A compound formed in the stomach when indole-3-carbinol from cruciferous vegetables condenses under acid conditions. Supplements provide it directly, usually in a microencapsulated form because pure DIM is nearly insoluble.
DIM is sold on an oestrogen-metabolism story: it shifts the balance of oestrogen breakdown toward 2-hydroxylated metabolites, which are traditionally considered the less proliferative route. That shift is real and has been measured in human studies. What has not been shown is that changing this ratio changes anything a person experiences — the outcome trials in breast tissue, prostate lesions and cervical abnormalities are small, short and largely equivocal. DIM is nonetheless widely taken for acne, hormonal symptoms and after testosterone-related supplement use, on reasoning rather than evidence. Its most reliably observed effect is turning urine an alarming shade of orange.
Sold as
Microencapsulated capsule, Softgel with a lipid carrier, Combination with calcium D-glucarate
Standardised to
Milligrams of DIM; absorbable formulations deliver several times more than crystalline DIM — a product without this marker may not resemble what was studied.
Also known as
3,3′-Diindolylmethane, Bioresponse DIM, Absorbable DIM
Regulation: Sold as a dietary supplement in the US with no pre-market efficacy review, and marketed for hormonal conditions where no clinical outcome has been established.
What the research used
The amounts, forms and durations published trials of DIM (diindolylmethane) actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Oestrogen metabolite ratio studies
108 mg
Limited
Absorbable DIM, daily · 4 weeks to 12 months
The dose used in several small trials in women at increased breast cancer risk and in thyroid cancer survivors. The measured outcome was a urinary metabolite ratio, not a clinical event.
Studied for Prostate and cervical studies
150–900 mg
Not enough
Absorbable DIM, daily or divided · 3–12 months
A wide range across small trials. Higher doses produced headache, nausea and darkened urine, and results on clinical endpoints were not convincing.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🍽️With food
Not enough
Taken with food containing fat because DIM is highly lipophilic and crystalline material absorbs poorly. No fed-versus-fasted trial comparison exists.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Not enough
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
There is not enough human research to say DIM affects menopausal or premenstrual symptoms. The oestrogen-metabolism rationale has not been connected to a symptom outcome in a controlled trial.
What may be going on: DIM shifts oestrogen hydroxylation toward the 2-hydroxy pathway and away from 16α-hydroxylation, a change measurable in urine.
Not enough evidence. Not enough human research to say anything useful yet.
No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.
Small trials in men with prostate intraepithelial neoplasia or raised PSA have not produced convincing changes in clinical measures. The studies are underpowered and the results inconsistent.
Not enough evidence. Not enough human research to say anything useful yet.
Randomised controlled trial · European journal of cancer prevention : the official journal of the European Cancer Prevention Organisation (ECP) · 2016 · PMID 26313229
Deep research mode adds each paper’s own conclusion and stated limitations.
DIM is widely used for hormonal acne. No randomised trial has tested it for acne, so this rests entirely on the hormone-metabolism rationale and on anecdote.
Not enough evidence. Not enough human research to say anything useful yet.
No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
A supplement taken specifically to alter oestrogen metabolism is doing something hormonal, and it is being taken without the monitoring that a hormonal medicine would involve. Anyone with a hormone-sensitive cancer, on tamoxifen or an aromatase inhibitor, or on hormonal contraception or hormone replacement, should not add it without their oncologist or prescriber.
Avoid
Not for pregnancy or breastfeeding
A compound taken to change oestrogen metabolism has no safety data in pregnancy, and animal work at high doses raises developmental questions. It should be avoided.
Interaction
Induces and inhibits drug-metabolising enzymes
Interacts withCYP1A2 substrates including some antipsychotics, theophylline and duloxetine
Indole compounds induce CYP1A2 and affect other cytochrome P450 enzymes, which can lower blood levels of medicines cleared by that route. This has been documented for indoles from cruciferous vegetables and is plausible at supplement doses.
Too much
Headache, nausea and darkened urine
Higher doses in trials produced headache, nausea and vomiting. Orange or brown urine is common, harmless and startling if nobody has mentioned it — it is a DIM metabolite, not blood.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.