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DIM Supplement for Men: Benefits, Side Effects, Dosage and TRT

Updated: 27 Sept 2026First published: 2 Sept 2023By: Mens Fitness editorial team
DIM Supplement for Men: Benefits, Side Effects, Dosage and TRT

Not medical advice. Product claims come from manufacturers and are attributed to them; research is cited separately. Mens Fitness earns a commission if you buy through our links, at no extra cost to you. How we review.

Short answer: A DIM supplement contains 3,3’-diindolylmethane, a compound your body also makes from cruciferous vegetables. In small human studies it shifts how estrogen is broken down, raising the ratio of 2-hydroxyestrone to 16-alpha-hydroxyestrone in urine. That is not the same as lowering estrogen, and the one placebo-controlled trial in men that measured testosterone did not find a significant change. Human data are limited, most studies were in people with cancer or other conditions, and men on TRT should speak to their prescriber before taking it.

Key facts

Question What the evidence shows
What DIM is A metabolite of indole-3-carbinol, found in broccoli, cabbage and cauliflower (MSK)
Main measured effect Raises the urinary 2-OHE1 to 16α-OHE1 estrogen metabolite ratio (Gee 2016, Thomson 2017)
Testosterone in men No significant change in a 45-man placebo-controlled trial (Gee 2016)
Doses used in studies 50 to 300 mg per dose; up to 300 mg twice daily in a small prostate cancer trial (Reed 2008, Heath 2010)
Reported side effects Nausea, headache, vomiting at 300 mg; low sodium at the highest trial dose; rare case reports of rash and blood clots
Regulation Sold as a dietary supplement; the FDA does not approve supplements before they are marketed (FDA)
Who should ask a doctor first Men on TRT or any hormone drug, anyone on prescription medicines, anyone with a hormone-sensitive condition

What is a DIM supplement?

DIM forms in the gut when you digest indole-3-carbinol (I3C). The Linus Pauling Institute at Oregon State University explains the chain: cruciferous vegetables contain glucobrassicin, chopping or chewing them releases an enzyme that breaks it down into I3C, and in the acidic stomach I3C molecules combine to form DIM and other compounds (LPI). Memorial Sloan Kettering Cancer Center describes DIM as the most studied metabolite of indole-3-carbinol and notes that lab studies suggest anticancer effects, but that “clinical data are limited” (MSK).

A DIM supplement skips the vegetable step and gives a stated number of milligrams of DIM per capsule. In the US it is a dietary supplement. The FDA says it does not have the authority to approve dietary supplements before they are marketed, and it does not test them before they are sold (FDA).

DIM for men: what does it do in males?

In people, the most consistent finding is a change in estrogen metabolism. The liver breaks estrogen down along several routes. DIM appears to favour the 2-hydroxy route over the 16-alpha-hydroxy route, which researchers measure as a higher 2-OHE1 to 16α-OHE1 ratio in urine. This has been seen in:

  • 45 men with prostate cancer given DIM before surgery (significant only in the 200 mg twice daily group compared with placebo) (Gee 2016)
  • A small pilot study of patients with thyroid disease given 300 mg a day for 14 days (Rajoria 2011)
  • 130 women taking tamoxifen, randomised to 150 mg twice daily or placebo for 12 months (Thomson 2017)

Researchers have also described DIM as acting like an anti-androgen in prostate cancer, down-regulating the androgen receptor (Heath 2010). That is worth knowing if you are taking DIM hoping for more androgen activity.

Benefits of DIM for men: what is proven and what is not

  • Shown in small human studies: a shift in urinary estrogen metabolites, as above.
  • Not shown: controlled trials in healthy men showing that DIM improves energy, body fat, strength, mood or libido. We could not find any.
  • Not known: whether the change in estrogen metabolites leads to any health benefit. The Linus Pauling Institute notes that the effects of I3C or DIM supplements on cancer risk in humans are not known (LPI).

For testosterone support in general, our best testosterone booster guide covers other ingredients and lifestyle steps.

Does DIM increase testosterone?

The best direct evidence says no measurable effect. In the Gee trial, 45 men were randomised to DIM at 100 mg or 200 mg twice daily, or placebo, for 21 to 28 days. Testosterone was one of the blood markers measured, and apart from the urine estrogen ratio, changes in blood markers were not statistically significant (Gee 2016). These were men with prostate cancer over a few weeks, so the result does not settle the question for younger, healthy men, but it is the only controlled data in men we found.

There is a 2026 single case report of a 78-year-old man whose testosterone rose while taking 100 mg of DIM daily for three months (Arnold 2026). The authors themselves say one case needs validation in larger studies. A case report cannot show cause and effect.

Does DIM lower estrogen in men?

Not in the simple sense. The studies above measured how estrogen is metabolised, not a drop in blood estradiol. In a large retrospective lab database study, people reporting DIM use had different urine estrogen profiles, including a higher 2-OHE1 to 16-OHE1 ratio, but those data were almost entirely from women, and the authors work for the lab that ran the tests (Newman 2024).

It also helps to know that estrogen is not the enemy in men. In a 16-week NIH-funded trial in 400 healthy men aged 20 to 50, researchers suppressed hormones and then gave testosterone with or without anastrozole, a drug that blocks conversion of testosterone to estradiol. Estrogen deficiency mainly explained increases in body fat, and low testosterone and low estrogen both contributed to a decline in sexual function (Finkelstein 2013). Pushing estrogen down without a medical reason is not automatically a benefit.

DIM side effects in males: is DIM safe for men?

Short-term trials in men describe DIM as well tolerated, but the numbers are small:

  • Single doses in healthy adults: no side effects linked to DIM up to 200 mg. At 300 mg, one of six people reported mild nausea and headache, and one reported vomiting (Reed 2008).
  • Higher repeated doses: in 12 men with prostate cancer, two of the four men on 300 mg twice daily had asymptomatic low blood sodium (hyponatremia) found on routine blood tests (Heath 2010).
  • Case reports: a 65-year-old man developed a leg blood clot and pulmonary embolism after taking DIM for three to four months, though he also had other clot risk factors (Bui 2016). There is a published case of a severe drug rash (DRESS) attributed to DIM (Le 2016). MSK also lists visual disturbance and a stroke case report (MSK).

Case reports do not prove DIM caused these events. Stop and get checked if you notice leg swelling, chest pain, breathlessness, a rash or vision changes.

Drug interactions: DIM affects liver enzymes (CYP450). In the tamoxifen trial, DIM lowered blood levels of tamoxifen’s active metabolites, including endoxifen (Thomson 2017). MSK advises caution with medicines processed by CYP450 or MDR1, because DIM may reduce their effect (MSK). The Linus Pauling Institute adds that DIM may increase CYP1A2 activity, which could lower blood levels of medicines cleared by that enzyme (LPI). If you take any regular medicine, ask a pharmacist before adding DIM.

We found no long-term safety data in healthy men.

DIM and TRT: should men on testosterone therapy take DIM?

If you are on testosterone replacement therapy, talk to the clinician who prescribes it before starting DIM. There are three practical reasons:

  1. Your estradiol is part of your treatment plan. Testosterone is converted to estradiol, and the Finkelstein trial showed estradiol matters for body fat and sexual function in men (Finkelstein 2013). Your prescriber uses your blood results to judge dose and side effects.
  2. DIM has shown anti-androgen activity in prostate cancer research (Heath 2010). No study we found tested DIM in men on TRT, so nobody knows how the two interact.
  3. Monitoring. The American Urological Association guideline stresses on-treatment monitoring for men on testosterone therapy (AUA 2018). A supplement that may change hormone metabolism can make those results harder to read.

There is no “best DIM for TRT”. We will not suggest a dose for men on TRT. The only doses we can report are those used in the studies below, none of which involved TRT.

DIM dosage for men: what did studies use?

There is no established dose. Here is what researchers gave, and to whom:

Study Who Dose How long
Reed 2008 Healthy men and women Single doses of 50 to 300 mg One dose
Gee 2016 45 men with prostate cancer 100 or 200 mg twice daily 21 to 28 days
Heath 2010 12 men with prostate cancer 75 to 300 mg twice daily Months
Rajoria 2011 Patients with thyroid disease 300 mg a day 14 days
Thomson 2017 130 women on tamoxifen 150 mg twice daily 12 months

Three useful details:

  • Most trials used an absorption-enhanced formulation (BioResponse DIM, or BR-DIM), so the milligrams on a retail label may not be comparable.
  • In the healthy volunteer study, only one person at the 50 mg dose had any measurable DIM in the blood, and going from 200 mg to 300 mg did not raise peak blood levels but did bring the first side effects (Reed 2008).
  • In the prostate cancer dose study, 300 mg twice daily was the highest dose tested and the researchers recommended 225 mg twice daily for further study (Heath 2010). That was a cancer trial, not a guide for healthy men.

Follow the product label and ask a doctor or pharmacist if you are unsure.

What is the best time to take DIM?

We found no study comparing morning and evening doses, or DIM with and without food, in men. The trials above mostly split the daily amount into two doses. Follow the label on the product you use. The DIM 3X label, for example, says to take its capsules with meals (NIH DSLD).

DIM for gyno, bodybuilding and libido

Does DIM help gynecomastia (gyno)?

No study we found tested DIM as a treatment. The NHS lists causes including hormone changes, being overweight, certain medicines, anabolic steroids and conditions such as kidney disease or an overactive thyroid, and advises seeing a GP for a breast lump, nipple discharge or skin changes (NHS). Breast growth in a man needs a proper diagnosis, not a supplement.

Bodybuilding and libido

  • Bodybuilding: no controlled trial we found shows DIM increases muscle, strength or fat loss. One case report describes DIM being sold for “augmentation of physical fitness”, but that is marketing, not evidence (Bui 2016).
  • Libido: no trials of DIM on sexual desire in men were found. Sexual function in men depends on both testosterone and estradiol (Finkelstein 2013), so lowering estrogen is not a reliable libido fix.

DIM from food vs DIM supplements

You can get the raw material for DIM from food. Glucobrassicin, the precursor of I3C, is found in broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, kohlrabi, mustard greens, radish, rutabaga and turnip (LPI). The differences from a supplement:

Cruciferous vegetables DIM supplement
Amount of DIM Not fixed. Glucobrassicin is only about 8% to 12% of the vegetables’ glucosinolates, and how much I3C forms depends on processing and preparation (LPI) A stated milligram amount per capsule
Evidence on this page The human trials above did not test diets The human trials above tested DIM capsules, mostly BR-DIM

What about indole-3-carbinol supplements? I3C is sold on its own, and the Linus Pauling Institute notes that I3C is not detected in blood after oral doses, while DIM is, because I3C is converted in the stomach (LPI). Neither form has been shown to improve health outcomes in healthy men.

Prescription drugs that block estrogen production, such as the anastrozole used in the Finkelstein trial, are a separate category and are only for use under medical supervision.

How to choose a DIM supplement

We do not rank DIM brands, because no head-to-head trials exist. These are the objective points to check on any label:

  1. DIM per serving vs doses in studies. Check milligrams of DIM per capsule and capsules per day, and compare the daily total with the study doses above. The FDA notes that no law limits the amount of a dietary ingredient in a serving; the manufacturer decides (FDA). More is not better: side effects appeared at 300 mg.
  2. Form and absorption. Most trials used BR-DIM, an absorption-enhanced form. If a product says “enhanced absorption”, check whether the label names the form or cites a study of that formula. A marketing claim is not a measurement.
  3. Added ingredients. Each extra ingredient is another thing to check for interactions. A short list with every amount stated is easier to assess than a proprietary blend.
  4. Third-party testing. The FDA does not test supplements before sale and suggests consumers can contact the manufacturer or a commercial laboratory about a product’s content (FDA). Look for a named independent lab and a batch certificate of analysis. “Made in a GMP facility” is a manufacturing standard, not a content test.
  5. Price per month. Divide the bottle price by the number of days it lasts at the label dose. A 90-capsule bottle lasts 90 days at one capsule a day and 45 days at two.
  6. Seller, refund terms and warnings. Check who sells it, how long any money-back window lasts, and whether the label tells people with medical conditions or on medicines to check with a doctor.

Comparison box: PrimeGENIX DIM 3X

PrimeGENIX DIM 3X is sold by Leading Edge Health. These facts come from the label record in the NIH Dietary Supplement Label Database and from the official site.

  • DIM per capsule: 200 mg (NIH DSLD label 306918, entered 22 Mar 2024; an earlier 2022 label entry lists the same amounts)
  • Other listed ingredients per capsule: vitamin E 30 IU, AstraGin 2.5 mg, BioPerine (black pepper extract) 2.5 mg, in a vegetarian capsule
  • Label directions: one to two capsules daily with meals, which equals 200 to 400 mg of DIM a day
  • Bottle size: 90 capsules, so 45 to 90 days depending on dose
  • Form: the label says “3x absorption” and “enhanced absorption”. These are maker claims. The label does not say the DIM is BR-DIM, and we found no published study of this formula.
  • Guarantee: 67-day money-back guarantee per dim3x.com (checked 27 Sep 2026)

How it compares with the studies: 200 mg per capsule matches the single dose that was well tolerated in healthy adults, and 400 mg a day matches the 200 mg twice daily arm of the Gee trial (Reed 2008, Gee 2016). Those trials used BR-DIM, so the numbers may not be equivalent. No independent trial of the finished product was found.

Read our full DIM3X review or see the official DIM 3X site (affiliate link). If you are on TRT, any hormone medicine or any regular prescription, speak to your doctor before trying any DIM product.

You can read how we assess products on our how we review page.

FAQ

What is a DIM supplement? DIM (3,3’-diindolylmethane) is a compound the body makes from indole-3-carbinol, found in cruciferous vegetables such as broccoli and cabbage. A DIM supplement provides a stated amount in capsule form. The FDA does not approve dietary supplements before they are marketed.

Does DIM increase testosterone in men? The one placebo-controlled trial in men that measured testosterone found no significant change after three to four weeks (Gee 2016). The men had prostate cancer. A single case report of a rise is not enough to show an effect.

Does DIM lower testosterone? We found no trial showing DIM lowers blood testosterone in men. It has shown anti-androgen activity at the receptor level in prostate cancer research, which is different from lowering hormone levels (Heath 2010).

Does DIM lower estrogen in men? Studies show DIM changes how estrogen is metabolised, raising the urinary ratio of 2-hydroxyestrone to 16-alpha-hydroxyestrone. They do not show a reliable drop in blood estradiol in men.

Can I take DIM while on TRT? Ask your prescriber first. No study has tested DIM in men on TRT, and your prescriber manages your estradiol and testosterone levels through blood monitoring.

How much DIM should a man take? There is no established dose. Studies in men used 75 to 300 mg per dose, often twice daily, mostly in an absorption-enhanced form (BR-DIM) and mostly in men with prostate cancer. Side effects appeared at 300 mg. Follow the product label and ask a doctor or pharmacist if you are unsure.

What are the side effects of DIM in males? In small trials, nausea, headache and vomiting were reported at 300 mg single doses, and low blood sodium was found in two of four men taking 300 mg twice daily. Rare case reports include blood clots and a severe rash, and DIM can interact with some medicines processed by liver enzymes.

When is the best time to take DIM? No study has compared morning and evening doses or taking DIM with and without food. Trials usually split the daily amount into two doses. Follow the label of the product you use.

Is DIM good for gyno? There is no evidence that DIM treats gynecomastia. See a doctor for new breast tissue, a lump or nipple discharge, as the cause needs to be identified.

Can I get DIM from broccoli instead of a supplement? Cruciferous vegetables contain glucobrassicin, which breaks down into indole-3-carbinol and then DIM. The amount formed from food varies with the vegetable and how it is prepared, so food does not give a fixed dose. The human studies on this page tested DIM supplements, not diets.

Sources

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