Radiation Enteropathy. Clin Cancer Res. 2019 Nov 1;25(21):6487-6500. doi: 10.1158/1078-0432.CCR-19-0960. Epub 2019 Jul 25.
PubMed 31345839Ogata M, Ogita T, Tari H, Arakawa T, Suzuki T. Supplemental psyllium fibre regulates the intestinal barrier and inflammation in normal and colitic mice. Br J Nutr. 2017 Nov;118(9):661-672. doi: 10.1017/S0007114517002586.
PubMed 29185927Llewellyn SR, Britton GJ, Contijoch EJ, Vennaro OH, Mortha A, Colombel JF, Grinspan A, Clemente JC, Merad M, Faith JJ. Interactions Between Diet and the Intestinal Microbiota Alter Intestinal Permeability and Colitis Severity in Mice. Gastroenterology. 2018 Mar;154(4):1037-1046.e2. doi: 10.1053/j.gastro.2017.11.030. Epub 2017 Nov 23.
PubMed 29174952Ramirez-Farias C, Slezak K, Fuller Z, Duncan A, Holtrop G, Louis P. Effect of inulin on the human gut microbiota: stimulation of Bifidobacterium adolescentis and Faecalibacterium prausnitzii. Br J Nutr. 2009 Feb;101(4):541-50. doi: 10.1017/S0007114508019880. Epub 2008 Jul 1.
PubMed 18590586Sivan A, Corrales L, Hubert N, Williams JB, Aquino-Michaels K, Earley ZM, Benyamin FW, Lei YM, Jabri B, Alegre ML, Chang EB, Gajewski TF. Commensal Bifidobacterium promotes antitumor immunity and facilitates anti-PD-L1 efficacy. Science. 2015 Nov 27;350(6264):1084-9. doi: 10.1126/science.aac4255. Epub 2015 Nov 5.
PubMed 26541606Then CK, Paillas S, Wang X, Hampson A, Kiltie AE. Association of Bacteroides acidifaciens relative abundance with high-fibre diet-associated radiosensitisation. BMC Biol. 2020 Aug 19;18(1):102. doi: 10.1186/s12915-020-00836-x.
PubMed 32811478Walker AW, Ince J, Duncan SH, Webster LM, Holtrop G, Ze X, Brown D, Stares MD, Scott P, Bergerat A, Louis P, McIntosh F, Johnstone AM, Lobley GE, Parkhill J, Flint HJ. Dominant and diet-responsive groups of bacteria within the human colonic microbiota. ISME J. 2011 Feb;5(2):220-30. doi: 10.1038/ismej.2010.118. Epub 2010 Aug 5.
PubMed 20686513
Study at a glance
From the registry record, last updated by the sponsor on 12 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Exploring Mechanism of Action of Dietary Fibre on the Gut Microbiota and Metabolites: Can we Identify Responders and Non-responders to Psyllium and Inulin Dietary Fibres?
- ClinicalTrials.gov ID
- NCT05906589
- Acronym / sponsor ID
- MERLIN / 501
- Keywords
- Dietary fibre, Dietary fiber, Gut microbiota
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 40 participants (actual)
- Lead sponsor
- University of AberdeenUniversity, hospital or other
- Study start
- 7 Sep 2023 (actual)
- Primary completion
- 10 Jul 2025 (actual)
- Study completion
- 10 Jul 2025 (actual)
- First posted
- 18 Jun 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Cancer patients receiving pelvic radiotherapy suffer side effects to the intestine, including diarrhoea and occasionally rectal bleeding, often worsened by chemoradiation. Many pelvic radiotherapy patients receive a form of dietary fibre, psyllium husk, to manage their diarrhoeal symptoms. There is evidence in mice that dietary fibre supplementation can improve tumour response and reduce normal tissue side effects caused by radiation. If this were to be confirmed in humans, it would be a major advance in patient treatment. The investigators will conduct a study in healthy subjects to assess mechanisms and response to dietary fibre.
The investigators will conduct a within-subject diet intervention study on healthy older adults (>60 years old) to determine if a subset of the population are responders to dietary fibre manipulation, using inulin with or without psyllium. This will allow assessment of the physiological impact of dietary fibre. Participants will receive placebo, inulin, or psyllium plus inulin in random order (6 possible combinations) for two weeks each with two-week washout periods.
Baseline faecal microbial activity, short chain fatty acid (SCFA) concentrations, and habitual fibre intake, determined by dietary questionnaires/food diaries will be used to identify individuals in whom dietary fibre manipulation might have a positive impact. Individuals who respond to dietary fibre supplementation may be found to have elevated levels of some SCFAs and significantly increased relative abundance of certain microbiota. Dietary parameters, bacterial relative abundance and SCFA levels will be correlated with plasma cytokine levels.
Detailed description
Of all patients receiving radiotherapy for cancer in 2018 and 2019, 28.6% were treated for a pelvic malignancy. The dose of radiotherapy necessary to cure the tumour often causes side effects in the surrounding healthy tissues, which can significantly impact the patients quality of life. Chemoradiation, the addition of chemotherapy to radiotherapy, improves tumour cure rates by radiosensitising the tumour, but at the expense of worsened normal tissue effects. Most patients over 80 years are unable to tolerate chemoradiation. With an aging population, there is an urgent clinical need to find alternatives to chemoradiation.
A difference in the composition and diversity of the gut microbiota has been found in responders versus non-responders to immunotherapy and in patients experiencing different levels of toxicities following radiotherapy. This indicates that the microbiota could be used to predict, prevent, or treat radiation enteropathy. An often-found side effect in pelvic radiotherapy patients is diarrhoea. Many pelvic radiotherapy patients receive a form of dietary fibre, known as psyllium husk (ispaghula husk or FybogelTM) to manage their diarrhoeal symptoms. Dietary fibres like psyllium and inulin are non-digestible carbohydrates found in fruits, vegetables, whole grains and legumes. They are anaerobically fermented by the gut bacteria, producing SCFAs, including acetate, propionate, and butyrate. SCFAs are the main performers in the interplay between diet, microbiota and health, and have anti-inflammatory and also anti-tumorigenic properties.
A high intake of dietary fibre is proven to decrease the risk of type 2 diabetes, colon cancer and cardiovascular disease by reducing the digestion and absorption of macronutrients and decreasing the contact time of carcinogens with the intestinal lumen. There is emerging evidence that the inclusion of dietary fibre supplements in the diet could modify the tumour response to radiotherapy. If confirmed in humans, this would be a major advance in patient treatment.
In a mouse model of colitis, exhibiting similar acute symptoms to those due to radiotherapy, the addition of psyllium in the diet reduced colonic inflammation and protected intestinal tight junctions. This prevented penetration of luminal inflammatory molecules through the gut wall. In a similar model system, psyllium reduced the severity of colitis in C57BL/6 specific pathogen-free and germ-free mice, via microbiota-dependent and independent mechanisms.
Inulin, another dietary fibre, is rapidly fermented in the proximal large intestine. Here, it selectively increases the growth of the butyrate producer Faecalibacterium prausnitzii and Bifidobacterium spp.. Bifidobacteria are associated with anti-tumour effects and augmented dendritic cell function leading to increased Cytotoxic T-cell (CD8+) priming and accumulation in the tumour microenvironment.
The investigators found promising preliminary data in our mouse studies, indicating that psyllium with inulin enhances tumour control. Immunodeficient mice fed a 10% inulin diet had an improved tumour control following 6 gray (Gy) ionising radiation. Immunocompetent mice showed a delayed tumour growth when receiving psyllium plus inulin when compared to a normal or low fibre diet, accompanied by significantly increased tumour infiltration of cytotoxic T cells. Psyllium plus inulin also significantly increased the percentage of intestinal remaining after 14 Gy compared to a low fibre diet or psyllium alone. A psyllium plus inulin diet also modified intestinal immunity, particularly B cells. Furthermore, in mouse bladder cancer cell UPPL 1591-derived allografts, CD8+ (cytotoxic) T cells scored higher for psyllium and psyllium plus inulin than psyllium plus resistant starch. However, compared to humans, inbred mice are genetically more similar and are held in controlled environmental conditions, so humans are likely to demonstrate more variability in response to dietary fibre intervention.
The investigators will study a group of human participants to assess tolerance and responses to inulin and psyllium plus inulin, in terms of intestinal side effects, significant alterations in the microbiota, levels of SCFAs in plasma and faeces, and plasma inflammatory cytokines. The investigators will also investigate whether responders and non-responders within the study can be identified from baseline dietary information and/or microbial activity (based on faecal SCFA measurements), as an individual's current diet will influence their response to dietary fibre modification.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, investigator)
- Number of arms
- 3
- Model description
- The participants will be randomly allocated to one of the 6 different intervention combinations for the supplements ((A) placebo; (B) inulin; (C) psyllium plus inulin) with the same number of participants in each of the combinations. There are 6 possible combinations: * A > B > C * B > A > C * C > B > A * A > C > B * C > A > B * B > C > A
| Arm | Type | Receives |
|---|---|---|
| Inulin | Experimental | Dietary Supplement: InulinThe participant will be asked to administer the provided doses of 8g inulin twice daily. |
| Inulin + psyllium | Experimental | Dietary Supplement: Inulin, Dietary Supplement: PsylliumThe participant will be asked to administer the provided doses of 8g inulin + 3.5g psyllium twice daily. |
| Maltodextrin | Placebo comparator | Dietary Supplement: MaltodextrinThe participant will be asked to administer the provided doses of 8g maltodextrin twice daily. |
Who may qualify
- Ages
- 60 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- >60 years old
Key exclusion criteria (19 listed)
- Oral antibiotic use (within the past 3 months due to impact on gut microbiota).
- Anti-coagulants (Warfarin).
- Carbamazepine (epilepsy)
- Digoxin (heart conditions)
- Mesalazine (gut problems)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| InulinThe participant will take inulin twice daily over a 14 day period. | Dietary supplement | Inulin, Inulin + psyllium |
| PsylliumAlso: Ispaghula huskThe participant will take psyllium twice daily over a 14 day period. | Dietary supplement | Inulin + psyllium |
| MaltodextrinThe participant will take maltodextrin twice daily over a 14 day period. | Dietary supplement | Maltodextrin |
Primary outcome
Microbial composition using 16S sequencing
Time frame: 11 weeks per participant
To explore the effect of inulin and psyllium plus inulin on microbial composition at baseline and after a 14-day intervention.
Short Chain Fatty Acid (SCFA) levels
Time frame: 11 weeks per participant
To explore the effect of inulin and psyllium plus inulin on short chain fatty acid levels at baseline and after a 14-day intervention.
9 secondary outcomes
Tolerability of Inulin defined by questionnaire 'quality of life' and 'gastrointestinal wellbeing'
Time frame: 11 weeks per participant
Tolerability of psyllium defined by questionnaire 'quality of life SF36' and 'gastrointestinal wellbeing'
Time frame: 11 weeks per participant
Rate of habitual fibre intake before and during the intervention
Time frame: 11 weeks per participant
Faecal SCFA concentrations
Time frame: 11 weeks per participant
Elevated plasma SCFAs
Time frame: 11 weeks per participant
A 0.5 log10 change in health-associated Bifidobacterium spp. from baseline
Time frame: 11 weeks per participant
Plasma cytokine IL-6
Time frame: 11 weeks per participant
Plasma cytokine IL-8
Time frame: 11 weeks per participant
Immunoglobulin A (IgA) and calprotectin levels
Time frame: 11 weeks per participant
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 12 Feb 2026.
- Background: PubMed 34563216Wang L, Wang X, Zhang G, Ma Y, Zhang Q, Li Z, Ran J, Hou X, Geng Y, Yang Z, Feng S, Li C, Zhao X. The impact of pelvic radiotherapy on the gut microbiome and its role in radiation-induced diarrhoea: a systematic review. Radiat Oncol. 2021 Sep 25;16(1):187. doi: 10.1186/s13014-021-01899-y.
- Background: PubMed 29462896Bishehsari F, Engen PA, Preite NZ, Tuncil YE, Naqib A, Shaikh M, Rossi M, Wilber S, Green SJ, Hamaker BR, Khazaie K, Voigt RM, Forsyth CB, Keshavarzian A. Dietary Fiber Treatment Corrects the Composition of Gut Microbiota, Promotes SCFA Production, and Suppresses Colon Carcinogenesis. Genes (Basel). 2018 Feb 16;9(2):102. doi: 10.3390/genes9020102.
- Background: PubMed 33897470Carretta MD, Quiroga J, Lopez R, Hidalgo MA, Burgos RA. Participation of Short-Chain Fatty Acids and Their Receptors in Gut Inflammation and Colon Cancer. Front Physiol. 2021 Apr 8;12:662739. doi: 10.3389/fphys.2021.662739. eCollection 2021.
- Background: PubMed 24388214Tan J, McKenzie C, Potamitis M, Thorburn AN, Mackay CR, Macia L. The role of short-chain fatty acids in health and disease. Adv Immunol. 2014;121:91-119. doi: 10.1016/B978-0-12-800100-4.00003-9.
- Background: PubMed 22401879Kaczmarczyk MM, Miller MJ, Freund GG. The health benefits of dietary fiber: beyond the usual suspects of type 2 diabetes mellitus, cardiovascular disease and colon cancer. Metabolism. 2012 Aug;61(8):1058-66. doi: 10.1016/j.metabol.2012.01.017. Epub 2012 Mar 7.
- Results publication: PubMed 15856043Olopade FA, Norman A, Blake P, Dearnaley DP, Harrington KJ, Khoo V, Tait D, Hackett C, Andreyev HJ. A modified Inflammatory Bowel Disease questionnaire and the Vaizey Incontinence questionnaire are simple ways to identify patients with significant gastrointestinal symptoms after pelvic radiotherapy. Br J Cancer. 2005 May 9;92(9):1663-70. doi: 10.1038/sj.bjc.6602552.
- Results publication: PubMed 29634945Gopalakrishnan V, Helmink BA, Spencer CN, Reuben A, Wargo JA. The Influence of the Gut Microbiome on Cancer, Immunity, and Cancer Immunotherapy. Cancer Cell. 2018 Apr 9;33(4):570-580. doi: 10.1016/j.ccell.2018.03.015.
- Results publication: PubMed 31345839Reis Ferreira M, Andreyev HJN, Mohammed K, Truelove L, Gowan SM, Li J, Gulliford SL, Marchesi JR, Dearnaley DP. Microbiota- and Radiotherapy-Induced Gastrointestinal Side-Effects (MARS) Study: A Large Pilot Study of the Microbiome in Acute and Late-Radiation Enteropathy. Clin Cancer Res. 2019 Nov 1;25(21):6487-6500. doi: 10.1158/1078-0432.CCR-19-0960. Epub 2019 Jul 25.
- Results publication: PubMed 29185927Ogata M, Ogita T, Tari H, Arakawa T, Suzuki T. Supplemental psyllium fibre regulates the intestinal barrier and inflammation in normal and colitic mice. Br J Nutr. 2017 Nov;118(9):661-672. doi: 10.1017/S0007114517002586.
- Results publication: PubMed 29174952Llewellyn SR, Britton GJ, Contijoch EJ, Vennaro OH, Mortha A, Colombel JF, Grinspan A, Clemente JC, Merad M, Faith JJ. Interactions Between Diet and the Intestinal Microbiota Alter Intestinal Permeability and Colitis Severity in Mice. Gastroenterology. 2018 Mar;154(4):1037-1046.e2. doi: 10.1053/j.gastro.2017.11.030. Epub 2017 Nov 23.
- Results publication: PubMed 18590586Ramirez-Farias C, Slezak K, Fuller Z, Duncan A, Holtrop G, Louis P. Effect of inulin on the human gut microbiota: stimulation of Bifidobacterium adolescentis and Faecalibacterium prausnitzii. Br J Nutr. 2009 Feb;101(4):541-50. doi: 10.1017/S0007114508019880. Epub 2008 Jul 1.
- Results publication: PubMed 26541606Sivan A, Corrales L, Hubert N, Williams JB, Aquino-Michaels K, Earley ZM, Benyamin FW, Lei YM, Jabri B, Alegre ML, Chang EB, Gajewski TF. Commensal Bifidobacterium promotes antitumor immunity and facilitates anti-PD-L1 efficacy. Science. 2015 Nov 27;350(6264):1084-9. doi: 10.1126/science.aac4255. Epub 2015 Nov 5.
- Individual participant dataSharing planned: No. No.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Anne E Kiltie, Prof principal investigator
University of Aberdeen
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Inulin, Psyllium and Maltodextrin in people with Psyllium and Inulin, run by University of Aberdeen at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 19 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 12 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Microbial composition using 16S sequencing (time frame: 11 weeks per participant). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT05906589, which also lists 14 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 12 Feb 2026.