Soy Formula

I just updated with information from an April 2009 review on soy infant formulas (link). Here is an excerpt from the paper:

“Even though soy isoflavones can bind and activate [estrogen receptors (ER)], they do not behave like typical estrogen agonists but rather as selective ER modulators and, in addition, have many other actions that are ER independent, eg, tyrosine kinase inhibition. It is unfortunate that soy isoflavones have been called “phytoestrogens,” because they are not estrogens and are not truly estrogenic at nutritionally relevant concentrations. The weak isoflavone potency for activating the ERs combined with competition with endogenous estrogens for the ERs make isoflavone-related ER activity minimal when fed in amounts similar to those found in [soy formula], even when fed during early development. Moreover, although some studies have shown similar gene expression profiles for genistein (the major soy isoflavone) and [estrogen] in some tissues in vitro and in vivo, ingestion of soy foods results in a complex mixture containing hundreds of phytochemicals and peptides being introduced to the gastrointestinal tract, many of which are absorbed and have biological actions. This situation is not unlike the mixture of phytochemicals found in a typical meal containing a mixed salad and vegetables.”

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