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Indole-3-Carbinol (I3C)
Converts to DIM in the stomach, shifting estrogen metabolism toward favorable 2-hydroxy metabolites for hormonal balance.
What the evidence says
Indole-3-Carbinol appears to help in 3 of 3 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2001–2026 with a typical study size of 23 participants.
Based on 33 studies · 2 meta-analyses · 9 RCTs · 780 total participants
Confidence
HighWhat the studies found
By outcome
Indole-3-Carbinol has an evidence score of 7.5/10 — strong evidence based on 33 indexed studies, including 4 meta-analyses. Converts to DIM in the stomach, shifting estrogen metabolism toward favorable 2-hydroxy metabolites for hormonal balance.
The commonly studied dose of Indole-3-Carbinol is 200-400mg daily. Research points to an estimated optimal dose around 400mg, with a minimum effective dose near 200mg. Individual response varies — start low and adjust.
The best time to take Indole-3-Carbinol is with meals. Take it with food. Indole-3-carbinol (I3C) is an unstable glucosinolate derivative from cruciferous vegetables that requires gastric acid to undergo acid-catalyzed condensation into its active metabolite, diindolylmethane (DIM).
Last reviewed May 2026 · evidence from 40 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Indole-3-Carbinol (I3C) is a compound found in cruciferous vegetables like broccoli, cabbage, and Brussels sprouts. It's converted in the stomach to DIM (diindolylmethane) and other metabolites that influence estrogen metabolism, shifting it toward more favorable 2-hydroxy estrogen metabolites. It's used for hormonal balance, particularly in conditions related to estrogen dominance, and is studied for potential cancer-preventive effects.
Shifts estrogen to favorable metabolites
Converts to DIM in stomach
Induces detoxification enzymes
How Indole-3-Carbinol works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
200-400mg daily
Loading: Not required
Take with food
| Form | Type |
|---|---|
| 💊I3C capsules or DIM (more stable) | Recommended |
| 💊DIM (diindolylmethane) - the active metabolite | Alternative |
I3C must be converted in stomach; DIM is the active metabolite and may be more predictable. Some use both.
Minimum: 4 weeks
Optimal: 12 weeks
Cycling: Not required
Note: Taking with food improves tolerance and allows acid conversion to DIM. Some prefer DIM directly for more predictable metabolism.
Based on single crossover RCT (n=148) showing significant improvement in 2-OHE1:16α-OHE1 ratio with I3C-containing supplement. Conservative estimates due to limited dose-response data and small study population. GI upset is primary dose-limiting side effect.
Improved estrogen metabolism ratio
May reduce estrogen-related symptoms
Enhanced liver detoxification
Can cause digestive upset
Consult doctor; may help but needs monitoring
May increase metabolism of some drugs
May affect hormone therapy; consult doctor
Tip: Take with food; consider DIM instead
Tip: Discontinue if occurs
Indole-3-Carbinol is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are GI upset, skin rash. Use caution if any of these apply to you: Hormone-sensitive conditions (consult doctor); CYP450-metabolized medications.
DIM
Likely helpsShifts estrogen metabolism toward beneficial 2-hydroxy metabolites, reducing harmful estrogen dominance in both men and women.
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