Phytoestrogens in Soy Depress Immune Function

soy-iconAn article published in the Proceedings of the National Academy of Science (May 28, 2002;99(11):7616-7621) has raised new concerns about soy. Researchers injected mice with the soy isoflavones genistein and daidzein and then looked at the thymus gland.

They found that the injections produced dose-responsive decreases in thymic weight of up to 80 percent. In other words, the more isoflavones given, the greater decrease in the weight of the thymus gland. The genistein-injected mice showed a large decrease in the number of immune cells and changes in the thymus, where immune cells mature. Genistein decreased thymocyte numbers up to 86 percent and doubled apoptosis (cell death), indicating that the mechanism of the genistein effect on loss of thymocytes is caused in part by increased apoptosis. In addition, genistein produced suppression of humoral immunity. Genistein injected at 8 mg/kg per day produced serum genistein levels comparable to those reported in soy-fed human infants, and this dose caused significant thymic and immune changes in mice.

Said the researchers: “Critically, dietary genistein at concentrations that produced serum genistein levels substantially less than those in soy-fed infants produced marked thymic atrophy. These results raise the possibility that serum genistein concentrations found in soy-fed infants may be capable of producing thymic and immune abnormalities, as suggested by previous reports of immune impairments in soy-fed human infants.”

These results explain the frequent infections, high fevers and autoimmune problems (including diabetes) that often occur in soy-fed children.

Unlike earlier reports on the negative effects of soy, this study was actually reported in a major newspaper. “A Closer Look at Soy and Babies” appeared in the Science section of the New York Times, May 21, 2002. The article quotes Dr. Paul S. Cook, head of the study, as stating that “parents whose babies did not need to drink soy formula for health reasons, like allergies, should consider using milk-based formula instead, if they do not breast feed.” Mead Johnson Nutritionals, maker of soy formula, naturally defended the use of soy formula. But this article represents the first hole in the media dike and yet another warning to parents to avoid soy formula for their babies.

 

This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Summer 2002.

Sally Fallon Morell is the founding president of the Weston A. Price Foundation and founder of A Campaign for Real Milk. She is the author of the best-selling cookbook, Nourishing Traditions (with Mary G. Enig, PhD) and the Nourishing Traditions Book of Baby & Child Care (with Thomas S. Cowan, MD). She is also the author of Nourishing Broth (with Kaayla T. Daniel, PhD, CCN).

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