Last checked September 2026 against 12 sources · Editorial policy
DIM for estrogen dominance: does it work?
DIM (diindolylmethane) is a compound formed from indole-3-carbinol in cruciferous vegetables, sold as a supplement for estrogen dominance. In trials it changed how estrogen is broken down and raised sex hormone-binding globulin, but it hasn't been shown to relieve estrogen dominance symptoms. In women taking tamoxifen, DIM lowered levels of tamoxifen's active metabolites. Proven ways to lower high estrogen are treating the cause: adjusting estrogen medicines, losing excess body fat and limiting alcohol.
DIM comes from cruciferous vegetables and changes how estrogen is broken down. What studies show, the tamoxifen warning, side effects, and better options for heavy periods.
DIM and estrogen: expectation vs reality
What people often expect
“DIM blocks estrogen and will fix my heavy periods and breast tenderness”
What the evidence shows
DIM isn't an estrogen blocker. In a year-long trial, it shifted estrogen metabolism toward 2-hydroxyestrone and raised SHBG by 25 nmol/L, but didn't change breast density, and the trial didn't test symptoms. A smaller trial in premenopausal women found 75 mg a day didn't significantly change the estrogen metabolite ratio after 30 days.
Does DIM lower estrogen? What the trials show
What is DIM?
Diindolylmethane is a bioactive metabolite of indole-3-carbinol, a compound in cruciferous vegetables. It's promoted for breast cancer prevention and for balancing estrogen, but researchers describe limited evidence of clinically relevant activity or long-term safety from regular use. Supplement doses in trials ranged from 75 mg a day to 150 mg twice a day.
Does DIM lower estrogen?
Not in the way supplements imply. In a randomized trial in 130 women taking tamoxifen, DIM 150 mg twice daily for 12 months raised the ratio of 2-hydroxyestrone to 16-alpha-hydroxyestrone, estrogen breakdown products, and increased SHBG, a protein that binds estrogen in the blood. The published results don't report a drop in blood estrogen levels, and breast density didn't change.
DIM for estrogen dominance
There are no trials of DIM for estrogen dominance symptoms such as heavy periods, breast tenderness or bloating. In premenopausal women, 75 mg a day for 30 days didn't significantly change the estrogen metabolite ratio, although the DIM group lost slightly more body fat. The trial authors said further studies are needed on dosage and effects.
Learn more →DIM and tamoxifen: an important warning
In women taking tamoxifen for breast cancer, DIM reduced blood levels of tamoxifen's active metabolites, including endoxifen. The researchers said more research is needed to see whether this weakens tamoxifen's benefit. If you take tamoxifen or any breast cancer treatment, don't take DIM without your oncology team's approval.
DIM side effects
In the tamoxifen trial, adverse events were minimal and didn't differ between DIM and placebo over 12 months, and compliance was above 91%. Long-term safety data for regular use are limited. Like other supplements, DIM products aren't FDA-approved before sale, so dose and purity depend on the maker.
How to decrease estrogen naturally
Cleveland Clinic lists lifestyle changes that may help high estrogen: a low-fat, high-fiber diet with little processed sugar, reducing body fat, limiting alcohol, managing stress and reducing exposure to synthetic xenoestrogens. Body fat makes estrogen, and heavy drinking reduces how well the body breaks it down, so weight and alcohol are the most direct levers.
Medical ways to lower estrogen
If estrogen medicines are the cause, a doctor can lower the HRT or pill dose. For estrogen-sensitive cancers, aromatase inhibitors stop fat cells making estrogen and GnRH agonists stop the ovaries releasing it. For heavy periods from unopposed estrogen, a progestogen such as the levonorgestrel IUD thins the lining rather than lowering estrogen.
Learn more →Estrogen-blocking herbs and supplements
No herb has been shown to block estrogen in women in the trials we reviewed. Supplements marketed as estrogen blockers aren't reviewed by the FDA before sale. If you're trying to lower estrogen because of a cancer risk or diagnosis, medicines with proven effects are used instead, prescribed by your doctor.
DIM and estrogen by the numbers
+25 nmol/L
130
75 mg
150 mg
DIM trials measured estrogen metabolites and SHBG, not symptoms, and were small.
Ways to lower estrogen compared
DIM supplements
Good for
Shift estrogen metabolism and raise SHBG in trials; minimal side effects over 12 months.Watch
No proof they relieve symptoms; reduce tamoxifen's active metabolites; not FDA-approved.Losing excess body fat
Learn more →Good for
Body fat makes estrogen; after menopause, higher BMI goes with higher estrogen and breast cancer risk.Watch
Takes time and sustained effort.Limiting alcohol
Good for
Heavy drinking reduces the body's ability to break down estrogen.Watch
Helps only if you drink heavily.Adjusting estrogen medicines
Good for
Fixes high estrogen caused by an HRT or pill dose that's too high.Watch
Needs your prescriber.Levonorgestrel IUD for heavy periods
Learn more →Good for
NICE's suggested first treatment for heavy periods in many women; counters estrogen's effect on the lining.Watch
Needs insertion; can cause pain and bleeding.
Before you take DIM or other estrogen-lowering supplements
- Don't take DIM if you use tamoxifen or other breast cancer treatment unless your oncologist agrees.
- Know what you want to change: DIM hasn't been shown to relieve heavy periods, breast pain or bloating.
- Check the dose on the label; trial doses were 75 mg a day to 150 mg twice a day.
- Rule out causes a doctor can treat, such as HRT dose, fibroids or heavy bleeding.
When to see a doctor instead of taking DIM
Heavy periods, bleeding between periods or after sex
See a doctor; these need checking rather than a supplement.
More →You take tamoxifen
Talk to your oncology team before taking DIM.
Breast tenderness or bloating after starting HRT or the pill
Ask about adjusting the dose; side effects often settle within a few weeks.
A new breast lump
See a doctor promptly.
DIM for estrogen dominance: questions women ask
Does DIM lower estrogen?
It changes how estrogen is broken down and raises SHBG, which binds estrogen in the blood, but the main trial didn't report a fall in blood estrogen levels. It hasn't been shown to relieve high-estrogen symptoms.
Does DIM help estrogen dominance?
There's no trial evidence that it does. Studies measured estrogen metabolites and SHBG, not symptoms like heavy periods or breast tenderness.
Related →Can DIM increase estrogen?
It hasn't been shown to raise estrogen. Its measured effects were on estrogen breakdown products and SHBG.
What are the side effects of DIM?
In a 12-month trial, side effects were minimal and similar to placebo. The main concern is that DIM lowered tamoxifen's active metabolites in women taking it for breast cancer.
How can I lower estrogen naturally?
Reduce excess body fat, limit alcohol, eat a high-fiber diet low in processed sugar and manage stress, per Cleveland Clinic. If an HRT or pill dose is the cause, ask your doctor to adjust it.
What supplements lower estrogen?
None has been proven to lower estrogen levels and relieve symptoms. DIM changes estrogen metabolism in trials, but supplements aren't FDA-approved and the evidence on symptoms is missing.
Is DIM an estrogen blocker?
No. Estrogen blockers used in medicine, such as aromatase inhibitors, stop estrogen being made. DIM shifts how estrogen is metabolized and raises SHBG.
Should I take DIM for low estrogen?
No. DIM is marketed for high estrogen, and it doesn't raise estrogen. For low-estrogen symptoms, HRT is the effective treatment.
Related →Does DIM help estrogen balance?
DIM shifts the balance of estrogen breakdown products toward 2-hydroxyestrone and raises SHBG, which is what supplements mean by estrogen balance. Whether that improves symptoms or health outcomes hasn't been shown, and in women on tamoxifen it lowered the drug's active metabolites.
Do cruciferous vegetables lower estrogen?
DIM is formed from a compound in cruciferous vegetables, but the trials we reviewed tested concentrated supplements, not vegetables, and measured estrogen breakdown products rather than estrogen levels. Vegetables are part of a healthy diet; they aren't a proven way to lower estrogen.
Can DIM help with weight loss?
In one small trial in premenopausal women, those taking 75 mg of DIM a day for 30 days lost slightly more body fat than those on placebo. The authors said further studies are needed; it isn't an established weight-loss treatment.
Sources
- Thomson CA, Chow HHS, Wertheim BC, et al. A randomized, placebo-controlled trial of diindolylmethane for breast cancer biomarker modulation in patients taking tamoxifen. Breast Cancer Res Treat. 2017;165(1):97-107.
- Godínez-Martínez E, Santillán R, Sámano R, et al. Effectiveness of 3,3'-Diindolylmethane Supplements on Favoring the Benign Estrogen Metabolism Pathway and Decreasing Body Fat in Premenopausal Women. Nutr Cancer. 2023;75(2):510-519.
- Cleveland Clinic. High estrogen: causes, symptoms, dominance and treatment.
- US Food and Drug Administration. Dietary supplements.
- Cleveland Clinic. Estrone: function, hormone levels and testing.
- NICE. Heavy menstrual bleeding: assessment and management (NG88).
- NHS. Heavy periods.
- NHS. Side effects of hormone replacement therapy (HRT).
- NHS. Breast pain.
- Key TJ, Appleby PN, Reeves GK, et al. Body mass index, serum sex hormones, and breast cancer risk in postmenopausal women. J Natl Cancer Inst. 2003;95(16):1218-26.
- NHS. Types of hormone replacement therapy (HRT).
- Cleveland Clinic. Low estrogen: causes, symptoms, diagnosis and treatment.
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