Abstract
Background: Soy isoflavones may lower breast cancer risk through altered hepatic estrogen metabolism, leading to increased urinary excretion ratios of 2-hydroxyestrone (2OHE1) to 16α-hydroxyestrone (16αOHE1). Materials and Methods: Urinary excretion of 2OHE1/16αOHE1 was measured in 36 healthy, pre-menstrual women before and after ingestion of a soy-protein formula containing 120 mg of isoflavone daily for one month. Since isoflavone absorption and metabolism depends on intestinal bacteria, effects of co-administration of Lactobacillus GG (2×1012) on estrogen ratios and isoflavone excretion were studied. Urinary isoflavone excretion measurements assessed compliance. Results: Soy isoflavone ingestion induced quantitative differences in urinary excretion of estrogen metabolites and isoflavones but failed to alter 2OHE1/16αOHE1 ratios. Co-administration of Lactobacillus GG with soy reduced excretion of total and individual isoflavones by 40% (p=0.08), without altering 2OHE1/16αOHE1 ratios. Conclusion: Isoflavone-rich soy protein administration alone, or with probiotic supplement, did not alter urinary excretion of estrogen metabolites in pre-menopausal women. However, adding concentrated probiotics may alter isoflavone bioavailability.
Footnotes
-
↵* Present address: Strang Cancer Research Laboratory, 1230 York Ave., Smith Building, Box 231, New York, NY 10021, U.S.A.
- Received January 22, 2007.
- Accepted February 2, 2007.
- Copyright © 2007 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved