There are numerous problems caused by soy formulas fed to infants, including difficulty digesting it, lack of sufficient nutrients and toxins. However, one of the biggest problems is the hormonal disruption caused by the isoflavones in soy. Soy isoflavones are phytoestrogens, which are plant-based estrogens that act like hormones. There are enough of them in soy to cause severe disruption to the hormonal systems of infants during a critical period in their hormonal development. The effects are often not seen until later, when they enter puberty (sometimes the phytoestrogens even cause early puberty).