The potential adverse effects of soybean phytoestrogens in infant feeding.

It is well established that soybean products contain the phytoestrogens daidzein 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 daidzein and genistein than amounts which disrupt the menstrual cycle when fed to pre-menopausal 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.