Indole-3-Carbinol (I3C)
Research reviewed: Up until 03/2026
Indole-3-Carbinol (I3C) (Indole-3-carbinol) is a dietary supplement with 10 published peer-reviewed studies involving 3,203 participants, researched for Oestrogen Metabolism & Hormonal Balance, Cervical Dysplasia & Cervical Cancer, Cancer Prevention & Anti-proliferative Effects and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Oestrogen Metabolism & Hormonal Balance
ModerateCervical Dysplasia & Cervical Cancer
ModerateCancer Prevention & Anti-proliferative Effects
ModerateSystemic Reviews & Mechanisms
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Oestrogen Metabolism & Hormonal Balance
To evaluate I3C supplementation on oestrogen metabolism and urinary 2-OHE1:16alpha-OHE1 ratio.
Study Type
Randomised placebo-controlled trial
Purpose
To evaluate I3C supplementation on oestrogen metabolism and urinary 2-OHE1:16alpha-OHE1 ratio.
Dose
300-400 mg I3C daily
Participants
60 women at elevated breast cancer risk
Duration
8 weeks
Results
I3C significantly increased urinary 2-OHE1:16alpha-OHE1 ratio, shifting oestrogen metabolism toward less genotoxic pathway.
How They Measured It
Urinary oestrogen metabolites by immunoassay (2-OHE1 and 16alpha-OHE1 ratio)
To characterise I3C dose-response on oestrogen metabolite profiles in post-menopausal women.
Study Type
Dose-finding RCT
Purpose
To characterise I3C dose-response on oestrogen metabolite profiles in post-menopausal women.
Dose
100, 200, or 400 mg I3C daily
Participants
57 post-menopausal women
Duration
4 weeks
Results
400 mg/day produced optimal shift in oestrogen metabolites; 200 mg was partially effective; dose-response relationship confirmed.
How They Measured It
24-hour urinary oestrogen fraction analysis by GC-MS
Cervical Dysplasia & Cervical Cancer
To evaluate I3C supplementation for regression of cervical intraepithelial neoplasia (CIN).
Study Type
Randomised placebo-controlled trial
Purpose
To evaluate I3C supplementation for regression of cervical intraepithelial neoplasia (CIN).
Dose
200 or 400 mg I3C daily
Participants
30 women with CIN 2-3
Duration
12 weeks
Results
Complete regression of CIN in 50% of I3C group vs 0% placebo; regression rate dose-dependent.
How They Measured It
Colposcopy, cervical biopsy grading (CIN 1-3)
To evaluate I3C for treatment of recurrent respiratory papillomatosis (HPV-related).
Study Type
Open-label trial
Purpose
To evaluate I3C for treatment of recurrent respiratory papillomatosis (HPV-related).
Dose
400 mg I3C daily
Participants
18 patients with recurrent respiratory papillomatosis
Duration
8-12 months
Results
Reduced papilloma growth rate and surgical intervention frequency in 72% of patients; HPV E6/E7 expression decreased.
How They Measured It
Endoscopic laryngoscopy, papilloma scoring, HPV viral load
Cancer Prevention & Anti-proliferative Effects
To investigate I3C-induced cell cycle arrest and apoptosis in breast cancer cells.
Study Type
In vitro mechanistic study
Purpose
To investigate I3C-induced cell cycle arrest and apoptosis in breast cancer cells.
Dose
10-100 µM I3C
Participants
MCF-7 and MDA-MB-231 breast cancer cells
Duration
48-72 hours
Results
I3C caused G1 cell cycle arrest, downregulated CDK6 and cyclin D1, and induced apoptosis in both ER+ and ER- breast cancer cell lines.
How They Measured It
Cell cycle analysis by flow cytometry; caspase-3/7 activation; Western blot (CDK6, cyclin D1)
To assess I3C chemoprevention of mammary tumorigenesis in a BRCA1-deficient mouse model.
Study Type
Animal study
Purpose
To assess I3C chemoprevention of mammary tumorigenesis in a BRCA1-deficient mouse model.
Dose
250 ppm I3C in diet
Participants
BRCA1+/- mice
Duration
6 months
Results
I3C significantly reduced mammary tumour incidence by 70% and delayed tumour onset; restored BRCA1 expression in ductal epithelium.
How They Measured It
Tumour incidence, latency, multiplicity; BRCA1 expression
To assess I3C safety and pharmacokinetics and its conversion to DIM in humans.
Study Type
Phase I/II clinical trial
Purpose
To assess I3C safety and pharmacokinetics and its conversion to DIM in humans.
Dose
400-800 mg I3C daily
Participants
30 healthy volunteers
Duration
4 weeks
Results
I3C was rapidly converted to DIM in gastric acid; well tolerated; plasma DIM levels sustained with repeated dosing.
How They Measured It
Plasma I3C and DIM by HPLC; adverse event monitoring
Systemic Reviews & Mechanisms
To review the clinical evidence for I3C in cancer prevention and hormonal disorders.
Study Type
Systematic review
Purpose
To review the clinical evidence for I3C in cancer prevention and hormonal disorders.
Dose
Various doses reviewed
Participants
Multiple studies reviewed
Duration
Review
Results
I3C has promising clinical evidence for oestrogen metabolism optimisation, cervical dysplasia, and cancer chemoprevention, with a favourable safety profile.
How They Measured It
Systematic literature synthesis
To elucidate the multiple molecular targets through which I3C exerts anti-cancer effects.
Study Type
Mechanistic review
Purpose
To elucidate the multiple molecular targets through which I3C exerts anti-cancer effects.
Dose
Varied
Participants
Multiple pre-clinical studies
Duration
Review
Results
I3C modulates Akt, NF-kB, Wnt, and oestrogen receptor signalling; exhibits anti-angiogenic and pro-apoptotic properties across multiple cancer types.
How They Measured It
Literature synthesis of cell signalling, apoptosis, and anti-angiogenesis data
To investigate crucifer vegetable intake (as I3C/DIM source) and colorectal cancer risk.
Study Type
Observational cohort
Purpose
To investigate crucifer vegetable intake (as I3C/DIM source) and colorectal cancer risk.
Dose
Dietary I3C from crucifer vegetables (observational)
Participants
3000 colorectal cancer cases in prospective cohort
Duration
8-year follow-up
Results
High cruciferous vegetable intake associated with 25% lower colorectal cancer risk; strongest association in women.
How They Measured It
FFQ dietary assessment; colorectal cancer incidence from registry
Frequently Asked Questions
Common questions about Indole-3-Carbinol (I3C) research
There are currently 10 peer-reviewed studies on Indole-3-Carbinol (I3C) (Indole-3-carbinol), involving 3,203 total participants. Research covers Cancer prevention, Oestrogen metabolism, Cervical health and 1 more areas. The overall evidence strength is rated as Moderate.
The evidence is currently rated as "Moderate Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (6 human studies), and reported outcomes.
Indole-3-Carbinol (I3C) has been researched for: Cancer prevention, Oestrogen metabolism, Cervical health, Anti-inflammatory. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 6 out of 10 studies are human trials. Human trials carry more weight in our evidence scoring system.
