What is Indole-3-Carbinol (I3C)?

Indole-3-carbinol (I3C) is a phytochemical found in cruciferous vegetables such as broccoli, cabbage, and Brussels sprouts. It is also available as a dietary supplement.

What are the potential benefits of I3C?

I3C is commonly used to support estrogen metabolism and hormone balance. It is also studied for cervical health and for its potential role in cancer risk reduction, though evidence varies by condition.

What is a typical I3C dosage?

Common supplemental doses are in the range of 200–400 mg per day. Dosing can depend on the goal and individual factors, so follow product directions and clinician guidance.

Is I3C the same as DIM?

No. I3C can convert in the stomach to several compounds, including diindolylmethane (DIM), which is also sold as a supplement; they are related but not identical.

Who should avoid I3C or use caution?

People who are pregnant or breastfeeding, have hormone-sensitive conditions, or take medications affected by liver enzymes should use caution. Consult a healthcare professional before use, especially if you take prescription drugs.

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Indole-
3-Carbinol

Moderate study situation·7/10

A higher score indicates better study conditions, but not necessarily effectiveness.

A natural compound found in cruciferous vegetables with potential benefits for hormone balance, cervical health, and cancer prevention.

Cancer-inhibitor Immune Booster Liver Health Hormone Balance

dose range

200–400 mg

Divided into 2 doses with meals

Consumption

Take with meals, preferably breakfast and dinner/lunch for best absorption.

Not fat-soluble.

Best time

Dividing doses with meals may help reduce gastrointestinal side effects and improve stability.

Description

Indole-3-carbinol (I3C) is a phytochemical from cruciferous vegetables like broccoli and cabbage; it is used as a supplement for its roles in hormone metabolism, detoxification, and possible cancer risk reduction.

benefits

Main effects with level of evidence

Moderate

Note on evidence

Human and animal studies support benefits for hormone metabolism and cervical health, with preliminary evidence in cancer prevention. More large-scale trials needed.

Potential cancer prevention

Moderate

I3C may promote favorable estrogen metabolism and inhibit tumor growth, particularly in hormone-sensitive cancers such as breast and prostate cancer, according to preclinical and some clinical studies.

Particularly relevant for: adults at risk for hormone-related cancers

1 · PubMed 2 · PubMed 6 · Examine.com

Cervical health and HPV support

Moderate

Clinical studies suggest I3C may aid regression of cervical intraepithelial neoplasia (CIN) and support HPV clearance when used at 200–400 mg daily.

Particularly relevant for: women with HPV or cervical dysplasia

3 · PubMed 6 · Examine.com

Detoxification and liver enzyme support

Limited

I3C induces phase I and II detoxification enzymes in the liver, potentially aiding in the breakdown and removal of toxins and carcinogens.

Particularly relevant for: adults seeking enhanced detoxification

1 · PubMed 5 · NIH ODS Fact Sheet: Cruciferous Vegetables

Safety & Information

Important safety information & known risks

For educational purposes only • not medical advice

Generally well-tolerated at typical doses but may cause gastrointestinal upset or thyroid changes at higher intakes. Use is not recommended during pregnancy or breastfeeding.

warning notices

Common side effects include mild gastrointestinal complaints like nausea or diarrhea.
May affect thyroid function at high doses or in sensitive individuals.
Long-term safety is not fully established; most studies are short-term.
Avoid use during pregnancy or breastfeeding due to potential hormonal effects.
Consult a healthcare provider before use if taking medications metabolized by the liver (CYP450 substrates), including tamoxifen.
Use cautiously or avoid in individuals with thyroid disorders due to potential thyroid function effects at high doses.

Known interactions with medications

Tamoxifen
CYP450-metabolized medications (e.g., warfarin, some antidepressants, statins)

Contraindications / special precautions

Pregnancy or breastfeeding
Active thyroid disorders
Concurrent use with tamoxifen unless supervised

interactions

Important interactions between active ingredient ↔ supplement / medication / food

I3C is metabolized by, and may induce, cytochrome P450 enzymes, altering the effects of drugs processed by these pathways. Possible additive or antagonistic effects with hormone therapies or tamoxifen.