DIM wont prevent the aromitization. Its not that kind of estrogen blocker. It helps your body eliminate the "bad" estrogens while preserving the "good" estrogen.
A phytonutrient and plant indole found in cruciferous vegetables including broccoli, brussels sprouts, cabbage, cauliflower and kale, with potential antiandrogenic and antineoplastic activities. As a dimer of indole-3-carbinol, diindolylmethane (DIM) promotes beneficial estrogen metabolism in both sexes by reducing the levels of 16-hydroxy estrogen metabolites and increasing the formation of 2-hydroxy estrogen metabolites, resulting in increased antioxidant activity. Although this agent induces apoptosis in tumor cells in vitro, the exact mechanism by which DIM exhibits its antineoplastic activity in vivo is unknown. Check for active clinical trials using this agent. (NCI Thesaurus)
US brand name: BioResponse DIM
Chemical structure name: 3,3'-diindoylmethane