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RecruitingNAINTERVENTIONAL

The Effect of Vitamin C Supplementation on Gut Microbiota Composition and Function in Healthy Adults

This study aims to understand how vitamin C affects the bacteria living in our gut, which play a big role in our health. Healthy adults will take a moderate dose of vitamin C for two weeks, followed by a higher dose for another two weeks. We'll also have them stick to their usual diet at the beginning and end. Throughout the study, we'll collect samples like poo, blood, and wee to see if vitamin C changes the types of bacteria in their gut, how well they work, and other health markers. The goal is to learn more about how vitamin C might boost gut health.

At a glance

Status
Recruiting
Phase
NA
Sponsor
University of Glasgow
Enrolment target
23
Start
01 Nov 2025
Estimated completion
01 Jul 2026

What is this study about?

Vitamins are really important nutrients found in foods like fruits and vegetables. Our bodies can't make them, but we need them for everything from fighting off bugs to making energy. Some of these vitamins travel all the way to our large intestine, where they can be used by the many tiny bacteria that live there – these are often called our 'gut bugs' or 'gut microbiota'.

This study wants to find out more about how vitamin C specifically interacts with these gut bugs. We're interested in whether different amounts of vitamin C can change the types of bacteria living in your gut, and how well they produce helpful substances like 'short-chain fatty acids' (SCFAs), which are important for gut health. We'll also look at whether vitamin C affects general body inflammation, which is how your body reacts to injury or infection.

By taking part, you'd be helping us learn whether taking vitamin C supplements could be a simple way to improve the health of our gut bacteria. This research could give us important clues about how much vitamin C might be best for encouraging a healthy gut.

Key takeaways

  • Investigating how vitamin C affects gut bacteria.
  • Healthy adults aged 18-65 needed.
  • Study involves taking moderate then high doses of vitamin C.
  • Requires 4 visits over 6 weeks to the University of Glasgow.
  • Poo, blood, and wee samples will be collected.
  • Aims to understand vitamin C's role in gut health.

Who may be eligible?

To join this study, you need to be a healthy adult aged between 18 and 65 years old. Your Body Mass Index (BMI) should be between 18.5 and 35, which is a measure of your weight in relation to your height. You should also not have any ongoing health problems that need regular medical care and be happy to provide poo, blood, and wee samples several times during the study.

There are some reasons why you might not be able to take part. For example, if you smoke, are pregnant or breastfeeding, or have certain long-term illnesses. If you've had major stomach or bowel surgery, or taken antibiotics recently (in the last 3 months), you also wouldn't be able to join. We also can't include people who regularly take other supplements like prebiotics, probiotics, or other vitamins and minerals, unless they are willing to stop taking them for a few weeks before the study starts.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

  1. Are you between 18 and 65 years old?
  2. Are you generally healthy with no long-term illnesses?
  3. Are you able to visit the University of Glasgow for appointments?
  4. Are you happy to provide poo, blood, and wee samples?
  5. Have you *not* taken antibiotics in the last 3 months?
  6. Are you *not* pregnant or breastfeeding?
Answer every question to see your result.

What does participation involve?

If you join the study, it will last about six weeks in total. In the first week, you'll eat your normal diet. Then, for two weeks, you'll take a moderate dose of vitamin C (200 mg tablet once a day). After that, you'll switch to a higher dose of vitamin C (1000 mg tablet once a day) for another two weeks. Finally, you'll go back to your normal diet for one more week.

You'll need to visit the New Lister Building at the University of Glasgow four times over these six weeks. At each visit, we'll measure your height, weight, and body composition. We'll also ask you to provide poo, blood (taken by a needle from your arm), and wee samples. You'll be asked to keep your normal diet and lifestyle as much as possible throughout the study, and there will be no break when you stop taking the vitamin C between the doses – you'll just switch straight from the moderate to the high dose.

Potential risks and benefits

Taking part in this study could help us understand more about how vitamin C affects gut health, which might benefit future research and public health. For you personally, there are no direct health benefits guaranteed, but you will receive chewable vitamin C tablets known to be safe at these doses. Potential risks are generally low, mainly related to blood tests (like slight bruising or discomfort) and the inconvenience of providing samples. Remember, you can stop participating at any time without giving a reason.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.
  • New Lister Building, Glasgow Royal Infirmary, 10-16 Alexandra Parade, G31 2ER
    Verified postcode
    Glasgow, United Kingdom· Recruiting

Common questions

What are 'gut microbiota'?

These are the trillions of tiny bacteria and other living things that live in your intestines, playing a big role in your health and digestion.

What are 'short chain fatty acids' (SCFAs)?

These are helpful substances produced by your gut bacteria when they break down food, and they're important for the health of your gut lining.

Will I know my own results?

The study aims to understand general trends, and individual results cannot usually be provided for research studies like this one.

Do I need to change my diet for the study?

No, you'll be asked to stick to your usual diet and lifestyle throughout the study, except for taking the vitamin C supplements as instructed.

Where does the study take place?

All study visits will happen at the New Lister Building, University of Glasgow.

How to find out more

Raihana Halim

Always speak to your GP or specialist before deciding to take part in a study.

Interested in taking part?

Register your interest

Share your details and the research team for "The Effect of Vitamin C Supplementation on Gut Microbiota Co…" will contact you if you may be eligible. Always speak to your GP before agreeing to take part.

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