Remedy Routes
    Compound

    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

    What is indole-3-carbinol?
    A compound formed when cruciferous vegetables such as broccoli and cabbage are chopped or chewed. In stomach acid it converts to DIM and related products.
    What is it studied for?
    Oestrogen metabolism - it shifts the balance toward 2-hydroxyestrone. Small studies have examined cervical dysplasia and recurrent respiratory papillomatosis, with preliminary results.
    Should I take I3C or DIM?
    DIM is the more stable downstream product and gives more predictable exposure. I3C conversion depends on stomach acidity and yields a mix of compounds.
    What dose is used?
    Trials generally use 200-400 mg/day. Higher doses have been associated with more side effects and are not better supported.
    Does it prevent cancer?
    No. Population data links cruciferous vegetable intake with lower risk, but supplement trials have not demonstrated prevention, and high-dose animal work shows mixed effects.
    Any interactions?
    It induces CYP1A2, which can lower levels of drugs such as some antipsychotics and theophylline. Avoid in pregnancy and discuss with a prescriber if you take regular medication.

    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

    Benefits & Outcomes

    Estrogen Metabolism Support

    Metabolic
    Mixed evidence
    Preliminary
    Effectiveness 3/5

    Biomarker effect proven; clinical outcomes less certain.

    Health Concerns Addressed

    No linked health concerns yet.

    Supporting Research
    5 studies

    Placebo-controlled trial of indole-3-carbinol in the treatment of CIN

    Score: 6/10
    2000
    rct
    n=30

    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.

    View source

    A phase I study of indole-3-carbinol in women: tolerability and effects on estrogen metabolism

    Score: 6/10
    2005
    rct
    n=20

    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.

    View source

    Effects of indole-3-carbinol on estrogen metabolism and breast density: null findings from a randomised biomarker trial

    Score: 7/10
    2011
    rct
    n=50

    Maskarinec G, Morimoto Y, Novotny R +3 more

    Estrogen metabolite ratios shifted modestly but mammographic density and circulating hormone levels were unchanged.

    View source

    Anticancer properties of indole compounds: mechanism of apoptosis induction and role in chemotherapy

    Score: 6/10
    2010
    systematic_review
    0

    Ahmad A, Sakr WA, Rahman KM

    Human chemoprevention evidence remains limited to small biomarker studies.

    View source

    Indole-3-carbinol for recurrent respiratory papillomatosis: long-term results

    Score: 4/10
    2004
    observational
    n=33

    Rosen CA, Bryson PC

    About one third of patients had cessation of papilloma growth and another third had reduced growth rate.

    View source

    Safety Information

    Pregnancy & Breastfeeding

    Pregnancy: Likely unsafe

    Breastfeeding: Not enough evidence to judge

    Detailed safety information not yet available. Always consult a healthcare provider.

    Dosage Guidelines

    Dosage Used in Studies

    Consult healthcare provider

    Dosing by Goal

    GoalDoseNotes
    Typical200–400 mg daily with foodTrial doses for CIN were 200–400 mg/day for 12 weeks

    Forms Compared

    I3C capsules

    Standard 200–400 mg; unstable, keep refrigerated

    DIM supplements

    Stable downstream metabolite; often preferred for consistency

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    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.