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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASESeptember 15-18, 1996
Brussells, Belgium
SCIENTIFIC PROGRAM
Satellite Symposium
Current Understanding of Soy and Infant Health
Isoflavones in Human Breast Milk and Other Biological Fluids After Soy Consumption
Adrian A. Franke and Laurie J. Custer
Cancer Research Center of Hawaii, 1236 Lauhala St.; Honolulu, HI 96813Increasing evidence suggests that isoflavonoids might protect against various cancers, particularly against breast and prostate cancer due to low cancer rates in Asian populations with high exposure to these agents through consumption of soy foods. Epidemiologic trials concerned with the assessment of the possible cancer preventive role of soy consumption and/or isoflavones require a fast, reliable and affordable technique to measure isoflavone levels in biological fluids favorably through non-invasive protocols.
Therefore, we developed a simple and fast procedure to analyze isoflavonoids and their conjugates from human milk, urine and plasma suitable for metabolic and epidemiologic trials assessing the role of soy foods and/or isoflavones to protect against chronic diseases. A fast and selective HPLC method is presented for baseline separations of the major isoflavonoids found in humans after soy consumption. Analytes were identified by UV scans, by fluorometric and electrochemical detection by GC/SIM-MS and by using internal and external authentic standards.
Applications of the proposed technique showed that isoflavone levels in human milk, plasma and urine increased with increasing soya doses resulting in peak isoflavone levels of 0.2 M, 2.0 M and 20-60 M respectively, after challenge with 20 g roasted soybeans (approximately 40 mg isoflavones). Cancer incidence and severity was shown to be significantly reduced when newborn animals were treated with only three single doses of genistein. Therefore, breastfeeding may be particularly beneficial for infants after mothers consume soy foods by protecting the offspring against cancer through exposure of isoflavones to the newborn at a very early and most critical developmental period. These findings may provide the basis for an alternative explanation of the lower cancer rates observed in Asian populations with high soya consumption due to isoflavone exposure shortly after birth in a critical period of life through mother's milk containing these agents.
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