What it is
DIM forms in the stomach from the indole-3-carbinol released by cruciferous vegetables (broccoli, cabbage, Brussels sprouts). It steers estrogen metabolism toward the 2-hydroxylated pathway, which gave rise to the idea of a hormonal balance to sell. People buy it for hormonal acne, premenstrual syndrome, "estrogen dominance" and, in men, to limit estrogens.
What the label does not say
- The marker moves, the outcome does not: several controlled trials increased the urinary ratio of 2-hydroxyestrone to 16-alpha-hydroxyestrone, but large observational studies found no association between that ratio and the risk of breast or endometrial cancer. Selling the ratio as a balance amounts to selling a laboratory number.
- The largest DIM trial (603 women, 150 mg per day, 6 months) showed no effect on cervical abnormalities or on HPV infection; 31% of the women on DIM had darker urine versus 10% on placebo, with slightly more frequent headaches. Dark urine is not a sign that the product is working.
- No trial found on acne, premenstrual syndrome or estrogens in men. The Health Canada monograph provides for the claims "healthy estrogen metabolism" and "recurrent breast pain", but requires ruling out a serious cause of hormonal imbalance, prohibits use during pregnancy and breastfeeding, and asks you to stop in case of symptoms of low estrogen or liver disorder.
- The Linus Pauling Institute reports that experts advise against broad use of I3C as a supplement until the risks and benefits are better understood.
The forms on the shelf
- DIM: the direct form, 108 to 150 mg per day in the clinical trials according to the Linus Pauling Institute; the Health Canada monograph provides for 60 to 200 mg per day in adults.
- Indole-3-carbinol (I3C): a precursor that has to convert in an acidic stomach; 200 to 800 mg per day in the trials. The Linus Pauling Institute notes that an antacid can prevent that conversion.
Published reference values
- No recommended intake. Trial doses: DIM 108 to 150 mg per day; I3C 200 to 800 mg (300 to 400 mg to change urinary markers). Health Canada: 60 to 200 mg of DIM, adults.
- Reported effects: dark urine, headaches, nausea, dyspepsia, flatulence, mild; slight rise in liver enzymes, rash and digestive symptoms at 600 mg and above of I3C.
- Safety not established during pregnancy and breastfeeding: a Health Canada contraindication.
When
The trials gave it daily for months. For I3C, an antacid taken at the same time can prevent conversion to DIM.
Keep apart from
- Medications metabolized by CYP1A2 (and modestly by CYP3A4): I3C and DIM increase its activity, which can lower the concentrations of these medications; medical monitoring rather than spacing by the hour.
- Proton pump inhibitors and antacids: interfere with the conversion of I3C to DIM.
To mention to a professional
- Hormone-dependent cancer or a history of it, contraception or hormone therapy, medication metabolized by CYP1A2, symptoms of low estrogen, liver disease, pregnancy and breastfeeding: check with a health care professional.
What it is sold for, and what the data show
DIM is sold to balance estrogens, for acne and for premenstrual syndrome. Human trials show a change in urinary markers with no demonstrated clinical benefit, one negative trial of 603 women on the cervix, and nothing on acne or premenstrual syndrome. Broccoli provides the precursor without the bottle.
From the plate first
The precursor, glucobrassicin, comes from cruciferous vegetables: broccoli, cabbage, Brussels sprouts, kale. The amount of DIM formed depends on stomach acidity and is not quantified in the sources consulted.
Sources
- Linus Pauling Institute, Micronutrient Information Center, Indole-3-Carbinol
- Castañon et al., Effect of diindolylmethane supplementation on low-grade cervical cytological abnormalities: double-blind, randomised, controlled trial, British Journal of Cancer, 2012
- Health Canada, natural health product monograph, 3,3'-Diindolylmethane (DIM)
Educational information, drawn from the sources above. It does not replace the advice of a health professional, who remains the reference for your situation, your medications, pregnancy or breastfeeding.