A metabolite of indole-3-carbinol (I3C), a phytochemical found in cruciferous vegetables. DIM affects the way in which estrogens are broken down in the body. Supplementing with DIM increases the proportion of inactive (C-2 hydroxylated) metabolites relative to active, potentially carcinogenic (C-16 hydroxylated) ones. Ultimately, this could help reduce the risk of breast cancer in women. DIM can also inhibit the growth of prostate cancer cells.
DIM is recommended in bodybuilding circles to prevent gynecomastia (gyno, or “bitch tits”), as well as reduce the water retention and puffiness that are signs of excess estrogen.