Rhamnogalacturonan-I (carrot RG-I)
Summary
Rhamnogalacturonan-I is a pectin fibre, sold as a carrot extract taken in fractions of a gram a day. In one 177-person rhinovirus challenge trial, 0.3 g/day shortened and eased cold symptoms, but the higher 1.5 g/day dose did not. A second trial of 54 adults raised gut Bifidobacterium. All trials were funded or co-run by the ingredient maker.
Key facts
- 0.3 g/day reduced symptom severity by 20% and duration by 25%; 1.5 g/day results fell between placebo and 0.3 g/day[1]
- 3 graded human outcomes on this page
- October 13, 2026
How it works
ProposedCell and lab studies identified RG-I as the immune-active part of carrot and bell-pepper pectin; it primed innate immune cells and was fermented by gut bacteria. In the challenge trial, nasal interferon and innate immune responses to rhinovirus started sooner. How a fibre that is not absorbed signals to immune cells in the airway is proposed, not established.[5][1][2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Colds | Grade C | Improved | RCT · n = 177 · 2021 | 1 row |
| Gut microbiota | Grade D | Mixed | RCT · n = 146 · 2024 | 2 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Severity and duration of cold symptoms after rhinovirus challenge | Improved | Grade C | RCT · n = 177 · 2021 Healthy adults aged 18–65 challenged with rhinovirus-16 (Netherlands) Form: Carrot-derived RG-I (cRG-I) · Dose: 0.3 g/day or 1.5 g/day · Duration: 8 weeks before challenge, continued during infection At 0.3 g/day, symptom severity fell by 20% and duration by 25%, with faster viral clearance and a faster interferon response. At 1.5 g/day, antiviral responses and symptom scores fell between placebo and 0.3 g/day. | 34959949 (opens PubMed)Source [1] |
| Gut microbiota composition (same challenge trial) | Mixed | Grade D | RCT · n = 146 · 2024 Healthy adults in the rhinovirus challenge trial (placebo 46, 0.3 g/day 49, 1.5 g/day 51) Form: Carrot-derived RG-I (cRG-I) · Dose: 0.3 g/day or 1.5 g/day · Duration: 8 weeks Overall microbiota composition did not change, but Bifidobacterium (mainly B. adolescentis and B. longum) increased at both doses, and microbiota became more stable. Symptom severity did not correlate directly with the microbial changes. | 38593705 (opens PubMed)Source [3] |
| Faecal Bifidobacterium, immune cell activation and stool consistency | Improved | Grade D | RCT · n = 54 · 2025 Healthy adults aged 18–70 (Sweden) Form: Carrot-derived RG-I (cRG-I) · Dose: 500 mg/day · Duration: 4 weeks Faecal Bifidobacterium rose, peaking at week 3; isobutyric acid rose but other short-chain fatty acids did not; more circulating dendritic cells carried activation markers; stool consistency improved slightly. | 41011488 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Carrot-derived RG-I (cRG-I) powder | Varies[1][4] | Not absorbed as such; it is fermented by gut bacteria. No human absorption data.[4][5] | Described as safe and well tolerated at 0.3–1.5 g/day for 8 weeks and 0.5 g/day for 4 weeks.[1][4] | Rhinovirus challenge and gut microbiota trials |
Studied doses
Doses studied in human trials ranged from 300 to 1,500 mg/day of carrot RG-I: 300 or 1,500 mg/day for 8 weeks before a rhinovirus challenge, and 500 mg/day for 4 weeks. The 300 mg/day dose gave the clearest symptom benefit.[1][3][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Medicines
- No interaction studies have been published. As a non-absorbed fibre, it has not been tested alongside antibiotics, immune-suppressing drugs or chemotherapy.[1][4]
- Pregnancy, breastfeeding and children
- The trials enrolled healthy adults only, so there are no safety data for these groups.[1][4]
- Carrot allergy
- The ingredient is made from carrot; the trials did not report on people with carrot allergy.[4]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- More is not betterIn the only infection trial, 0.3 g/day outperformed 1.5 g/day, so a larger dose on a label is not evidence of a stronger effect.[1]
- Carrot RG-I vs generic pectinThe trials used a specific carrot-derived RG-I ingredient; ordinary citrus or apple pectin is a different fibre and was not tested.[1][4]
Cost per studied dose, without the sales pitch
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Cost per studied dose
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Frequently asked questions
What is rhamnogalacturonan-I?
A component of pectin, the soluble fibre in plant cell walls. Supplements use a version extracted from carrots (cRG-I).[5][4]
Does carrot RG-I help with colds?
One trial of 177 adults infected with rhinovirus found milder, shorter symptoms at 0.3 g/day, but not as clearly at 1.5 g/day. It has not been tested against naturally caught colds.[1]
Is it a prebiotic?
It raised gut Bifidobacterium in two trials (0.3–1.5 g/day for 8 weeks and 0.5 g/day for 4 weeks), without changing overall microbiota composition in the larger one.[3][4]
Sources
- [1]The Dietary Intake of Carrot-Derived Rhamnogalacturonan-I Accelerates and Augments the Innate Immune and Anti-Viral Interferon Response to Rhinovirus Infection and Reduces Duration and Severity of Symptoms in Humans in a Randomized Trial.. Nutrients, 2021. RCT
- [2]Effects of Dietary Supplementation with Carrot-Derived Rhamnogalacturonan-I (cRG-I) on Accelerated Protective Immune Responses and Quality of Life in Healthy Volunteers Challenged with Rhinovirus in a Randomized Trial.. Nutrients, 2022. RCT
- [3]The impact of daily supplementation with rhamnogalacturonan-I on the gut microbiota in healthy adults: A randomized controlled trial.. Biomed Pharmacother, 2024. RCT
- [4]Carrot Rhamnogalacturonan-I Supplementation Shapes Gut Microbiota and Immune Responses: A Randomised Trial in Healthy Adults.. Microorganisms, 2025. RCT
- [5]Development of an Affordable, Sustainable and Efficacious Plant-Based Immunomodulatory Food Ingredient Based on Bell Pepper or Carrot RG-I Pectic Polysaccharides.. Nutrients, 2021. RCT
What changed
- Adversarial second pass: every PMID re-checked against NCBI esummary (title, year, no retraction, erratum or expression-of-concern flags) and every number in each evidence row re-read against its PubMed abstract (PMC full text where the abstract lacked dose or duration). Countries and funding notes kept only where the abstract or full text states them; interactions listed only where a source supports them, otherwise stated as unstudied.
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.