I3C supplement: What it does, how to use it, and safety tips

Striking fact: a compound from broccoli can change how your body handles hormones. Indole-3-carbinol (I3C) comes from cruciferous vegetables like broccoli, cauliflower, and cabbage. When you chew these veggies, I3C forms and in your acidic stomach it converts into active compounds such as diindolylmethane (DIM).

People take I3C supplements to support healthy estrogen metabolism, reduce inflammation, and for general detox support. Research shows I3C influences enzymes that break down estrogens, which may help with conditions linked to estrogen imbalance like some forms of PMS, acne, or certain hormone-sensitive conditions. That said, most clinical trials are small and results vary—so think of I3C as a supportive option, not a cure.

How to pick a dose and start safely

Typical supplement doses range from 100 mg to 400 mg per day. If you are new to I3C, start low—try 100 mg once daily for a week, then increase slowly if you tolerate it. Take I3C with food to reduce stomach upset. Keep in mind that DIM supplements are a related option and sometimes better tolerated; some brands combine both.

Who should consider I3C and who should not

If you have hormone-sensitive cancer, are pregnant, breastfeeding, or taking hormone therapy (including birth control, estrogen, or tamoxifen), talk to your doctor before using I3C. The compound affects liver enzymes and can alter how drugs are broken down. Also avoid starting I3C right before key medical tests or surgery without medical advice.

Look for supplements with third-party testing (USP, NSF, or Labdoor) and clear ingredient labels. Steer clear of products that overpromise dramatic results. A cheap, clean product from a reputable brand is smarter than a flashy one with unverified claims.

Watch for side effects: stomach pain, nausea, headache, and changes in menstrual flow are the most common. These usually resolve after stopping or lowering the dose. If you have persistent symptoms or notice mood changes, stop the supplement and check in with a healthcare professional.

Want to get I3C naturally? Eat more cruciferous vegetables: raw or lightly cooked broccoli, Brussels sprouts, cabbage, kale, and bok choy. Supplements can help reach higher doses, but food gives fiber, vitamins, and proven benefits.

Practical tip: track symptoms and any other medications when you start I3C. That helps spot benefits and side effects fast. If you’re trying I3C for a specific issue, give it at least 8–12 weeks before judging whether it helps.

A few studies have tested I3C. For example, a randomized trial in women with cervical dysplasia showed I3C helped some patients when taken for months, and trials looked at markers of estrogen metabolism. These results are promising but limited. If you want to use I3C for a medical condition, work with a clinician to monitor labs and symptoms.

Bottom line: I3C is a well-studied plant compound with real effects on estrogen metabolism. Use it carefully—start low, pick quality brands, and check with your clinician if you take other drugs or have hormone-related conditions.