Indole-3-Carbinol (I3C): what it does and whether you should try it

Fact: you can get a useful dose of indole-3-carbinol just by eating broccoli and Brussels sprouts. As a supplement, I3C gets attention because it can change how the body handles estrogen and other compounds. That sounds technical, but the practical point is this: people use I3C for hormone balance, gut health, and as part of cancer-prevention research. The hard truth? Supplements aren’t magic. Know what it does, how to use it, and when to skip it.

How I3C works and where it comes from

I3C is a natural compound in cruciferous vegetables—broccoli, cabbage, cauliflower, kale, and Brussels sprouts. When you chew and digest these veggies, I3C forms and partly turns into DIM (diindolylmethane) in the stomach. DIM is often the active player people talk about.

The main thing I3C does is shift estrogen metabolism toward what researchers call "2-hydroxy" metabolites, which are usually less active. That’s why some use I3C when trying to manage estrogen-related conditions. There’s also lab and small clinical research suggesting I3C/DIM may slow growth of certain abnormal cells, but human results are varied and more studies are needed.

Safe use, dosing, and shopping tips

Thinking about taking a supplement? Typical I3C supplement doses range from about 100 mg to 400 mg per day. Many people start low and watch how they feel. DIM supplements are an alternative—some find DIM gentler because it’s what I3C becomes in the body.

Side effects are usually mild: stomach upset, gas, headaches, or changes in urine odor. More rarely, I3C can affect liver enzymes or interact with medications that are processed by the liver. Don’t use I3C if you’re pregnant, breastfeeding, or on hormone therapy unless your doctor says it’s okay. If you have hormone-sensitive cancer or take blood thinners or seizure medicines, talk to your clinician first.

When choosing a product, look for third-party testing (USP, NSF, or similar), clear labeling with the exact I3C or DIM amount, and simple ingredient lists. Avoid supplements that promise cures or use huge doses. A reputable brand will state recommended dosing and list safety warnings.

If you want a food-first approach, eat more lightly cooked cruciferous vegetables—steaming keeps more active compounds than boiling. Supplements are useful if you need a concentrated dose or your doctor recommends them for a specific reason.

Bottom line: I3C has real biological effects and promising early research, but it’s not a one-size-fits-all fix. Start with food, talk to your healthcare provider if you’re considering a supplement, and pick a tested product if you go that route.