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DIM (Diindolylmethane)
DIM (3,3'-diindolylmethane) is the dimerized active metabolite of indole-3-carbinol, the indole produced when you chew cruciferous vegetables.
- Evidence
- Mixed Evidence
- Category
- Women's Health
- Best form
- BioResponse-DIM (BR-DIM, microcrystalline DIM with vitamin E and phosphatidylcholine; the form used in nearly every published clinical trial)
- Effective dose
- 100-300mg/day of BR-DIM (BioResponse-DIM) or an equivalent absorption-enhanced formulation. Trials have used 108-300mg/day
- Lab tested
- 3 of 8 products
- Category
- Women's Health
- Best form
- BioResponse-DIM (BR-DIM, microcrystalline DIM with vitamin E and phosphatidylcholine; the form used in nearly every published clinical trial)
- Effective dose
- 100-300mg/day of BR-DIM (BioResponse-DIM) or an equivalent absorption-enhanced formulation. Trials have used 108-300mg/day
- Lab tested
- 3 of 8 products
Key takeaways
- →DIM reliably shifts the 2-hydroxyestrone / 16-alpha-OH urinary ratio in human trials. That biomarker effect is real.
- →Clinical-endpoint benefits (PMS, breast cancer, cervical dysplasia, acne, BPH) are not established. Mechanism does not equal proven outcome.
- →BR-DIM (BioResponse-DIM, microcrystalline with vitamin E and phosphatidylcholine) is the only form with serious clinical and pharmacokinetic data.
- →Typical clinical dosing is 100-300mg/day of BR-DIM. Avoid in pregnancy and breastfeeding; CYP1A2/2B6 induction may matter for caffeine and some medications.
What Is DIM (Diindolylmethane)?
DIM (3,3'-diindolylmethane) is the dimerized active metabolite of indole-3-carbinol, the indole produced when you chew cruciferous vegetables. The honest one-line verdict is that DIM reliably shifts a urinary estrogen-metabolite ratio in humans, and almost everything else marketed about it is either mechanistic extrapolation or has not been demonstrated in controlled trials. That biomarker shift is real and replicated. Whether it translates to fewer breast cancers, less PMS, clearer skin, or better prostate outcomes is not established.
The replicated finding is the 2-hydroxyestrone : 16-alpha-hydroxyestrone ratio. Michnovicz and Bradlow's 1991 work in Nutrition and Cancer showed that oral indole-3-carbinol increased 2-hydroxylation of estradiol by roughly 50% in healthy adults. Dalessandri 2004 (Nutrition and Cancer) gave 108mg/day of BR-DIM to postmenopausal breast cancer survivors for 30 days and found a significant increase in urinary 2-OHE1 and a 47% rise in the 2-OHE1 / 16-alpha-OHE1 ratio. The mechanistic story (more 2-OH, less 16-alpha-OH) is biologically coherent. The unanswered question is whether that ratio shift, by itself, changes clinical risk.
BR-DIM (BioResponse-DIM) is the form used in nearly every clinical trial. Reed 2008 in Cancer Epidemiology, Biomarkers & Prevention ran a single-dose pharmacokinetic study from 50 to 300mg and showed that absorption plateaus around 200mg, with measurable plasma DIM and good tolerability. Plain crystalline DIM without a carrier matrix is poorly absorbed; the microcrystalline + vitamin E + phosphatidylcholine delivery system is what gets DIM into circulation at the doses trials used. If a product does not specify BR-DIM or an equivalent absorption-enhanced form, you cannot assume the trial pharmacology applies.
The clinical-endpoint trials are smaller and more honest. Bell 2000 (Gynecologic Oncology) gave indole-3-carbinol (the precursor, not DIM directly) at 200 or 400mg/day to 30 women with biopsy-confirmed CIN II-III and saw complete regression in 4/8 and 4/9 of the active arms versus 0/10 placebo. That is interesting but small. Del Priore 2010 (Gynecologic Oncology) ran a larger BR-DIM trial in 64 women with CIN 2/3 and found no therapeutic difference versus placebo. A later Castanon 2012 RCT in low-grade cervical cytology was also negative. So the cervical dysplasia signal exists but did not replicate. For PMS, cyclic mastalgia, breast cancer recurrence, body recomposition, acne, and BPH, there is no clinical-endpoint evidence worth quoting; the case for DIM in those uses is mechanistic and consumer-marketed, not trial-supported. Side effects are usually mild (GI upset, headache, harmless dark or orange urine from DIM metabolites), but DIM induces CYP1A2 and CYP2B6, which matters for caffeine, theophylline, certain antidepressants, and hormonal contraceptives.
Does It Work? The Evidence
How A-F grades workShift in 2-hydroxyestrone : 16-alpha-hydroxyestrone urinary metabolite ratio
Michnovicz & Bradlow 1991 Nutr Cancer (I3C, n=12, ~50% rise in 2-OH); Dalessandri 2004 Nutr Cancer pilot RCT (BR-DIM 108mg in postmenopausal breast cancer survivors, significant 2-OHE1 increase, 47% rise in 2-OH/16a-OH ratio); replicated across multiple smaller studies
Cervical dysplasia (CIN) regression
Bell 2000 Gynecol Oncol (I3C 200-400mg, n=30, regression in active arms vs 0/10 placebo); Del Priore 2010 Gynecol Oncol (BR-DIM 2mg/kg, n=64 with CIN 2/3, no benefit over placebo); Castanon 2012 BJC RCT also negative. Mixed evidence overall.
Breast cancer prevention or recurrence reduction
Only biomarker-shift evidence in breast cancer survivors (Dalessandri 2004; Thomson 2017 trial in tamoxifen users showed metabolite changes only). No clinical-endpoint RCT has shown DIM reduces breast cancer incidence or recurrence.
PMS, cyclic mastalgia, and 'estrogen dominance' symptoms
No quality controlled trials. Marketing claims rely on extrapolation from the metabolite-ratio shift, not from symptom-endpoint trials.
Hormonal acne
No controlled trials in acne populations. Anecdotal reports and a mechanistic argument from androgen and estrogen metabolism, but no clinical evidence.
Body composition or 'estrogen blocker' fat loss claims
No quality human trials in healthy adults pursuing body-composition outcomes. DIM is not an aromatase inhibitor in any meaningful clinical sense.
Benign prostatic hyperplasia (BPH) and prostate health
Heath 2010 phase I in PSA-recurrent prostate cancer showed BR-DIM was safe and modulated androgen metabolites. No quality endpoint trials in BPH symptoms.
| Grade | Claimed Benefit | Key Studies | Our Verdict |
|---|---|---|---|
| B | Shift in 2-hydroxyestrone : 16-alpha-hydroxyestrone urinary metabolite ratio | Michnovicz & Bradlow 1991 Nutr Cancer (I3C, n=12, ~50% rise in 2-OH); Dalessandri 2004 Nutr Cancer pilot RCT (BR-DIM 108mg in postmenopausal breast cancer survivors, significant 2-OHE1 increase, 47% rise in 2-OH/16a-OH ratio); replicated across multiple smaller studies | Supported |
| C | Cervical dysplasia (CIN) regression | Bell 2000 Gynecol Oncol (I3C 200-400mg, n=30, regression in active arms vs 0/10 placebo); Del Priore 2010 Gynecol Oncol (BR-DIM 2mg/kg, n=64 with CIN 2/3, no benefit over placebo); Castanon 2012 BJC RCT also negative. Mixed evidence overall. | Conflicted |
| D | Breast cancer prevention or recurrence reduction | Only biomarker-shift evidence in breast cancer survivors (Dalessandri 2004; Thomson 2017 trial in tamoxifen users showed metabolite changes only). No clinical-endpoint RCT has shown DIM reduces breast cancer incidence or recurrence. | Not There Yet |
| D | PMS, cyclic mastalgia, and 'estrogen dominance' symptoms | No quality controlled trials. Marketing claims rely on extrapolation from the metabolite-ratio shift, not from symptom-endpoint trials. | Not There Yet |
| D | Hormonal acne | No controlled trials in acne populations. Anecdotal reports and a mechanistic argument from androgen and estrogen metabolism, but no clinical evidence. | Not There Yet |
| F | Body composition or 'estrogen blocker' fat loss claims | No quality human trials in healthy adults pursuing body-composition outcomes. DIM is not an aromatase inhibitor in any meaningful clinical sense. | Not There Yet |
| C | Benign prostatic hyperplasia (BPH) and prostate health | Heath 2010 phase I in PSA-recurrent prostate cancer showed BR-DIM was safe and modulated androgen metabolites. No quality endpoint trials in BPH symptoms. | Not There Yet |
How to Choose: Forms, Doses & What Matters
Clinical dose: 100-300mg/day of BR-DIM (BioResponse-DIM) or an equivalent absorption-enhanced formulation. Trials have used 108-300mg/day; pharmacokinetic work caps single doses around 200mg.
Best forms: BioResponse-DIM (BR-DIM, microcrystalline DIM with vitamin E and phosphatidylcholine; the form used in nearly every published clinical trial), Absorption-enhanced DIM with vitamin E + phosphatidylcholine carrier (generic versions of the BR-DIM concept), Generic crystalline DIM (poorly absorbed without a delivery system; not the form studied in trials)
Start at 100mg/day of BR-DIM with food (the fat content in a meal helps absorption). If well-tolerated after one to two weeks, you can titrate to 200mg/day, the dose used in most pharmacokinetic and biomarker trials. Some products dose 100mg twice daily; once-daily 200mg is also reasonable. Doses above 300mg/day are not better-supported and increase the risk of GI upset and headache without clear added benefit. Take with a meal containing fat to support the BR-DIM delivery system. Allow 4 to 12 weeks before judging effects on cycle-related symptoms or skin; metabolite-ratio changes show up faster (weeks) but symptom changes, if they occur at all, take longer. Cycling off periodically (for example, off during the menstrual period or 1 week per month) is a sensible default given the limited long-term safety data.
Who Should Take DIM (Diindolylmethane)?
Adults curious about supporting normal estrogen metabolism with a supplement that has a real mechanistic and biomarker rationale, who also accept that the clinical-endpoint evidence is thin. People most likely to consider DIM are those tracking estrogen metabolites with a clinician, women interested in cruciferous-vegetable phytochemistry concentrated into a supplement, and adults using DIM as a short-term experiment (8-12 weeks) rather than a permanent stack. If you are using DIM to address a specific medical condition like PMS, hormonal acne, fibrocystic breasts, or BPH, recognize you are extrapolating beyond the trial data and consider whether a better-evidenced approach (or a doctor's input) would serve you better first.
Who Should Avoid It?
Not for everyone
Side Effects & Safety
Product Scores
8 products scored on dosing accuracy, third-party testing, cost per effective dose, and label transparency.
The Scorecard: 8 Products Compared
DIMPRO 100 (BR-DIM 100mg), 60 caps
Pure Encapsulations$31.30 ÷ 60 days at 100mg/day (1 serving × 100mg)
The default clinical-grade BR-DIM product. If you want the form that matches the published trial pharmacology with minimal extras, this is it.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
Hormone Advantage (DIM + Pomegranate + Sulforaphane), 60 caps
Thorne$39.00 ÷ 60 days at 250mg/day (1 serving × 250mg)
The trusted-brand pick if you accept the multi-ingredient approach. Thorne's QC program is the main differentiator; the formula adds plausible co-actors but adds noise to evaluating DIM specifically.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
Indolplex with DIM (BR-DIM), 60 tablets
Integrative Therapeutics
$33.00 ÷ 60 days at 60mg/day (1 serving × 60mg)
Indolplex is the original BR-DIM consumer brand; clean and credible, but on a per-mg basis the Pure Encapsulations version is the better value.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
DIM-plus (BR-DIM Complex), 120 vegan caps
Nature's Way
$19.99 ÷ 61 days at 100mg/day (1 serving × 100mg)
If your goal is BR-DIM at the lowest defensible price point, Nature's Way DIM-plus is the value pick; quality is solid even if not premium.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
DIM 200 (with Calcium D-Glucarate), 90 veg caps
NOW Foods$24.99 ÷ 89 days at 200mg/day (1 serving × 200mg)
Solid value pick if you accept that the delivery system is NOW's in-house formulation rather than the BR-DIM trial form.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
DIM 100mg (with BioPerine + Vitamin E), 120 tablets
Source Naturals
$19.99 ÷ 118 days at 100mg/day (1 serving × 100mg)
Reasonable budget option if BR-DIM is out of reach, but recognize you are betting that BioPerine + vitamin E achieves comparable absorption to BR-DIM, which has not been head-to-head tested.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
DIM Capsules 200mg, 120 ct
BulkSupplements
$24.96 ÷ 119 days at 200mg/day (1 serving × 200mg)
Bulk-DIM is fine if you understand that the pharmacology of crystalline DIM without a carrier is not what was tested in trials. As a first DIM product, BR-DIM is a better choice.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
Estroblock PRO Triple Strength (DIM + I3C + chrysin + wasabi), 60 caps
Delgado Protocol
$50.95 ÷ 60 days at 150mg/day (1 serving × 150mg)
Has a strong following among women using DIM for hormonal acne, but on the evidence and per-mg-DIM cost, a clean BR-DIM monoproduct does the same biomarker work for less money.
Prices checked 2026-04-28. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | DIMPRO 100 (BR-DIM 100mg), 60 caps Pure Encapsulations | Hormone Advantage (DIM + Pomegranate + Sulforaphane), 60 caps Thorne | Indolplex with DIM (BR-DIM), 60 tablets Integrative Therapeutics | DIM-plus (BR-DIM Complex), 120 vegan caps Nature's Way | DIM 200 (with Calcium D-Glucarate), 90 veg caps NOW Foods | DIM 100mg (with BioPerine + Vitamin E), 120 tablets Source Naturals | DIM Capsules 200mg, 120 ct BulkSupplements | Estroblock PRO Triple Strength (DIM + I3C + chrysin + wasabi), 60 caps Delgado Protocol |
|---|---|---|---|---|---|---|---|---|
| Brand Score | 89/100Winner | 84/100 | 83/100 | 82/100 | 80/100 | 76/100 | 70/100 | 68/100 |
| Dosing & Form | 22/25Winner | 19/25 | 22/25 | 19/25 | 22/25 | 19/25 | 19/25 | 17/25 |
| Purity | 22/25Winner | 22/25 | 19/25 | 19/25 | 19/25 | 17/25 | 19/25 | 14/25 |
| Value | 22/25 | 20/25 | 19/25 | 24/25Winner | 22/25 | 22/25 | 22/25 | 14/25 |
| Transparency | 23/25Winner | 23/25 | 23/25 | 20/25 | 17/25 | 18/25 | 10/25 | 23/25 |
| Cost/Day | $0.52 | $0.65 | $0.55 | $0.33 | $0.28 | $0.17Winner | $0.21 | $0.85 |
| Dose/Serving | 100mg | 250mg | 60mg | 100mg | 200mg | 100mg | 200mg | 150mg |
| Form | BR-DIM (BioResponse-DIM) capsule, 100mg DIM in microcrystalline + vitamin E + phosphatidylcholine carrier | DIM 250mg + pomegranate extract + sulforaphane glucosinolate (formerly sold as DIM Advantage) | BR-DIM (BioResponse-DIM) tablet, 60mg DIM per tablet (label may list as Indolplex complex) | BR-DIM Complex tablets, 100mg DIM per 2-capsule serving | DIM 200mg + lecithin + calcium D-glucarate veg capsule | DIM 100mg tablet with BioPerine, vitamin E, lecithin | Crystalline DIM 200mg capsule (no specified absorption matrix) | DIM ~150mg + I3C + chrysin + wasabi + phosphatidylcholine + sunflower lecithin |
| Third-Party Tested | ✓ Yes | ✓ Yes | No | No | No | No | ✓ Yes | No |
| Proprietary Blend | No | No | No | No | No | No | No | No |
Frequently Asked Questions
Is DIM safe to take long-term?
Honestly, we don't know. Most clinical trials ran 30 days to 6 months. There is no long-term safety data on daily use beyond 12 months. The conservative approach is to use DIM in short cycles (8-12 weeks), reassess, and not treat it as a permanent supplement. People who use DIM continuously for years are doing so without trial evidence either way.
Does DIM lower estrogen overall, or just shift its metabolism?
It shifts metabolism, it does not directly lower total estrogen. DIM increases the 2-hydroxylation pathway and decreases the 16-alpha-hydroxylation pathway of estrogen breakdown. It is not an aromatase inhibitor and does not reliably reduce circulating estradiol levels in trials. Marketing copy that calls DIM an 'estrogen blocker' is using the term loosely; pharmacologically, that is not what is happening.
What's the difference between BR-DIM and generic DIM?
BR-DIM (BioResponse-DIM) is a microcrystalline DIM combined with vitamin E and phosphatidylcholine designed to actually absorb when you swallow it. Plain crystalline DIM has poor oral bioavailability without a delivery vehicle, so a 200mg crystalline DIM cap may deliver dramatically less to the bloodstream than a 200mg BR-DIM cap. The published clinical and pharmacokinetic trials almost all used BR-DIM. If a label does not specify BR-DIM or describe an absorption-enhanced delivery system, you have less assurance you are getting the dose you paid for.
Can men take DIM?
Yes, DIM has been studied in men too. The most relevant work is Heath 2010, a phase I trial in men with PSA-recurrent prostate cancer that found BR-DIM was safe and shifted androgen and estrogen metabolites. Mechanistically, DIM modulates the same 2-OH versus 16-alpha-OH pathway in men. Whether that translates to clinical benefit for BPH, prostate health, or general 'estrogen detox' goals in men is unproven. Dosing for men is similar (100-300mg/day of BR-DIM).
Will DIM affect my birth control?
Possibly. DIM induces CYP1A2 and CYP2B6, hepatic enzymes that metabolize a range of drugs including some hormonal contraceptive components. The clinical relevance for any given pill or device is not well-characterized in human studies. The honest answer is that the interaction is plausible, the magnitude is unclear, and you should talk to your prescriber if reliable contraception matters to you and you are considering DIM. Do not assume DIM is inert with hormonal birth control.
Does DIM help with hormonal acne?
There are no controlled trials of DIM in acne. Anecdotal reports are common in the supplement community, but anecdote is not evidence. The mechanistic argument (better estrogen metabolism, possible androgen-pathway effects) is plausible but not demonstrated to clear acne in a trial setting. If you try DIM for acne, give it 8-12 weeks, track outcomes honestly, and recognize that better-evidenced acne approaches (topical retinoids, oral contraceptives where appropriate, spironolactone under medical supervision) exist for adults whose acne is genuinely hormone-driven.
Why does my urine turn dark or orange on DIM?
It is harmless. DIM and its metabolites are colored compounds and are excreted in urine. The color change is a marker that the supplement is being absorbed and processed, not a sign of liver or kidney trouble. It tends to be more pronounced at higher doses and with less hydration. If the color change is accompanied by pain, fever, blood in the urine, or other symptoms, that is unrelated to DIM and should be evaluated.
Sources
- Michnovicz JJ, Bradlow HL. Altered estrogen metabolism and excretion in humans following consumption of indole-3-carbinol. Nutr Cancer. 1991;16(1):59-66.
- Dalessandri KM, Firestone GL, Fitch MD, Bradlow HL, Bjeldanes LF. Pilot study: effect of 3,3'-diindolylmethane supplements on urinary hormone metabolites in postmenopausal women with a history of early-stage breast cancer. Nutr Cancer. 2004;50(2):161-7.
- Reed GA, Sunega JM, Sullivan DK, et al. Single-dose pharmacokinetics and tolerability of absorption-enhanced 3,3'-diindolylmethane in healthy subjects. Cancer Epidemiol Biomarkers Prev. 2008;17(10):2619-24.
- Bell MC, Crowley-Nowick P, Bradlow HL, et al. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol. 2000;78(2):123-9.
- Del Priore G, Gudipudi DK, Montemarano N, et al. Oral diindolylmethane (DIM): pilot evaluation of a nonsurgical treatment for cervical dysplasia. Gynecol Oncol. 2010;116(3):464-7.
- Castanon A, Tristram A, Mesher D, et al. Effect of diindolylmethane supplementation on low-grade cervical cytological abnormalities: double-blind, randomised, controlled trial. Br J Cancer. 2012;106(1):45-52.
- Memorial Sloan Kettering Cancer Center. Diindolylmethane: About Herbs reference monograph.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products discussed on this page are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.