Diindolylmethane

non-nutrient/non-botanical3,3'-diindolylmethane

What is it

Diindolylmethane (3,3'-diindolylmethane, DIM) is a compound formed in the acidic environment of the stomach from indole-3-carbinol (I3C), which is present in cruciferous vegetables. It is marketed as a supplement targeting estrogen metabolism and hormonal balance.

How it works

DIM modulates estrogen metabolism by promoting the formation of 2-hydroxyestrone (considered a less hormonally active metabolite) and reducing the formation of 16-alpha-hydroxyestrone (considered more estrogenically active). This redirection of estrogen metabolism is the mechanistic basis for DIM's purported hormonal support effects. Research suggests DIM also acts on the aryl hydrocarbon receptor (AhR), a transcription factor that regulates phase I detoxification enzymes including CYP1A1, CYP1A2, and CYP1B1. Through AhR signaling, DIM influences a wide range of cellular processes, including immune responses, inflammation, and cell cycle regulation. In preclinical studies, DIM has shown anti-proliferative effects on hormone-sensitive cancer cells, anti-inflammatory activity, and immune-modulating properties. Clinical translation of these findings remains limited, with most human evidence focused on measurable shifts in urinary estrogen metabolite ratios rather than disease endpoints.

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Estrogen metabolism modulation

Grade C

Moderate evidence

Small trials show DIM measurably shifts urinary estrogen metabolite ratios toward the 2-hydroxyestrone pathway. The clinical significance for long-term outcomes remains uncertain.

Cervical dysplasia

Grade D

Mixed evidence

DIM and I3C have been studied for cervical intraepithelial neoplasia management, with mixed results. Not standard of care.

Hormone-related symptoms

Grade F

Limited evidence

Popular use for PMS, hormonal acne, and perimenopausal symptoms is not supported by robust clinical evidence.

Cancer prevention

Grade F

Limited evidence

Mechanistic and preclinical evidence is suggestive but human trials have not demonstrated cancer prevention benefits.

3 commercial forms

BR-DIM (BioResponse DIM)

Phospholipid complex with significantly improved absorption compared to crystalline DIM.

The form used in most clinical research and the recommended option for measurable biological effects.

Crystalline DIM

Very poor absorption; high doses needed for any biological effect.

Less expensive but generally inefficient; enhanced formulations are preferable.

DIM with absorption enhancers

Various adjuncts like vitamin E, lecithin, or piperine added.

Marketed for improved absorption with varying clinical evidence.

Dosage

Typical supplement doses are 100-200 mg per day. Clinical trials have used doses up to 300 mg per day. Bioavailability-enhanced formulations (e.g., BR-DIM) are commonly used since plain crystalline DIM has poor absorption. There is no established RDA.

When and how to take it

Take DIM with food containing fat to enhance absorption. Most users take it once or twice daily. Bioavailability-enhanced formulations such as BR-DIM are preferred over plain crystalline DIM. Consistent use over several weeks to months is needed to evaluate hormonal effects.

Food sources

FoodAmount%DV
Broccoli (1 cup cooked)I3C precursor that converts to DIM in the stomach—
Brussels sprouts (1 cup)Among highest I3C content—
Cabbage, raw (1 cup)Significant I3C—
Kale (1 cup cooked)I3C source—
Bok choy (1 cup)I3C source—

Safety

DIM is generally well tolerated at typical doses. Reported side effects at higher doses include headache, nausea, gastrointestinal upset, and changes in menstrual cycle. A common harmless side effect is bright yellow-orange urine due to DIM metabolite excretion. Long-term safety beyond a year has not been thoroughly studied.

Who should be cautious

Avoid in pregnancy and breastfeeding due to insufficient safety data and potential hormonal effects. People with hormone-sensitive cancers (breast, ovarian, uterine) should consult their oncologist. Women taking hormonal contraceptives or HRT should consult a clinician about possible interactions. People with liver disease should avoid high doses.

Interactions

DIM may affect the metabolism of medications cleared by CYP1A1, CYP1A2, and other induced enzymes, potentially affecting drug levels of certain antidepressants, beta-blockers, theophylline, caffeine, and others. It may interact with hormonal medications including birth control, hormone replacement therapy, and tamoxifen. People taking these medications should consult a clinician.

Frequently asked questions

Should I take DIM or I3C?⌄

DIM is more chemically stable and is the active form many seek. I3C converts to DIM in the stomach but also produces other compounds with variable effects. Most clinical research has shifted toward DIM.

How long until DIM affects my hormones?⌄

Measurable shifts in estrogen metabolite ratios appear within 4-8 weeks of consistent supplementation. Symptom changes, if any, may take longer.

Is bright orange urine on DIM normal?⌄

Yes, this is a common and harmless effect. It indicates the supplement is being absorbed and metabolized.

Can men take DIM?⌄

Yes. Men also benefit from healthy estrogen metabolism. DIM is sometimes used for men with hormonal concerns, though evidence is limited.

Does DIM interact with birth control?⌄

DIM may affect estrogen metabolism and CYP enzymes that metabolize hormonal contraceptives. Consult your clinician about potential interactions.

References

  • Wikidata: 3,3'-Diindolylmethane — Wikidata link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.