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

Recruiting now · Not applicable

Conditions studied: Short Chain Fatty Acids Concentration in Stools, Gut Microbiota Diversity and Composition

In brief

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.

Key facts

Study ID

NCT07388121

Run by

University of Glasgow

People needed

23

Starts

2025-11-01

Expected to finish

2026-07-01

Last updated by the study team

2026-02-04

Who can join

Age: 18 and older, up to 65. Sex: any. Healthy volunteers: accepted.

You may qualify if…

• 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

You may not qualify if…

• 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
• 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

Where it is running

• New Lister Building, Glasgow Royal Infirmary, 10-16 Alexandra Parade, G31 2ER — Glasgow, United Kingdom (enrolling)

Full record on ClinicalTrials.gov

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