Common Names

  • I3C
  • Indole-3-methanol
  • 3-(Hydroxymethyl)indole
  • 3-Indolylcarbinol
  • Indolylmethanol

For Patients & Caregivers

How It Works

Indole 3-carbinol has cancer preventive effects, but it has not been shown to treat cancer in humans.

Indole-3-carbinol, also called I3C, is a compound found in vegetables such as broccoli, brussel sprouts, cabbage, cauliflower, and kale. It is known to stimulate detoxifying enzymes in the gut and liver, but has come under more study lately for its potential anticancer properties. Animals fed a diet rich in I3C have slower growth of their cancers.

Laboratory studies show that I3C blocks estrogen activity by interfering with the estrogen receptor. This suggests that I3C might be useful in preventing or treating estrogen-sensitive cancers such as breast and cervical cancers, possibly in addition to tamoxifen. However, not enough studies have been done in humans to determine this. I3C has also been shown to cause cell death in prostate cancer cells in the laboratory.

A few experiments in animals showed that I3C increased the cancer-causing potential of certain environmental carcinogens, but this has not been confirmed in humans.

Purported Uses

  • To prevent cancer
    Laboratory and animal studies suggest that indole-3-carbinol may prevent estrogen-dependent cancers, but only one clinical trial has been performed, which showed that indole-3-carbinol can cause regression of cervical intraepithelial neoplasia (CIN), a condition that can lead to cervical cancer.
  • To detoxify the body
    Indole-3-carbinol stimulates detoxifying enzymes in the gut and liver, but this use has not been tested in clinical trials.
  • To treat viral infections
    No scientific evidence supports this use.

Do Not Take If

  • You are taking cytochrome P450 1A2 substrate drugs: I3C may reduce the effectiveness of these drugs.

Side Effects

  • Skin rash
  • I3C may promote tumor growth in animals exposed to carcinogens. This effect has not been confirmed in humans.
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For Healthcare Professionals

Brand Name

I3C Plus (Health Products Distributors)

Scientific Name

Indole-3-Methanol, 1H-Indole-3-methanol

Clinical Summary

Indole-3-Carbinol (I3C) is a compound found in cruciferous vegetables including broccoli, cabbage and cauliflower. Because diets high in these vegetables retard cancer growth in animals, I3C is thought to be a good candidate for cancer prevention (1).

Several studies demonstrate that 13C can cause cell-cycle arrest (6) (7) and apoptosis (8) (9) (10) (11) (12) in cancer cell lines, has antiangiogenic activity (22), and inhibits tobacco smoke-induced lung adenocarcinoma in mice (23). Studies also indicate that I3C enhances efficacy of gemcitabine (24) and acts synergistically with bortezomib (25) in vitro.

Data from clinical trials show that I3C is effective in the treatment of precancerous cervical dysplasia (2) and vulvar intraepithelial neoplasia (3). In premenopausal women, a supplement containing I3C and 7-hydroxymatairesinol significantly increased the urinary 2:16-hydroxyestrone ratio, a known biomarker for the reduction of breast cancer risk (4). I3C also stimulates detoxification enzymes in the gut and liver (5).

I3C is generally well tolerated when taken orally, but it may promote tumor growth in animals that have been exposed to carcinogens (13). Because it induces cytochrome P450 enzymes (14), I3C may interact with several medications.

Food Sources

Broccoli, brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, mustard greens, rapeseed, rutabaga, turnips

Purported Uses

  • Cancer prevention
  • Detoxification
  • Viral infections

Mechanism of Action

Studies indicate that I3C has potential value as a chemopreventive agent for breast cancer through its estrogen receptor (ER) modulating effect (15). There is also evidence to support the fact that I3C has a different mechanism of action than tamoxifen and that these two can be used synergistically (6). An in vitro study also found that I3C reduces breast cancer cell migration and invasion by inhibiting matrix metalloproteinase (MMP)-2 expression and blocking extracellular signal-regulated kinase (ERK)/Sp1-mediated gene transcription (16). I3C also downregulates expression of the estrogen-responsive genes pS2 and cathepsin-D and upregulates BRAC1 (17). Other in vitro studies show that I3C inhibits expression of cyclin-dependent kinase-6 and induces G1 cell-cycle arrest independent of ER signaling (7).

In human lung carcinoma A549 cells, I3C significantly reduced cell proliferation and induced apoptosis and cell cycle arrest at the G0/G1 phase (12). I3C also lowered the LD50 of gemcitabine and decreased growth of pancreatic cancer cells, possibly through reactivation of the tumor suppressor gene p16INK4a (19). Diindolylmethane (DIM), a metabolite of I3C, can induce apoptosis by modulating the expression of the Bax/Bcl-2 (10). I3C can cause apoptosis of prostate cancer cells in vitro by inhibition of Akt, activation (8). It also holds promise in preventing cancer with a papillomavirus component (20) (21).

One randomized clinical trial suggests that I3C can increase the 2-OH-estrone to -estriol metabolite ratio (18). This is thought to decrease the risk of ER-sensitive breast and cervical cancers.

I3C induces cytochrome P450 1 family, which may lead to potential drug interactions (14).

Adverse Reactions

  • Reported: Some patients experienced skin rash (5) (15).
  • I3C may promote tumor growth in animals exposed to carcinogens. However, this effect has not been confirmed in humans.

Herb-Drug Interactions

  • Cytochrome P450 1A2 substrates: I3C induces CYP 1A2 and can reduce serum concentration of medications metabolized by this enzyme (14).

Herb Lab Interactions

  • In rare cases, small increases in ALT have occurred (5) (15).

Dosage (OneMSK Only)


  1. Bell MC, et al. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol 2000;78:123-9.

  2. Naik R, Nixon S, Lopes A, et al. A randomized phase II trials of indole-3-carbinol in the treatment of vulvar intraepithelial neoplasia. Int J Gynecol Cancer 2006;16(2):786-90.

  3. Indole-3-Carinol(I3C). National Toxicology Program. NIEHS. Accessed November 6, 2012.

  4. Nachshon-Kedmi M, et al. Indole-3-carbinol and 3,3’-diindolylmethane induce apoptosis in human prostate cancer cells. Food Chem Toxicol 2003 Jun;41(6):745-52.

  5. Choi HS, Cho MC, Lee HG, et al. Indole-3-carbinol induces apoptosis through p53 and activation of caspase-8 pathway in lung cancer A549 cells. Food Chem Toxicol. 2010 Mar;48(3):883-90.

  6. Wong GY, et al. Dose-ranging study of indole-3-carbinol for breast cancer prevention. J Cell Biochem Suppl 1997;28-29:111-6.

  7. Bradlow HL, et al. Long-term responses of women to indole-3-carbinol or a high fiber diet. Cancer Epidemiol Biomarkers Prev 1994;3:591-5.

  8. Lyn-Cook BD, Mohammed SI, Davis C, et al. Gender differences in gemcitabine (Gemzar) efficacy in cancer cells: effect of indole-3-carbinol. Anticancer Res. 2010 Dec;30(12):4907-13.

  9. Rosen CA, et al. Preliminary results of the use of indole-3-carbinol for recurrent respiratory papillomatosis. Otolaryngol Head Neck Surg 1998;118:810-5.

  10. Wang ML, Shih CK, Chang HP, Chen YH. Antiangiogenic activity of indole-3-carbinol in endothelial cells stimulated with activated macrophages. Food Chem. 2012 Sep 15;134(2):811-20.

  11. Taylor-Harding B, Agadjanian H, Nassanian H, et al. Indole-3-carbinol synergistically sensitises ovarian cancer cells to bortezomib treatment. Br J Cancer. 2012 Jan 17;106(2):333-43.

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