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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
Determination of Dietary Isoflavone Exposure in Infants Fed Breast Milk, Cow Milk or Soya Formula"
GE Joannou, *M. Silink, *P. McVeagh, *GE Kelly,+ M.A. Waring+
* The New Children's Hospital, Hawkesberry Rd., Westmead, NSW 2145, Australia
+ NORVET, LTD., 140 Wieks Rd., North Ryde, NSW 2113 Australia.The plan isoflavones - genestein, daidzein and coumestrol - have been shown in some rodent studies to induce developmental abnormalities of the immature reproductive tract when fed at relatively high dosage to neonatal animals. This effect is ascribed to the ability of these compounds to act as weak oestrogens/androgens or anti-oestrogens/ anti-androgens under differing physiological conditions. This has led to some speculation that soya-based infant formulae which can contain these isoflavones might pose a health risk to the human neonate. The counter arguments proposed are (a) that soya-based infant formulae typically have very low isoflavone content compared to soya flour (0.002 vs. 0.2% respectively); (b) that soya-based infant formulae have been used extensively in infants over 40 years with no reported ill-effects in this respect, (c) that the excretion of dietary isoflavones in breast milk suggests that breast-fed infants in traditional cultures typically are exposed to high dietary isoflavone levels without reported ill-effect, and (d) that dietary isoflavones in fact may be beneficial micro-nutrients for the infant.
This presentation describes a study intended to determine the comparative levels of exposure of infants to dietary isoflavones when fed either cow milk, soya formula, or breast milk from mothers with high or low dietary isoflavone levels. It also will assess the ability of infants to metabolise and assimilate the dietary isoflavones and isoflavonoid metabolites and to determine some physiological responses of the infants to the isoflavones.
There will be five treatment groups: infants who are not breast-fed and who receive a complete diet from time of birth of a cow milk formula (Group 1) or one of two soya-based formulae (Groups 2 and 3); infants breast-fed from time of birth and whose mothers have either a high dietary soya isoflavone intake (>200 mg per week) (Group 4) or a low dietary soya isoflavone intake (< 30 mg per week).
Levels of the isoflavones and isoflavonoid metabolites will be determined by GC-MS in breast milk and urine from mothers in Groups 4 and 5 and in urine from infants in all five treatment groups. Urine and breast milk samples will be collected when the infants are 4, 12, 26 and 52 weeks old. Urinary levels of steroidal hormones also will be determined in the infants at those times.It is hoped that the study will yield information on the following: level of dietary exposure of infants to soya isoflavones when fed soya-based formulae; level of dietary exposure of infants to soya isoflavones and isoflavonoid metabolites when breast-fed; effect of age on the ability of infants to metabolise and assimilate isoflavones and iso-flavonoid metabolites; types and levels of isoflavonoids excreted in human breast milk; the relationship between breast milk and urinary levels and types of isoflavonoids; the effect of urinary isoflavonoid levels in infants on urinary steroidal hormone levels.
This study should provide important data on the level and clinical significance of exposure of human infants to dietary isoflavones in traditional and Western communities.Soy Symposium Home http://soyfoods.com/symposium/
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Indiana Soybean Board