About I3C
A glucosinolate-derived compound from cruciferous vegetables (broccoli, cabbage) and the dietary precursor to DIM, into which it converts under stomach acid. Studied mainly for estrogen metabolism — shifts the 2-OHE1:16α-OHE1 ratio toward the protective 2-hydroxy pathway in humans (dose-dependent). One small placebo-controlled RCT in cervical intraepithelial neoplasia (Bell 2000, Gynecologic Oncology, n=30) found ~50% biopsy normalization at 200–400 mg/day over 12 weeks vs placebo, with no added benefit at the higher dose. Evidence is limited by very small samples and a lack of large confirmatory trials; I3C-to-DIM conversion is variable, which is why some products use DIM directly. Distinct from the Diindolylmethane (DIM) entry. Not an essential nutrient.
What I3C supports
- Shifts estrogen metabolism toward the protective 2-hydroxy pathway
- Studied for cervical dysplasia (one small RCT)
How much I3C to take
The RDA prevents deficiency. The effective range is what clinical trials used to actually move the outcome.
Effective
200–400
mg
200–400 mg/day used in the CIN RCT; no added benefit observed at 400 vs 200 mg. Common supplement dose 200–400 mg.
Clinical evidence
Limited clinical evidence. One small placebo-controlled RCT in cervical dysplasia (n=30) plus consistent estrogen-metabolite shifts; samples small, no large confirmatory trials
Reference