Does eating soy provide more estrogen than the body can handle?
No, soyfoods do not contain estrogens. Soyfoods contain complex mixtures of proteins, fats, carbohydrates, and bio-active compounds including soy isoflavones. Although isoflavones naturally found in soy are plant “phytoestrogens” that look similar in chemical structure to estrogens, they act differently in the human body and should not be confused with the human hormone estrogen. Isoflavones are bioactive compounds that may improve the health of arteries, prevent certain cancers, and reduce bone loss. (38-42) Numerous human studies have found that men and women consuming 40-70 mg/day of soy isoflavones from soyfoods or soy supplements had no significant changes in testosterone levels or estrogen levels compared to control groups. (43 – 49) Some animal studies that are looking for effects inject or feed a very high dose of a concentrated source of a single isoflavone, such as genistein, which is very different from the way isoflavones are consumed in food. Problems seen in some animals