Evidence Level
DIM research has focused on its ability to modulate estrogen metabolism, particularly the 2:16α-OHE1 ratio. Dalessandri et al. (2004) conducted a dose-finding study in postmenopausal women with early-stage breast cancer history, finding that 108mg of enhanced-absorption DIM (BioResponse) daily significantly increased the urinary 2:16α-OHE1 ratio. Thomson et al. (2017) confirmed these findings in a larger trial. The preferential shift toward 2-hydroxylation is considered potentially protective because 2-OHE1 has weak estrogenic activity and may have anti-proliferative properties, while 16α-OHE1 is a potent estrogen metabolite. In vitro and animal studies support anti-cancer mechanisms, but large-scale clinical cancer prevention trials are still needed.