Short Chain Fatty Acids Concentration in StoolsVitaGutNCT07388121
The Effect of Vitamin C Supplementation on Gut Microbiota Composition and Function in Healthy Adults
A study testing Moderate Vitamin C dose (200 mg), High-dose vitamin C supplementation (1000 mg) and Habitual diet (run in period) in people with Short Chain Fatty Acids Concentration in Stools and Gut Microbiota Diversity and Composition, run by University of Glasgow at 1 site in United Kingdom.
Trial summary
The aim of this dietary intervention study is to explore how vitamin C affects the bacteria that live in our gut. Vitamins are essential nutrients found in fruits and vegetables. Our bodies cannot make them on their own, but we need them to function correctly. Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Short Chain Fatty Acids Concentration in Stools, Gut Microbiota Diversity and Composition
- What is being tested?
- Moderate Vitamin C dose (200 mg), High-dose vitamin C supplementation (1000 mg) and Habitual diet (run in period)
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 23 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 1 Nov 2025to 1 Jul 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
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 18 to 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Healthy individuals aged 18-65 years with a BMI between 18.5-35 Kg/m2
- Self-reported good health with no chronic conditions requiring regular medical care
- Willing to provide blood, urine, and stool samples at multiple time points
Who cannot join
- Aged <18 or >65 years
- Smoking
- Chronic illness requiring regular medication or GP visits
- Current or recent medication affecting gut transit or digestion
- Major gastrointestinal surgery
- Pregnant or breastfeeding
Show all 10Show fewer
- Regular use of pre/probiotics, vitamins, or minerals (unless willing to discontinue 2-4 weeks prior)
- Antibiotics in past 3 months
- Weight change >±2 kg in past month
- Participation in other research likely to interfere with this study
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United Kingdom1 site, 1 recruiting
- Recruiting
New Lister Building, Glasgow Royal Infirmary, 10-16 Alexandra Parade, G31 2ER
Glasgow, G31 2ER
Athanasios Koutsos Lecturer in Human Nutrition, PhD, Athanasios.Koutsos@glasgow.ac.uk
Athanasios Koutsos, PhD
About this study
Official title: The Effect of Vitamin C Supplementation on Gut Microbiota Composition and Metabolic Activity in Healthy Adults
The aim of this dietary intervention study is to explore how vitamin C affects the bacteria that live in our gut. Vitamins are essential nutrients found in fruits and vegetables. Our bodies cannot make them on their own, but we need them to function correctly. Vitamins play various roles, including supporting the immune system and assisting with energy production. Some vitamins in our diet can reach the large intestine, where they may be used by gut bacteria to promote their growth. In this study, we aim to investigate how our gut bacteria interact with vitamin C and how this interaction affects their growth and activity.
For this study, participants will follow their habitual diet for one-week (run-in period), followed by two consecutive two-week supplementation periods in which they will first take a moderate dose (200 mg/day) and then a high-dose (1000 mg/day) of vitamin C. A final one-week period follow up period will involve a return to their habitual diet. Faecal, blood and urine samples will be collected at the start and end of each supplementation period to explore changes in gut microbiota composition, activity and markers of inflammation.
Read the detailed description
This is a sequential dietary intervention trial exploring the effects of two doses of vitamin C supplementation on gut microbiota: a moderate, diet-achievable dose of 200 mg/day, and a high dose of 1000 mg/day, each given for two weeks. Primary outcomes will be gut microbiota activity (SCFA production) and composition while secondary exploratory outcomes will include systemic inflammation and gut barrier integrity markers. We anticipate that this pilot study will provide valuable insights into the dose-response effects of vitamin C and help define optimal intakes for promoting gut health.
Twenty-three healthy adults will be recruited from the Glasgow area, with all study visits taking place at the New Lister Building, University of Glasgow. Each participant will attend four study visits over six weeks.
The intervention includes:
- One-week run-in period (habitual diet)
- Two weeks of moderate-dose vitamin C (Vitamin C Chewable Tablet 200 mg, one tablet per day)
- Two weeks of high-dose vitamin C (Vitamin C Chewable Tablet 1000 mg, one tablet per day)
- One-week follow-up (habitual diet)
There will be no washout period between the study periods and participants will be instructed to maintain their usual diet and lifestyle throughout the trial.
Hypothesis Vitamin C supplementation will increase stool SCFAs, particularly butyrate, and beneficially modulate gut microbiota composition, systemic inflammation and gut barrier integrity in healthy adults.
Study schedule and sample collection:
- Visit 1 (Week 0): Baseline anthropometric measurements will be taken (height, weight, body composition); stool and urine sample collection will be arranged. Participants will follow habitual diet for one week (run-in period).
- Visit 2 (Week 1): Anthropometric measurements; stool sample, and fasted blood and urine samples will be collected. The participants will begin a moderate-dose vitamin C supplementation (Vitamin C Chewable Tablet 200mg, one tablet per day) for two weeks (moderate-dose period), in addition to their usual diet.
- Visit 3 (Week 3): Anthropometric measurements; stool sample, and fasted blood and urine samples will be collected. The participants will switch to a high-dose vitamin C supplementation (Vitamin C Chewable Tablet 1000mg, one tablet per day) for two weeks (high-dose period), in addition to their usual diet.
- Visit 4 (Week 5): Anthropometrics; stool sample, and fasted blood and urine samples will be collected. Participants will resume their habitual diet for one week (follow-up period).
- Follow up (Week 6): Final stool sample collected.
Three-day food diaries, Gastrointestinal Symptoms Rating Scale (GSRS) diary, and compliance tick sheets will be completed during the run-in, moderate-dose, and high-dose periods.
Sample size The sample size is based on anticipated effects on stool butyrate, a key SCFA expected to be modified by the intervention. Based on literature and our group's previous results, recruiting 20 healthy participants would provide 80% power (P=0.05) to detect a mean change of 4 μmol/g in stool butyrate (SD: 4.5 μmol/g). Allowing for 15% drop-out, a total of 23 participants will ensure adequate power.
- Being tested
- Moderate Vitamin C dose (200 mg), High-dose vitamin C supplementation (1000 mg), Habitual diet (run in period)
- Keywords
- vitamin C, gut microbiota, SCFA
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Moderate Vitamin C dose (200 mg)Dietary supplement
200 mg of vitamin C provided as a chewable tablet, taken orally daily for two weeks
High-dose vitamin C supplementation (1000 mg)Dietary supplement
1000 mg of Vitamin C provided as a chewable tablet, taken orally daily for two weeks
Habitual diet (run in period)Other
this is a run-in period where participants consume their habitual diet for one week
| Study group | Role | What they receive |
|---|---|---|
| Sequential vitamin C intervention | Experimental | In this single-arm, sequential dietary intervention study, participants will follow their normal habitual diet for one week (run-in period) and then receive two different doses of vitamin C tablets over two consecutive 14-day periods: a moderate dose of 200 mg/day during the first period (2 weeks) and a high dose of 1000 mg/day during the second period (another 2 weeks). The study also includes one week post intervention follow up period (habitual diet) after the high vitamin C dose where participants return to their habitual diet without vitamin C supplementation Receives: Dietary Supplement: Moderate Vitamin C dose (200 mg); Dietary Supplement: High-dose vitamin C supplementation (1000 mg); Other: Habitual diet (run in period) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Butyrate (Short Chain Fatty Acid)
Quantified in stool samples using Gas Chromatography
Measured: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Short Chain Fatty Acids i.e. acetate, propionate, butyrate, total
Quantified in stool samples using Gas Chromatography
Measured: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Stool microbiota composition analysis
16S rRNA gene amplicon sequencing from faecal DNA extracts
Measured: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Secondary outcomes (3)
Stool pH
pH meter
Measured: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Vitamin C in plasma
Using validated analytical techniques
Measured: Week 1 (Visit 2), Week 3 (Visit 3), and Week 5 (Visit 4)
Inflammatory markers
Using Elisa or multiplex assays
Measured: Week 1 (Visit 2), Week 3 (Visit 3), and Week 5 (Visit 4)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Feb 2026
- Study start1 Nov 2025
- Primary completion1 Jul 2026 (estimated)
- Study completion1 Jul 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Short Chain Fatty Acids Concentration in StoolsStudies 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
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Enrolment
- 23 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Glasgow
- Sponsor type
- University, hospital or other
- Collaborators
- Professor Konstantinos Gerasimidis, University of Glasgow
- Responsible party
- Principal investigator, Athanasios Koutsos, University of Glasgow
- Investigators
- Athanasios Koutsos, PhD, Principal investigator, Human Nutrition, School of Medicine, College of Medical, Veterinary, and Life Sciences, University of Glasgow
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07388121
- Sponsor's protocol ID
- 200250024
- Acronym
- VitaGut
- Status last verified
- Nov 2025
- First submitted
- 18 Dec 2025
- Last updated
- 4 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 4 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effect of Vitamin C Supplementation on Gut Microbiota Composition and Metabolic Activity in Healthy Adults
- ClinicalTrials.gov ID
- NCT07388121
- Acronym / sponsor ID
- VitaGut / 200250024
- Keywords
- vitamin C, gut microbiota, SCFA
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 23 participants (estimated)
- Lead sponsor
- University of GlasgowUniversity, hospital or other
- Collaborators
- Professor Konstantinos Gerasimidis, University of Glasgow
- Study start
- 1 Nov 2025 (actual)
- Primary completion
- 1 Jul 2026 (estimated)
- Study completion
- 1 Jul 2026 (estimated)
- First posted
- 4 Feb 2026 (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.
The aim of this dietary intervention study is to explore how vitamin C affects the bacteria that live in our gut. Vitamins are essential nutrients found in fruits and vegetables. Our bodies cannot make them on their own, but we need them to function correctly. Vitamins play various roles, including supporting the immune system and assisting with energy production. Some vitamins in our diet can reach the large intestine, where they may be used by gut bacteria to promote their growth. In this study, we aim to investigate how our gut bacteria interact with vitamin C and how this interaction affects their growth and activity.
For this study, participants will follow their habitual diet for one-week (run-in period), followed by two consecutive two-week supplementation periods in which they will first take a moderate dose (200 mg/day) and then a high-dose (1000 mg/day) of vitamin C. A final one-week period follow up period will involve a return to their habitual diet. Faecal, blood and urine samples will be collected at the start and end of each supplementation period to explore changes in gut microbiota composition, activity and markers of inflammation.
Detailed description
This is a sequential dietary intervention trial exploring the effects of two doses of vitamin C supplementation on gut microbiota: a moderate, diet-achievable dose of 200 mg/day, and a high dose of 1000 mg/day, each given for two weeks. Primary outcomes will be gut microbiota activity (SCFA production) and composition while secondary exploratory outcomes will include systemic inflammation and gut barrier integrity markers. We anticipate that this pilot study will provide valuable insights into the dose-response effects of vitamin C and help define optimal intakes for promoting gut health.
Twenty-three healthy adults will be recruited from the Glasgow area, with all study visits taking place at the New Lister Building, University of Glasgow. Each participant will attend four study visits over six weeks.
The intervention includes:
- One-week run-in period (habitual diet)
- Two weeks of moderate-dose vitamin C (Vitamin C Chewable Tablet 200 mg, one tablet per day)
- Two weeks of high-dose vitamin C (Vitamin C Chewable Tablet 1000 mg, one tablet per day)
- One-week follow-up (habitual diet)
There will be no washout period between the study periods and participants will be instructed to maintain their usual diet and lifestyle throughout the trial.
Hypothesis Vitamin C supplementation will increase stool SCFAs, particularly butyrate, and beneficially modulate gut microbiota composition, systemic inflammation and gut barrier integrity in healthy adults.
Study schedule and sample collection:
- Visit 1 (Week 0): Baseline anthropometric measurements will be taken (height, weight, body composition); stool and urine sample collection will be arranged. Participants will follow habitual diet for one week (run-in period).
- Visit 2 (Week 1): Anthropometric measurements; stool sample, and fasted blood and urine samples will be collected. The participants will begin a moderate-dose vitamin C supplementation (Vitamin C Chewable Tablet 200mg, one tablet per day) for two weeks (moderate-dose period), in addition to their usual diet.
- Visit 3 (Week 3): Anthropometric measurements; stool sample, and fasted blood and urine samples will be collected. The participants will switch to a high-dose vitamin C supplementation (Vitamin C Chewable Tablet 1000mg, one tablet per day) for two weeks (high-dose period), in addition to their usual diet.
- Visit 4 (Week 5): Anthropometrics; stool sample, and fasted blood and urine samples will be collected. Participants will resume their habitual diet for one week (follow-up period).
- Follow up (Week 6): Final stool sample collected.
Three-day food diaries, Gastrointestinal Symptoms Rating Scale (GSRS) diary, and compliance tick sheets will be completed during the run-in, moderate-dose, and high-dose periods.
Sample size The sample size is based on anticipated effects on stool butyrate, a key SCFA expected to be modified by the intervention. Based on literature and our group's previous results, recruiting 20 healthy participants would provide 80% power (P=0.05) to detect a mean change of 4 μmol/g in stool butyrate (SD: 4.5 μmol/g). Allowing for 15% drop-out, a total of 23 participants will ensure adequate power.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Sequential vitamin C intervention | Experimental | Dietary Supplement: Moderate Vitamin C dose (200 mg), Dietary Supplement: High-dose vitamin C supplementation (1000 mg), Other: Habitual diet (run in period)In this single-arm, sequential dietary intervention study, participants will follow their normal habitual diet for one week (run-in period) and then receive two different doses of vitamin C tablets over two consecutive 14-day periods: a moderate dose of 200 mg/day during the first period (2 weeks) and a high dose of 1000 mg/day during the second period (another 2 weeks). The study also includes one week post intervention follow up period (habitual diet) after the high vitamin C dose where participants return to their habitual diet without vitamin C supplementation |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Healthy individuals aged 18-65 years with a BMI between 18.5-35 Kg/m2
- Self-reported good health with no chronic conditions requiring regular medical care
- Willing to provide blood, urine, and stool samples at multiple time points
Key exclusion criteria (10 listed)
- Aged <18 or >65 years
- Smoking
- Chronic illness requiring regular medication or GP visits
- Current or recent medication affecting gut transit or digestion
- Major gastrointestinal surgery
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 |
|---|---|---|
| Moderate Vitamin C dose (200 mg)200 mg of vitamin C provided as a chewable tablet, taken orally daily for two weeks | Dietary supplement | Sequential vitamin C intervention |
| High-dose vitamin C supplementation (1000 mg)1000 mg of Vitamin C provided as a chewable tablet, taken orally daily for two weeks | Dietary supplement | Sequential vitamin C intervention |
| Habitual diet (run in period)this is a run-in period where participants consume their habitual diet for one week | Other | Sequential vitamin C intervention |
Primary outcome
Butyrate (Short Chain Fatty Acid)
Time frame: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Quantified in stool samples using Gas Chromatography
Short Chain Fatty Acids i.e. acetate, propionate, butyrate, total
Time frame: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Quantified in stool samples using Gas Chromatography
Stool microbiota composition analysis
Time frame: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
16S rRNA gene amplicon sequencing from faecal DNA extracts
3 secondary outcomes
Stool pH
Time frame: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)
Vitamin C in plasma
Time frame: Week 1 (Visit 2), Week 3 (Visit 3), and Week 5 (Visit 4)
Inflammatory markers
Time frame: Week 1 (Visit 2), Week 3 (Visit 3), and Week 5 (Visit 4)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 4 Feb 2026.
- Individual participant dataSharing planned: Undecided
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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.
Athanasios Koutsos, PhD principal investigator
Human Nutrition, School of Medicine, College of Medical, Veterinary, and Life Sciences, University of Glasgow
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Moderate Vitamin C dose (200 mg), High-dose vitamin C supplementation (1000 mg) and Habitual diet (run in period) in people with Short Chain Fatty Acids Concentration in Stools and Gut Microbiota Diversity and Composition, run by University of Glasgow 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 3 inclusion and 10 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: looking for participants now, as of the sponsor's last update on 4 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. 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?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Raihana Halim (07857 725347, 2859495H@student.gla.ac.uk), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Butyrate (Short Chain Fatty Acid) (time frame: Baseline (Visit 1), Week 1 (Visit 2), Week 3 (Visit 3), Week 5 (Visit 4) and Week 6 (Visit 5)). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 4 Feb 2026.