Evidence Level
Indole-3-Carbinol (I3C) is a compound derived from cruciferous vegetables and has been studied for its potential benefits in managing estrogen metabolism, HPV-related conditions, and cancer prevention. Rosen et al. (1998) conducted a study on recurrent respiratory papillomatosis (RRP), where 200mg of I3C daily led to remission or reduced disease progression in 63% of participants, with no worsening of symptoms. Bell et al. (2000) reported that in a randomized, placebo-controlled trial involving 30 women with cervical intraepithelial neoplasia (CIN II-III), I3C at doses of 200 and 400 mg/day significantly increased the rate of complete regression compared to placebo.
In terms of estrogen metabolism, I3C is known to influence the ratio of 2-hydroxyestrone (2-OHE1) to 16α-hydroxyestrone (16α-OHE1), though its effects are less consistent than those of DIM due to pH-dependent conversion kinetics. Reed et al. (2006) found that I3C administration in women resulted in detectable levels of its metabolite, DIM, with increasing doses up to 1,000 mg. However, the field has generally shifted toward recommending DIM over I3C for estrogen modulation due to DIM's more consistent bioavailability and activity as a primary active metabolite (Higdon et al., 2007).