Diindolylmethane (from Brassica) · supplement
Evidence tier: insufficient
Supports healthy oestrogen metabolism, useful for hormonal acne, PMS, and oestrogen dominance patterns.
DIM is an acid condensation product of indole-3-carbinol, itself derived from glucobrassicin in cruciferous vegetables. It is documented to shift oestrogen metabolism toward the 2-hydroxy pathway and away from the 16-alpha-hydroxy pathway, and that shift is real and measurable in urine. The leap that is NOT established is the one the marketing depends on: that moving this ratio produces any clinical benefit. It has never been shown to. The same enzyme induction that moves the ratio is also the most likely route by which DIM lowers endoxifen, so the mechanism cuts against the user as readily as for them.
Insufficient. DIM is sold for oestrogen dominance, hormonal acne and PMS, and there is no human trial supporting any of those three. What human trials exist were run in DISEASE populations, and the good ones are negative. The largest is a double blind randomised controlled trial in 551 women with low grade cervical cytological abnormalities (British Journal of Cancer 2012): DIM produced no therapeutic effect on cytology, colposcopy or histology. A second randomised trial in 64 women with biopsy proven CIN2 or CIN3 (Del Priore, Gynecologic Oncology) found roughly two thirds of lesions regressed in BOTH arms, with no statistically significant difference between DIM and placebo. MSK About Herbs summarises the whole field as preclinical: anti inflammatory and antiproliferative properties in the laboratory, with human evidence limited to castration resistant prostate cancer signals and altered oestrogen metabolite ratios in postmenopausal women with a history of early stage breast cancer, where MSK notes the implication for breast cancer risk 'remains unclear'. Shifting a urinary metabolite ratio is not a clinical outcome. The one thing DIM demonstrably does in people is the thing nobody wants: a clinical trial found DIM 'resulted in a significant decrease in serum endoxifen', the active metabolite of tamoxifen. DIM measurably weakens tamoxifen. MSK also flags reduced effectiveness of CYP450 and MDR1 substrate drugs, and advises against use in pregnancy, when planning pregnancy, when nursing, or on oral contraceptives.
No regulator sets a dose and no dose has been shown effective for any consumer use. For reference only, the negative trials used 150 mg daily (cervical cytology trial) and 2 mg per kg bodyweight daily (CIN trial).
100 to 200 mg daily with food. Cycle off occasionally.
Avoid in pregnancy. Caution with hormone sensitive cancers and contraceptive medications.
Pregnancy: avoid
Breastfeeding: avoid
Active compounds: 3,3'-diindolylmethane
Remedies using DIM · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.