This information is just too important to keep to myself. I copied it verbatum to reprint here. Still working on the problem at my end--when I'm done-- I will post the entire text of the proposal with references. More later, Marie Davis RN CLC *********** (c) New Zealand Medical Journal 24 May 1995 Pages 208-209. "The potential adverse effects of soybean phytoestrogens in infant feeding." It is well established that soybean products contain the phytoestrogens diadzein and genistein . (1-3) We have measured the levels of these compounds in several soy-based infant formulas available in New Zealand. The quantities recommended by manufacturers for infant feeding provide an intake (per kg body weight) of approximately three to five times as much diadzein and genistein than amounts which disrupt the menstrual cycle when fed to premenopausal women. (4) Exposure to phytoestrogens during soy formula feeding is cause for considerable concern given the greater susceptibility of neonates to oestrogens and the likely duration of exposure through infancy. The soy phytoestrogens act by (1) inhibiting the enzyme 17-b- hyroxysteroid oxidoreductase, type 1, which converts the relatively impotent oestradiol; (2) occupying the oestrogen receptor, thus acting as antagonists to the naturally-produced oestradiol, inhibiting its effects (this behavior is similar to that of another oestrogen agonist-antagonist tamoxifen.) (4) The consequent reduction in oestrogenic action appears to have a useful prophylactic effect against many oestrogen-dependent disorders in adults, including mammary and prostatic tumours. (5) However, the same effect is deleterious in infants. Considerable research has shown that adequate oestradiol is necessary for the imprinting and development of many physical, physiological and behavioral characteristics during the neonatal period and infancy. (6-7) Any decrease in the amount of oestradiol available is potentially harmful. Unfortunately, no specific research has investigated the effects of soy on these characteristics in the human infant, although it has been shown that phytoestrogens are absorbed similarly in infants and adults. (8) It has been claimed that soy-formulas are unlikely to cause harm to infants because they have been used for years without adverse reports (O'Regan, personal communication 1 February 1995). However, another oestrogen, diethylstilbestrol (DES), was administered extensively to women over three decades before the spectrum of harmful effects appeared, some manifesting themselves only when DES offspring reached adulthood. (9) Furthermore, although many women have consumed soy products without reports of problems, when a definitive study was conducted, consumption of 60 g of soy protein per day for 1 month disrupted the menstrual cycle during, and for up to 3 months after administration. (4) Therefore the argument that no adverse effects were observed, therefore none occurred is incogent. It is also plausible that harmful effect have occurred but have not been linked to soy consumption. Other researchers have similar concerns about exposing young infants to phytoestrogens. The introductory program presented by US FDA Department of Health at a recent phytoestrogens conference notes: "phytoestrogens have some of the same capabilities to induce developmental toxicity as do other estrogens" and "given the DES tragedy, it would be foolish to ignore the possibility that some phytoestrogens constitute a developmental hazard." (10) The New Zealand Ministry of health has advised that parents continue to feed their infants soy-based milk formula if they have been advised to do so by their health care specialists' (O'Regan, personal communication 29 March 1995). However, soy-formulas are available at supermarkets enabling parents to choose them without medical advice. It would be prudent for general sales of soy formulas to be stopped. Failing this there is a need for information to be made available to both physicians and parents. As a minimum we suggest a recent review (5) on the risks and benefits of soybean phytoestrogens. Cliff Irvine, Lincoln University; Mike Fitzpatrick, Aukland; Iain Robertson Aukland University Medical School; David Woodhams, Aukland. 1. Mu, PA Phytoestrogen content of processed soybean products,. Food tech 1982;36:60-4. 2. Wang G Kuan SS, Francis OJ, Ware GM, Carman AS. A simplified HPLC method for the determination of phytoestrogens in soybean and its processed products. J Agric Food Chem 1990; 38:185-90. 3. Coward L, Barnes NC, Setchell KDR, Barnes S. Genistein, diadzein and their b- glycoside conjugates: antitumor isoflavones in soybean foods from American and Asian diets. J Agric Food Chem 1993; 41:1961-7. 4. Cassidy A, Bingham S, Setchell KDR. Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenstrual women. Am J Clin Nutr 1994; 60:333-40. 5. Clarkson TB, Anthony MS, Hughes CL. Estrogenic soybean isoflavones and chronic disease. Risks and Benefits Trends Endrocrinol Metab 1995; 6:11-6. 6. Dohler KD. The special case of hormonal imprinting, the neonatal influence on sex In: Csaba G, ed. Development of hormone receptors. Basel:Birkhauser, 1987;103-23. 7. Faiman JSD, Hughes IA, Reves FL Faiman C. Pituitary-gonadal relationship in infancy. 2. Patterns of serum gonadal steroid concentrations in man from birth to two years of age J Clin Endocr Metab 1976; 42:679-86. 8. Cruz MLA, Wong WW, Mimouni F, et al. Effects of infant nutrition on cholesterol synthesis rates. Pediatr Res 1994; 35: 135-40. 9. Apfel RJ, Fisher SM. To do no harm; DES and the dilemmas of modern medicine, New Haven: Yale University Press, 1984. 10. Sheehan DM. The Case For Expanded Phytoestrogen Research. Proc Soc Exp Biol Med 1995; 208:3-5.