Twenty-seven women with biopsy-proven cervical intraepithelial neoplasia (CIN) classes II or III were randomly assigned to receive, in double-blind fashion, indole-3-carbinol (I-3-C; 200 or 400 mg/day) or placebo orally for 12 weeks. None of the 10 patients in the placebo group had a complete regression of CIN. In contrast, 4 of 8 patients receiving 200 mg/day of I-3-C and 4 of 9 receiving 400 mg/day had a complete regression of CIN after 12 weeks of treatment. In all, 47% of the women receiving I-3-C reverted to normal cervical cytology.

Comment: I-3-C is a compound found in cruciferous vegetables (e.g., broccoli, cabbage, cauliflower, and Brussels sprouts). It has been shown to have anti-cancer activity in animals, possibly by inducing hepatic P450 enzymes that are involved in the detoxification of carcinogens. I-3-C also promotes the metabolism of endogenous estrogens to non-carcinogenic metabolites and may, therefore, be capable of preventing the development of estrogen-dependent cancers. The lower dose of I-3-C used in the present study (200 mg/day) can be obtained by eating about 200 g (7 ounces) of raw cabbage or Brussels sprouts per day.

It has been claimed that diindolylmethane (DIM), a compound that is formed in the stomach from the metabolism of I-3-C, is preferable to I-3-C itself as a therapeutic agent. Most of these claims have come from individuals who appear to have a financial interest in the sale of DIM, and the scientific validity of their statements is difficult to evaluate. Until clinical studies demonstrate the effectiveness of DIM, I will continue to prefer I-3-C for the prevention and treatment of CIN and cervical dysplasia.

Bell MC, et al. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol 2000;78:123-129.