Diindolylmethane

DIM (3,3'-diindolylmethane) is the primary bioactive metabolite of indole-3-carbinol (I3C), found in cruciferous vegetables (broccoli, cauliflower, cabbage). DIM shifts estrogen metabolism toward the 2-hydroxylation pathway (producing 2-OHE1, a weaker, potentially protective estrogen metabolite) and away from the 16α-hydroxylation pathway (producing 16α-OHE1, a more proliferative metabolite). This 2:16 ratio shift is the primary mechanism of interest for both cancer chemoprevention and TRT estrogen management. In men on TRT, DIM is used as a "natural" estrogen modulator — not an aromatase inhibitor (it doesn't block estrogen production) but a metabolism shifter that redirects estrogen toward less potent metabolites. Clinical trials confirm DIM shifts urinary 2:16-OHE1 ratios in both men and women. It also has anti-androgenic effects at very high doses, so dosing precision matters in TRT contexts. The bioavailability of crystalline DIM is poor; microencapsulated or absorption-enhanced formulations (BioResponse DIM) are standard.