Indole-3-carbinol (I3C) is a substance found in cruciferous vegetables such as broccoli, cauliflower, brussels sprouts, collard greens and kale. Indole-3-carbinol is also available as a dietary supplement and is promising agent for the prevention of estrogen-enhanced cancers.
Anticarcinogenic/Antiestrogenic effect of Indole-3-carbinol (and why is it added to sport supplements)
In certain situations where estrogens are contributing to unwanted effects (such as gynecomastia and certain forms of breast cancer) inducing a state of hypoestrogenism may be beneficial.
Indole-3-carbinol predictably alters endogenous estrogen metabolism which leads to enhanced formation of the inactive catechol estrogens and may thereby provide a novel dietary supplement for reducing cancer risk . Studies in animals [2,3] and humans [1,4,5] as well as in vitro  studies are showing increased 2-hydroxlation by indole-3-carbinol supplementation. 2-hydroxylation leads to the formation of 2-hydroxyestrone and 2-methoxyestrone, which not only are devoid of estrogenic activity, but may also have some antiestrogenic activity [6,7,8].
A study by Yuan et al.  concluded that indole-3-carbinol has anti-estrogenic activities which should prevent cancer in cervical cells (the second most common cancer in women). When 500 mg/day of indole-3-carbinol was administered to humans for 1 week by Jon J. Michnovicz and colleagues , a significantly increased (mean ± SEM) estradiol 2-hydroxylation was noted [29.3% ± 2.1% to 45.6% ± 2.1% (P <.001)].
Indole-3-carbinol is also a potent inducer of cytochrome P450 enzymes in many species , including humans . Cytochrome P450 group of enzymes increase 2-hydroxilation activity .
Indole-3-carbinol and its dimer diindolylmethane are often found in testosterone booster in belief that they will decrease excess estrogen which may result if testosterone is increased above normal levels.
Side effects and precautions
According to WebMD.com , Indole-3-carbinol is likely safe and it seems to be safe for most people when used in medicinal amounts under proper medical supervision. Common side effects include skin rashes and small increases in liver enzymes. Hormone balance should be tested before using indole-3-carbinol in the hope of preventing cancer.
- Michnovicz, Jon J., and H. Leon Bradlow. “Altered estrogen metabolism and excretion in humans following consumption of indole‐3‐carbinol.” (1991): 59-66.
Bradlow, H. Leon, et al. “Effects of dietary indole-3-carbinol on estradiol metabolism and spontaneous mammary tumors in mice.” Carcinogenesis 12.9 (1991): 1571-1574.
Newfield, L., et al. “Estrogen metabolism and human papillomavirus-induced tumors of the larynx: chemo-prophylaxis with indole-3-carbinol.” Anticancer research 13.2 (1992): 337-341.
- Michnovicz, Jon J. “Increased estrogen 2-hydroxylation in obese women using oral indole-3-carbinol.” International journal of obesity and related metabolic disorders: journal of the International Association for the Study of Obesity 22.3 (1998): 227.
- Michnovicz, Jon J., and H. Leon Bradlow. “Induction of estradiol metabolism by dietary indole-3-carbinol in humans.” Journal of the National Cancer Institute 82.11 (1990): 947-949.
- Yuan, F., et al. “Anti-estrogenic activities of indole-3-carbinol in cervical cells: implication for prevention of cervical cancer.” Anticancer research 19.3A (1999): 1673-1680.
- Bradlow, H. L., et al. “2-hydroxyestrone: the ‘good’ estrogen.” Journal of Endocrinology 150.3 Suppl (1996): S259-S265.
- Schneider, Jill, et al. “Antiestrogen action of 2-hydroxyestrone on MCF-7 human breast cancer cells.” Journal of Biological Chemistry 259.8 (1984): 4840-4845.
Badawi, Alaa F., Ercole L. Cavalieri, and Eleanor G. Rogan. “Role of human cytochrome P450 1A1, 1A2, 1B1, and 3A4 in the 2-, 4-, and 16 [alpha]-hydroxylation of 17 [beta]-estradiol.” Metabolism 50.9 (2001): 1001-1003.
- WebMD.com “Find a Vitamin or Supplement – Indole-3-carbinol”. Retrieved 11. July 2013