PHYTOESTROGENS IN SOY-BASED INFANT FOODS - CONCENTRATIONS, DAILY INTAKE, AND POSSIBLE BIOLOGICAL EFFECTS

Exposure to estrogenic compounds may pose a developmental hazard to in fants. Soy products, which contain the phytoestrogens, genistein and d aidzein, are becoming increasingly popular as infant foods. To begin t o evaluate the potential of the phytoestrogens in these products to af fect infants, we measured total genistein and daidzein contents of com mercially available soy-based infant formulas, infant cereals, dinners , and rusks. We also assayed phytoestrogens in dairy-based formulas an d in breast milk from omnivorous or vegetarian mothers. In most cases, the glucoside forms of the phytoestrogens were hydrolyzed before sepa ration by HPLC. Mean (+/-SEM) total genistein and daidzein contents in four soy infant formulas were 87 +/- 3 and 49 +/- 2 mu g/g, respectiv ely. The phytoestrogen content of cereals varied with brand, with geni stein ranging from 3-287 mu g/g and daidzein from 2-276 mu g/g. By con trast, no phytoestrogens were detected in dairy-based infant formulas or in human breast milk, irrespective of the mother's diet (detection limit = 0.05 mu g/ml). When fed according to the manufacturer's instru ction, soy formulas provide the infant with a daily dose rate of total isoflavones (i.e., genistein + daidzein) of approximately 3 mg/kg bod y weight, which is maintained at a fairly constant level between 0-4 m onths of age. Supplementing the diet of 4-month-old infants with a sin gle daily serving of cereal can increase their isoflavone intake by ov er 25%, depending on the brand chosen. This rate of isoflavone intake is much greater than that shown in adult humans to alter reproductive hormones. Since the available evidence suggests that infants can diges t and absorb dietary phytoestrogens in active forms and since neonates are generally more susceptible than adults to perturbations of the se x steroid milieu, we suggest that it would be highly desirable to stud y the effects of soy isoflavones on steroid-dependent developmental pr ocesses in human babies.