our leading scientists(2) in New Zealand have raised serious concerns about the high levels of phytoestrogen hormones found in soy-based formulas. Measurements of two phytoestrogens, daidzein and genistein in several brands of soy-based formulas available in New Zealand, found intakes by infants to be extremely high. Intakes were two to three times greater than amounts required to disrupt the menstrual cycle of premenopausal women.
Soy phytoestrogens act as antagonists to the naturally occurring oestradiol, inhibiting its activity. Reduced activity of oestradiol may be beneficial to adults, but for infants it can be deleterious. Research has shown that oestradiol is essential in the "imprinting and development of many physical, physiological and behavioural characteristics during the neonatal period and infancy". Also, any decrease in oestradiol activity has been found to be harmful. As yet no research has been done to document the effects of soy-formula feeding on infant characteristics. Rejecting manufacturers claims that soy formulas have been used for many years without side effects, the authors cite the use of diethylstilbestrol (DES), which was prescribed to women for three decades before harmful effects appeared, to highlight their concerns of long term use and effects. Even the usually conservative US Food and Drug Administration's Department of Health stated at a recent conference on phytoestrogens, "given the DES tragedy, it would be foolish to ignore the possibility that some phytoestrogens constitute a developmental hazard".
The New Zealand Ministry of Health recommends soy-formula feeding only if parents have been advised to do so by health specialists. Yet soy-formulas can be self selected on supermarket and pharmacy shelves. The authors recommend that routine sales of soy-formulas be stopped. At the very least they recommend that physicians and parents be informed.
1. Clarkson, T. B. Anthony, M.S., Hughes, C.L. Estrogenic soybean isoflavins and chronic disease. Risks and benefits. Trends Endocrinol Metab 6:11-16, 1995 Back
2. Irvine, C., Fitzpatrick, M., Robertson, I. and Woodhams, D. The potential adverse effects of soybean phytoestrogens in infant feeding. New Zealand Medical Journal 108:208-209, 1995 Back
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