Diindolylmethane (DIM)

Indole-3-carbinol metabolite from cruciferous vegetables, supplement. AEMPS does not register as medicine

ATC code: A11JA-DIM (Diindolylmethane (DIM))

Brand names – supplements

Now DIM, Doctor's Best DIM, Source Naturals DIM, Pure Encapsulations DIM

Supplements are not tested in clinical trials and are not registered as medications.

Mechanism of action

Diindolylmethane (DIM) is the main metabolite of indole-3-carbinol formed in acidic stomach environment after cruciferous vegetable intake (broccoli, cauliflower, Brussels sprouts, kale). In the cell DIM modulates oestrogen metabolism via CYP1A1/1A2 induction, shifting the balance between 2-hydroxyestrone (considered «beneficial» metabolite) and 16α-hydroxyestrone (considered «harmful»). DIM is also a weak partial aryl hydrocarbon receptor modulator and androgen receptor blocker in vitro. The «oestrogen balancing» hypothesis is widely exploited in supplement marketing; no quality RCTs with breast cancer, fibroid or endometriosis risk endpoints.

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Acne and PCOS with hyperandrogenism

Not recommended

Diindolylmethane (DIM) is a compound formed from indole-3-carbinol in cruciferous vegetables; it's marketed as a supplement that balances androgen metabolism and so helps with acne and the hyperandrogenism of PCOS. DIM hasn't shown convincing benefit for this use – there's no solid evidence base for acne or PCOS. For acne and hyperandrogenism in PCOS, other approaches have proven results: topical retinoids and azelaic acid, combined oral contraceptives and spironolactone prescribed by a doctor, and weight loss when there's insulin resistance.

Sources

Polycystic ovary syndrome

Not recommended

DIM is sold to women with PCOS as a «natural antiandrogen» on the androgen receptor partial blockade hypothesis. No evidence base: no quality RCTs in PCOS patients with testosterone, LH or hirsutism scale (Ferriman-Gallwey) endpoints. 2023 PCOS guideline does not mention DIM. SEGO 2017 lists hormonal contraceptives or metformin first-line for PCOS; for marked androgenic features – spironolactone, cyproterone. If DIM was recommended for PCOS instead of standard therapy and workup, consider seeking a second opinion from a gynaecologist-endocrinologist.

Sources

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Safety

Contraindications

Pregnancy and lactation
Children under 18
Hormone-sensitive breast or endometrial tumours (theoretical effect on oestrogen metabolism)
Tamoxifen or aromatase inhibitor therapy (theoretical interaction)
Oestrogen-containing contraceptives (theoretical efficacy reduction via CYP1A2 induction)
Warfarin therapy (potential metabolism induction)

Serious adverse effects

Reduced efficacy of oestrogen-containing contraceptives
Drug interactions with CYP1A2-metabolised drugs (theophylline, clozapine, caffeine)
Allergic reactions (rare)

Common adverse effects

Nausea
Urine colour change (dark yellow or brown)
Headache
Menstrual cycle changes

PregnancyFDA N

No RCT data in pregnancy. AEMPS does not register. DIM as a high concentration of an active oestrogen metabolism modulator should be avoided in pregnancy.

Breastfeeding

No data on milk transfer. Lactating women should avoid.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Diindolylmethane (DIM) used for?

Diindolylmethane (DIM) is evaluated for the following indications with varying evidence strength: Acne and PCOS with hyperandrogenism (evidence tier D), Polycystic ovary syndrome (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Diindolylmethane (DIM)?

Common side effects of Diindolylmethane (DIM) (≥ 1 in 100): Nausea, Urine colour change (dark yellow or brown), Headache, Menstrual cycle changes. See the Safety section for uncommon and serious reactions.

Is Diindolylmethane (DIM) safe during pregnancy?

FDA category N. No RCT data in pregnancy. AEMPS does not register. DIM as a high concentration of an active oestrogen metabolism modulator should be avoided in pregnancy.

Is Diindolylmethane (DIM) compatible with breastfeeding?

No data on milk transfer. Lactating women should avoid.

Who should not take Diindolylmethane (DIM)?

Diindolylmethane (DIM) is contraindicated in: Pregnancy and lactation; Children under 18; Hormone-sensitive breast or endometrial tumours (theoretical effect on oestrogen metabolism); Tamoxifen or aromatase inhibitor therapy (theoretical interaction); Oestrogen-containing contraceptives (theoretical efficacy reduction via CYP1A2 induction). Full list in the Safety section.

Mechanism of action

Safety

Contraindications

Pregnancy and lactation
Children under 18
Hormone-sensitive breast or endometrial tumours (theoretical effect on oestrogen metabolism)
Tamoxifen or aromatase inhibitor therapy (theoretical interaction)
Oestrogen-containing contraceptives (theoretical efficacy reduction via CYP1A2 induction)
Warfarin therapy (potential metabolism induction)

Serious adverse effects

Reduced efficacy of oestrogen-containing contraceptives
Drug interactions with CYP1A2-metabolised drugs (theophylline, clozapine, caffeine)
Allergic reactions (rare)

Common adverse effects

Nausea
Urine colour change (dark yellow or brown)
Headache
Menstrual cycle changes

PregnancyFDA N

No RCT data in pregnancy. AEMPS does not register. DIM as a high concentration of an active oestrogen metabolism modulator should be avoided in pregnancy.

Breastfeeding

No data on milk transfer. Lactating women should avoid.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Diindolylmethane (DIM) used for?

What are the side effects of Diindolylmethane (DIM)?

Is Diindolylmethane (DIM) safe during pregnancy?

FDA category N. No RCT data in pregnancy. AEMPS does not register. DIM as a high concentration of an active oestrogen metabolism modulator should be avoided in pregnancy.

Is Diindolylmethane (DIM) compatible with breastfeeding?

No data on milk transfer. Lactating women should avoid.

Who should not take Diindolylmethane (DIM)?