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Cervical Cancer and Indole-3-Carbinol

Read more about Indole-3-Carbinol.


For the treatment of cervical or any other form of cancer, it is important to keep a well-rounded diet, perhaps take herbal supplements, and certainly determine if any of the medications you are taking are creating deficiencies of key nutrients in your body.

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

Effect of Indole-3-Carbinol on Cervical Cancer

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

  • Facilitating the conversion of estrogen to a less cancer-promoting form ^1,2,5,6 ^
  • Partially blocking the effects of estrogen on cells 4,6,30
  • Directly killing or inhibiting cancer cells 6
  • Reducing levels of free radicals, which can promote cancer by damaging DNA 5

Research Evidence on Indole-3-Carbinol

One small double-blind, placebo-controlled trial found evidence that I3C at a dose of 200 or 400 mg per day can improve the chances of cervical dysplasia returning to normal by itself.3 The related substance, diindolylmethane, might also offer benefit.12

How to Use Indole-3-Carbinol

A 4-week, double-blind, placebo-controlled trial of 57 women found that a minimum dose of 300 mg of I3C daily may be necessary to reduce risk of estrogen-promoted cancers.8 Another study found benefits with 400 mg of I3C per day.7 However, until the overall effects of I3C are better understood, we recommend obtaining this substance through consumption of broccoli family vegetables rather than taking it as a supplement. (See Safety Issues .)

Side Effects and Warnings

#Safety Issues

Studies in rats, chickens, guinea pigs, mice, and dogs suggest that I3C is safe at recommended doses. ^[1] Human trials have found no significant side effects with I3C. ^[2] However, one study in rats found increased abnormalities in male offspring, specifically related to their fertility. ^[3] 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. ^[4] 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. (But you don’t need physician supervision to increase your broccoli intake!)

In addition, because it facilitates the inactivation of estrogen, it is possible that I3C might tend to promote osteoporosis in postmenopausal women and could interfere with estrogen therapies (such as birth control pills and hormone replacement therapy). However, this concern is purely theoretical at this time.

#Interactions You Should Know About

If you are taking:

  • Any medication that contains estrogen (including birth control pills ): I3C might interfere with its action.


  1. Michnovicz JJ. Increased estrogen 2-hydroxylation in obese women using oral indole-3-carbinol. Int J Obes Relat Metab Disord. 1998;22:227-229.
  1. Bradlow HL, Michnovicz JJ, Halper M, et al. Long-term responses of women to indole-3-carbinol or a high fiber diet. Cancer Epidemiol Biomarkers Prev. 1994;3:591-595.
  1. Bell MC, Crowley-Nowick P, Bradlow HL, et al. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol 2000;78:123-129.
  1. Yuan F, Chen DZ, Liu K, et al. Anti-estrogenic activities of indole-3-carbinol in cervical cells: implication for prevention of cervical cancer. Anticancer Res. 1999;19:1673-1680.
  1. Wong GY, Bradlow L, Sepkovic D, et al. Dose-ranging study of indole-3-carbinol for breast cancer prevention. J Cell Biochem Suppl. 1997;28-29:111-116.
  1. Bradlow HL, Sepkovic DW, Telang NT, et al. Multifunctional aspects of the action of indole-3-carbinol as an antitumor agent. Ann N Y Acad Sci. 1999;889:204-213.
  1. Bell MC, Crowley-Nowick P, Bradlow HL, Sepkovic DW, Schmidt-Grimminger D, Howell P, Mayeaux EJ, Tucker A, Turbat-Herrera EA, Mathis JM. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol. 78(2):123-9.
  1. Wong GY, Bradlow L, Sepkovic D, Mehl S, Mailman J, Osborne MP. Dose-ranging study of indole-3-carbinol for breast cancer prevention. J Cell Biochem Suppl. 28-29():111-6.
  1. Chen DZ, Qi M, Auborn KJ, Carter TH. Indole-3-carbinol and diindolylmethane induce apoptosis of human cervical cancer cells and in murine HPV16-transgenic preneoplastic cervical epithelium. J Nutr. 2001;131:3294-302.
  1. Meng Q, Yuan F, Goldberg ID, et al. Indole-3-carbinol is a negative regulator of estrogen receptor-alpha signaling in human tumor cells. J Nutr. 2000;130:2927-293l .