Indole-3-Carbinol Favorably Changes Estrogen Metabolism

Byron's Comments:

An important finding for women and men.

Study Title:

Changes in levels of urinary estrogen metabolites after oral indole-3-carbinol treatment in humans.

Study Abstract:

BACKGROUND:
The oxidative metabolism of estrogens in humans is mediated primarily by cytochrome P450, many isoenzymes of which are inducible by dietary and pharmacologic agents. One major pathway, 2-hydroxylation, is induced by dietary indole-3-carbinol (I3C), which is present in cruciferous vegetables (e.g., cabbage and broccoli).

PURPOSE:
Because the pool of available estrogen substrates for all pathways is limited, we hypothesized that increased 2-hydroxylation of estrogens would lead to decreased activity in competing metabolic pathways.

METHODS:
Urine samples were collected from subjects before and after oral ingestion of I3C (6-7 mg/kg per day). In the first study, seven men received I3C for 1 week; in the second study, 10 women received I3C for 2 months. A profile of 13 estrogens was measured in each sample by gas chromatography-mass spectrometry.

RESULTS:
In both men and women, I3C significantly increased the urinary excretion of C-2 estrogens. The urinary concentrations of nearly all other estrogen metabolites, including levels of estradiol, estrone, estriol, and 16alpha-hydroxyestrone, were lower after I3C treatment.

CONCLUSIONS:
These findings support the hypothesis that I3C-induced estrogen 2-hydroxylation results in decreased concentrations of several metabolites known to activate the estrogen receptor. This effect may lower estrogenic stimulation in women.

IMPLICATIONS:
I3C may have chemopreventive activity against breast cancer in humans, although the long-term effects of higher catechol estrogen levels in women require further investigation.

Study Information:

Michnovicz JJ, Adlercreutz H, Bradlow HL. Changes in levels of urinary estrogen metabolites after oral indole-3-carbinol treatment in humans. J Natl Cancer Inst.  1997 May  21;89(10):718-23.
Rockefeller University Hospital and The Institute for Hormone Research, New York, NY 10016, USA.

Full Study:

http://jnci.oxfordjournals.org/content/89/10/718.long

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