I3C (Indole-3-Carbinol)
The upstream precursor to DIM. Converts to DIM (and a few other compounds) in the stomach. Less efficient than direct DIM but cheaper.
Strong for shifting estrogen metabolite ratios (same mechanism as DIM). Moderate for: cervical dysplasia regression, recurrent respiratory papillomatosis, fibrocystic breasts, BPH support. Effects: 8–12 weeks for hormone metabolites.
I3C is the active compound produced when you damage cruciferous vegetable cells (chewing, chopping, cooking) — myrosinase enzyme converts glucobrassicin into I3C. In the acidic stomach, I3C then condenses into DIM and several other indole compounds. Supplementing I3C delivers a broader profile than DIM alone, but with less predictable conversion. Most clinical research has been on cervical dysplasia, breast cancer prevention, and BPH (men). Generally interchangeable with DIM at the user level — pick one or the other rather than both.
- Form
- Indole-3-Carbinol capsules. Less common than DIM in supplement stores.
- Dose
- 200–400 mg/day. Higher clinical doses (up to 800 mg) used in cervical dysplasia research.
- Timing
- With food. AM typical.
- Schedule
- Daily.
- Side effects
- Generally well-tolerated. GI upset, headache. Rarely transient liver enzyme elevations at high doses.
- Interactions
- Hormonal contraceptives, HRT — can reduce contraceptive efficacy. CYP enzyme substrates — I3C modulates multiple CYP enzymes; significant interactions with tamoxifen, warfarin, certain anti-virals.
- Contraindications
- Pregnancy / breastfeeding. On hormonal contraception. Hormone-sensitive cancers without provider input.
- Lab markers
- Urinary 2:16 estrogen metabolite ratio (DUTCH test). Liver enzymes if running high doses long-term.
- Food sources
- Cruciferous vegetables when chopped or chewed raw — broccoli, cabbage, brussels sprouts, kale, cauliflower, bok choy. Cooking partially destroys the I3C-generating enzyme; some raw cruciferous in the diet preserves the conversion.
Pairs with
Calcium D-Glucarate (downstream estrogen clearance). Sulforaphane, DIM (related cruciferous compounds — usually pick one of I3C / DIM, not both).
within Hormone precursors & modulators