Altered estrogen metabolism and excretion in humans following consumption of indole-3-carbinol

Nutr Cancer. 1991;16(1):59-66. doi: 10.1080/01635589109514141.


Research studies have demonstrated a strong association between estrogen metabolism and the incidence of breast cancer, and we have therefore sought pharmacological means of favorably altering both metabolism and subsequent risk. Indole-3-carbinol (I3C), obtained from cruciferous vegetables (e.g., cabbage, broccoli, etc.), is a known inducer of oxidative P-450 metabolism in animals. We investigated the effects in humans of short-term oral exposure to this compound (6-7 mg/kg/day over 7 days). We used an in vivo radiometric test, which provided a highly specific and reproducible measure of estradiol 2-hydroxylation before and after exposure to I3C. In a group of 12 healthy volunteers, the average extent of reaction increased by approximately 50% during this short exposure (p less than 0.01), affecting men and women equally. We also measured the urinary excretion of two key estrogen metabolites, 2-hydroxyestrone (2OHE1) and estriol (E3). We found that the excretion of 2OHE1 relative to that of E3 was significantly increased by I3C, further confirming the ongoing induction of 2-hydroxylation. These results indicate that I3C predictably alters endogenous estrogen metabolism toward increased catechol estrogen production and may thereby provide a novel "dietary" means for reducing cancer risk.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Antioxidants / pharmacology*
  • Body Mass Index
  • Body Water / chemistry
  • Estradiol / analysis
  • Estradiol / metabolism*
  • Estradiol / urine
  • Estriol / urine
  • Estrogens, Catechol / urine
  • Estrone / urine
  • Female
  • Humans
  • Hydroxyestrones / urine
  • Hydroxylation
  • Indoles / pharmacology*
  • Male
  • Tritium


  • Antioxidants
  • Estrogens, Catechol
  • Hydroxyestrones
  • Indoles
  • Tritium
  • Estrone
  • Estradiol
  • indole-3-carbinol
  • Estriol
  • 2-hydroxyestrone