Indole-3-Carbinol (I3C): Uses, Benefits, Dosage & Safety

Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

What is Indole-3-Carbinol (I3C)?

Indole-3-carbinol (I3C) is a compound formed when cruciferous vegetables like broccoli are chopped or chewed; in the stomach it converts partly to DIM. It is marketed for hormone balance and cell health.

What Indole-3-Carbinol (I3C) is commonly used for

In supplements, Indole-3-Carbinol (I3C) is most often included for women's hormone & thyroid, skin & anti-aging support. It is used as nutritional support, not as a treatment for any medical condition — the distinction matters, because the claims on a sales page are often stronger than the evidence allows.

How Indole-3-Carbinol (I3C) works

I3C and its products are thought to shift oestrogen metabolism toward less active forms and to influence detoxification enzymes, the basis for its hormone- and cell-health marketing.

What the evidence says

Here's an honest snapshot of what published research suggests about Indole-3-Carbinol (I3C) — including where the evidence is limited.

• I3C has interesting laboratory and preliminary human research on oestrogen metabolism and certain cell-health markers, but clinical evidence for disease prevention is limited and it is unstable compared with DIM.
• Study quality and doses vary, and a result seen in research doesn't guarantee the same for any individual — use the sources below to check the current evidence on Indole-3-Carbinol (I3C) rather than relying on marketing claims.

Typical dosage used in studies

Supplement studies have used a range of doses (often around 200–400 mg/day); eating cruciferous vegetables is the food-based route. This is general information from research, not a personal recommendation or a dosing instruction.

Side effects and safety

I3C can affect oestrogen and interact with hormone-sensitive conditions and medications processed by the liver; it is used cautiously and is avoided in pregnancy. High doses may cause balance or digestive effects. As with any supplement, it's sensible to introduce Indole-3-Carbinol (I3C) on its own, use a trusted brand, and stop if you notice any reaction.

Medication interactions and who should avoid Indole-3-Carbinol (I3C)

Sources & further reading

For authoritative background and the current research base on Indole-3-Carbinol (I3C), consult:

• PubMed — search the research on Indole-3-Carbinol (I3C)
• NIH Office of Dietary Supplements
• NCCIH — National Center for Complementary and Integrative Health
• MedlinePlus — drugs, herbs & supplements

Frequently asked questions

Does Indole-3-Carbinol (I3C) actually work?

I3C has interesting laboratory and preliminary human research on oestrogen metabolism and certain cell-health markers, but clinical evidence for disease prevention is limited and it is unstable compared with DIM. As with most supplements, results vary between people and the marketing is often stronger than the evidence — so it's worth checking the research before relying on it.

Is Indole-3-Carbinol (I3C) safe to take?

For most healthy adults at normal doses it's generally well tolerated, but there are real cautions. I3C can affect oestrogen and interact with hormone-sensitive conditions and medications processed by the liver; it is used cautiously and is avoided in pregnancy. High doses may cause balance or digestive effects. If you take medication, are pregnant or breastfeeding, or have a health condition, check with a doctor or pharmacist first.

What is Indole-3-Carbinol (I3C) used for?

In supplements, Indole-3-Carbinol (I3C) is mainly included for women's hormone & thyroid, skin & anti-aging support — as nutritional support, not as a treatment for any medical condition.