DIM (diindolylmethane) changes estrogen metabolism in human studies, mostly in women. Here is how it works, the 100-300 mg doses studied, the male evidence and cautions.
When you digest cruciferous vegetables, your gut forms DIM (diindolylmethane). Human studies, mostly in women, found that 100 to 300 mg a day moved estrogen metabolism toward 2-hydroxyestrone. No human trial we found shows DIM raising testosterone or easing symptoms in men, and it can raise SHBG, a protein that binds testosterone.
Indole-3-carbinol (I3C) is found in cruciferous vegetables including broccoli, Brussels sprouts and cauliflower, and the gut turns it into DIM (diindolylmethane). At supplement doses, DIM acts on liver enzymes that help break down estrogen.
Estrogen goes through several pathways in the liver. Two of the metabolites that result are 2-hydroxyestrone, often called the more favorable one, and 16ฮฑ-hydroxyestrone. Human studies, mostly in women, found DIM raised the ratio of 2-hydroxyestrone to 16ฮฑ-hydroxyestrone. Nobody has established whether that changes health outcomes.
In men, the aromatase enzyme turns more testosterone into estrogen as age and body fat rise. That is the basis for marketing DIM to men as a way to clear estrogen. We found no human trial showing it raises testosterone or improves symptoms in men, though. The largest DIM trial involved 130 women on tamoxifen taking 150 mg twice daily for a year. In it, DIM raised SHBG, which binds testosterone and can reduce the free fraction, and it lowered levels of active tamoxifen metabolites.
Most human DIM studies used 100 to 300 mg a day, and a higher dose isn't automatically better. A 2008 dose study found single doses up to 200 mg were well tolerated. At 300 mg, side effects such as nausea and headache appeared, and blood levels didn't rise. DIM3X gives 200 mg a day, which falls inside the studied range and matches many rival products.