Indole-3-Carbinol
Indole-3-Carbinol
TL;DR
Cruciferous-vegetable compound that shifts estrogen metabolism toward 2-hydroxylation in human trials. Reasonable mechanistic case for estrogen-dominant patterns, but long-term safety of altered estrogen metabolites is unresolved.
Ideal For
- People with estrogen-dominant patterns working with a clinician
- Those who cannot eat adequate cruciferous vegetables
Avoid If
- Pregnancy or trying to conceive
- Thyroid conditions (goitrogenic potential)
- Hormone-sensitive cancers without oncologist approval
Frequently Asked Questions
Overview
Indole-3-carbinol (I3C) is formed when glucobrassicin in cruciferous vegetables (broccoli, cabbage, kale) is broken down by chewing and stomach acid; in the stomach it condenses into DIM and related oligomers, which are the actual absorbed species. Human trials consistently show I3C induces CYP1A2 and shifts estradiol metabolism toward 2-hydroxyestrone over 16-alpha-hydroxyestrone — a ratio some researchers associate with lower estrogenic activity. Clinical evidence includes a randomized trial in cervical intraepithelial neoplasia (CIN) showing higher regression rates with 200–400 mg/day versus placebo, and smaller studies in cyclic mastalgia. However, the long-term consequences of pharmacologically shifting estrogen metabolism are not fully characterized, and I3C is a goitrogen at high doses in animal models. Eating cruciferous vegetables achieves the same pathway more gently and with a stronger safety record.
How It Works
- Converts to DIM and acid-condensation products in the stomach
- Induces CYP1A2, shifting estradiol toward 2-hydroxyestrone
- Modulates aryl hydrocarbon receptor (AhR) signaling in estrogen-responsive tissues
Health Concerns Addressed
No linked health concerns yet.
Supporting Research5 studies
Placebo-controlled trial of indole-3-carbinol in the treatment of CIN
Bell MC, Crowley-Nowick P, Bradlow HL +7 more
Complete regression of CIN occurred in 4 of 8 patients at 200 mg and 4 of 9 at 400 mg, versus none of 10 in the placebo group.
A phase I study of indole-3-carbinol in women: tolerability and effects on estrogen metabolism
Reed GA, Peterson KS, Smith HJ +5 more
Indole-3-carbinol was well tolerated up to 400 mg twice daily and increased the 2-hydroxyestrone to 16-alpha-hydroxyestrone ratio.
Effects of indole-3-carbinol on estrogen metabolism and breast density: null findings from a randomised biomarker trial
Maskarinec G, Morimoto Y, Novotny R +3 more
Estrogen metabolite ratios shifted modestly but mammographic density and circulating hormone levels were unchanged.
Indole-3-carbinol as a chemopreventive agent: mechanisms, clinical evidence and safety considerations
Ahmad A, Sakr WA, Rahman KM
Human chemoprevention evidence remains limited to small biomarker studies.
Indole-3-carbinol for recurrent respiratory papillomatosis: long-term results
Rosen CA, Bryson PC
About one third of patients had cessation of papilloma growth and another third had reduced growth rate.
Safety Information
Pregnancy & Breastfeeding
Pregnancy: likely_unsafe
Breastfeeding: insufficient_data
Detailed safety information not yet available. Always consult a healthcare provider.
Dosage Guidelines
Dosage Used in Studies
Consult healthcare provider
Forms Compared
Standard 200–400 mg; unstable, keep refrigerated
Stable downstream metabolite; often preferred for consistency
Medical Disclaimer
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Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.