Phytonutrient
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I3C from cruciferous vegetables promotes healthy estrogen metabolism by upregulating CYP1A1 enzymes that favor 2-hydroxylation of estrogens. Clinical doses of 200-400mg daily have been shown to improve estrogen metabolite ratios in human studies. I3C is the precursor to DIM, though its conversion in the stomach produces variable metabolite profiles.
I3C has been studied for estrogen metabolism modulation since the early 1990s. Bradlow et al. first demonstrated its ability to shift estrogen metabolism toward 2-hydroxylation. A notable pilot study by Bell et al. (2000) in Gynecologic Oncology showed 50% regression of CIN 2-3 at 200-400mg daily over 12 weeks. However, the variable metabolite profile created during gastric acid conversion has led many practitioners to recommend DIM as a more predictable alternative.
I3C has been studied for estrogen metabolism modulation since the early 1990s.
| Form | Bioavailability | Best For |
|---|---|---|
| I3C Capsules | Moderate (pH-dependent conversion) | General hormonal support — most common supplemental form |
| I3C + DIM Combination | Moderate-High | Comprehensive estrogen metabolism support — covers both precursor and active metabolite |
General recommendation: 200-400mg daily in divided doses
Timing: Divided into two doses with meals • Take with food for best absorption.
| Condition | Recommended Dose | Evidence |
|---|---|---|
| Estrogen metabolism | 200-400mg daily | Moderate |
| Cervical dysplasia support | 200-400mg daily | Emerging |
| General detoxification | 200mg daily | Preliminary |
Upper limit: 400mg daily (higher doses increase GI side effects)
Safety profile: Generally Safe
DIM is generally preferred for targeted estrogen metabolism support because it provides the primary active metabolite directly, with more predictable dosing and fewer GI side effects. I3C may be preferred when broader Phase I/II detoxification enzyme induction is desired, as it produces a wider range of metabolites beyond just DIM. Some practitioners recommend a combination of both.
You would need to eat approximately 1-2 pounds of raw cruciferous vegetables daily to obtain 200-400mg of I3C. Cooking reduces I3C content by 30-60%. Supplementation provides a far more practical and consistent dose than dietary intake alone.
Studies up to 12 weeks have shown I3C to be generally safe at doses up to 400mg daily. Long-term safety data beyond 12 weeks is limited. Some theoretical concerns exist about high-dose I3C promoting certain undesirable metabolites in the stomach. Periodic breaks or switching to DIM for long-term use is sometimes recommended by practitioners.