Supplement
Rhamnogalacturonan I is a branched plant fiber found in carrots and citrus that appears to interact with immune cells. In one trial, healthy volunteers exposed to a cold virus had milder cold symptoms and better quality of life after carrot-derived RG-I than after placebo, and their natural killer cell activity went up. The evidence is limited to that single trial, and other immune findings come mostly from animal or lab studies.
Sources: PMID 36296939
- Updated
- How we grade
- 2 studies cited
- Best evidence
- Grade C
- Conditions studied
- 2
- Outcomes
- 5
- Graded outcomes
- 0032
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Cold Symptom Severity A single RCT (n=146) challenged healthy volunteers with rhinovirus-16 after 8 weeks of carrot-derived RG-I supplementation (0.3 or 1.5 g/day). cRG-I significantly reduced WURSS-21 symptom scores (p<0.001) and improved quality of life measures (p<0.01) compared to placebo, with 0.3 g/day showing the strongest effects. | Improves (the measure goes down) | Moderate effect | 1 study | 146 people | ||
General
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| NK Cell Activity In the same rhinovirus challenge RCT (n=146), cRG-I supplementation significantly increased CD107a-positive NK cell degranulation (p<0.001), indicating enhanced natural killer cell cytotoxic activity. Interferon-response gene expression was also upregulated in treated groups. | Improves (the measure goes up) | Moderate effect | 1 study | 146 people | ||
| Macrophage Activation In vitro studies show RG-I activates macrophages via complement system and TLR signaling. A 2025 study in zebrafish and RAW 264.7 macrophages demonstrated that RG-I-enriched pectin dose-dependently enhanced macrophage phagocytosis, upregulated immune genes (TNF-alpha, IL-1beta, NF-kappaB), and restored gut microbiota in immunocompromised animals. No human data for this specific outcome. | Improves (the measure goes up) | Small effect | 1 study | |||
Studies that measured macrophage activation | ||||||
| Cancer Progression Modified Citrus Pectin (containing RG-I) inhibits galectin-3, a protein involved in cancer cell adhesion and metastasis. Preliminary human studies and preclinical data suggest possible benefit as adjunct cancer therapy, but research is early-stage and no well-powered clinical trials exist for this indication. | Changes; see studies | Small effect | ||||
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Heavy Metal Excretion Several human studies using Modified Citrus Pectin (which contains RG-I) have demonstrated increased urinary excretion of lead, arsenic, and cadmium. MCP is used as a gentle chelation therapy, though the contribution of RG-I specifically versus other pectin components is unclear. | Improves (the measure goes up) | Moderate effect |
Key findings
- Cold Symptom SeverityImproves (the measure goes down)
- NK Cell ActivityImproves (the measure goes up)
- Heavy Metal ExcretionImproves (the measure goes up)
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- Grade C
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Studies cited
2 studies from PubMed
- Mild ultrasound-assisted alkali de-esterification modified pectins: Characterization and structure-activity relationships in immunomodulatory effects
- 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