dim

DIM (3,3'-diindolylmethane) is a compound the body forms when it breaks down indole-3-carbinol, a substance found in cruciferous vegetables such as broccoli, cabbage, Brussels sprouts, and kale. Sold as a supplement in capsule or tablet form, it is concentrated to provide much more DIM than you would typically get from eating these vegetables.

Rigorous evidence in humans is limited, and no US government health authority (such as the NIH Office of Dietary Supplements, NCCIH, or MedlinePlus) publishes a health fact sheet supporting DIM for any specific condition. Most human research consists of small or early-stage studies, and results have not established that DIM treats or prevents any disease. DIM is sometimes promoted as an antioxidant-type supplement for cancer prevention; on the broader category of antioxidant supplements, NCCIH states that "the current evidence does not support the idea that antioxidant supplements can prevent cancer." That conclusion is about antioxidant supplements in general, not DIM specifically, but it is relevant context for these marketing claims.

There is no established or government-recommended dose for DIM, and products vary widely in how much they contain. Because DIM is not proven to treat any condition and may affect hormones and medications, talk to a clinician or pharmacist before taking it, especially if you have a hormone-sensitive condition or are undergoing cancer treatment.

DIM is sold as a dietary supplement, not regulated as a drug, so product quality and dosing are not guaranteed. Anyone who is pregnant or breastfeeding, has a hormone-sensitive condition, or is receiving cancer treatment should be especially cautious and speak with a healthcare provider first. Because DIM is sometimes marketed as an antioxidant supplement, the general NCCIH cautions about antioxidant supplements are worth noting: NCCIH warns that antioxidant supplements may interfere with chemotherapy and references a study linking use of any antioxidant supplement during chemotherapy to higher risks of breast cancer recurrence and death. These warnings concern antioxidant supplements as a category rather than DIM specifically, but they are a reason to involve your care team before use.

Effects reported in studies and anecdotal use include a harmless change in urine color, headache, and nausea or other digestive upset, with some reports of dizziness at higher doses. High-quality human safety data are limited, so the full side-effect profile of long-term supplement use is not well characterized. These reported effects are not drawn from the cited NCCIH source, which addresses antioxidant supplements generally rather than DIM.

Because DIM is thought to affect how the body processes estrogen and other hormones, it may plausibly interact with hormone therapies, hormonal birth control, or treatments for hormone-sensitive conditions, though this is not established in well-controlled human studies. As a supplement sometimes marketed as an antioxidant, it may also fall under the NCCIH caution that antioxidant supplements can interfere with chemotherapy and other cancer treatments. Review all prescriptions and supplements with a pharmacist or clinician before combining them with DIM.