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What is it? Overview Usage Side Effects and Warnings

What is Indole-3-Carbinol?

Indole-3-carbinol (I3C), a chemical found in vegetables of the broccoli family, is thought to possess cancer preventive properties.

Indole-3-carbinol appears to work in several ways:

  • Facilitating the conversion of estrogen to a less cancer-promoting form 1
  • Partially blocking the effects of estrogen on cells 2
  • Directly killing or inhibiting cancer cells 3
  • Reducing levels of free radicals, which can promote cancer by damaging DNA 4

I3C is being studied as a chemopreventive agent: a substance that helps prevent cancer . Numerous animal studies suggest that I3C might help reduce the risk of estrogen-sensitive cancers, as well as other types of cancer. 5 One double-blind, placebo-controlled study in humans suggests that it can help reverse cervical dysplasia , a precancerous condition. 6 Weaker evidence hints at benefits for vulvar intraepithelial neoplasia, a precancerous condition of the vulva. 7 Note: Do not attempt to treat cervical dysplasia, or any other precancerous or cancerous condition, without physician supervision.

Some evidence indicates that I3C might also help prevent recurrences of a rare condition called respiratory papillomatosis. 8 This disease involves benign tumors in the lungs,...

Safety Issues

Studies in rats, chickens, guinea pigs, mice, and dogs suggest that I3C is safe at recommended doses. 9 Human trials have found no significant side effects with I3C. 10 However, one study in rats found increased abnormalities in male offspring, specifically related to their fertility. 11 For this reason, I3C supplements should not be used by pregnant women.

There are other concerns with I3C, as well. For example, despite its overall anticancer effects, there is some evidence that I3C has tumor-promoting properties under certain circumstances. 12 For this reason, long-term use of concentrated I3C supplements may not be safe. In addition, individuals who have already had cancer shouldn’t use I3C (or any other supplement) except under physician supervision....