Genistein - an isoflavone

For many years, soy foods have been promoted as vegetarian health foods.  Soy products like tofu, textured vegetable protein, and soy milk continue to gain shelf space in grocery stores.  The massive use of soy in the diet is relatively new, and evidence is starting to accumulate that soy foods may actually be unhealthy.

Soy foods are usually highly processed.  Tofu is made by grinding soy beans to make a slurry (soy milk) which is then coagulated with calcium sulfate (gypsum) or magnesium chloride.  The problem with soy is not its processing, but its content of the isoflavone genistein which can mimic natural human estrogens and may have a variety of harmful effects when eaten in sufficient quantities.  In addition, some bacteria in the digestive system can metabolize soy products to produce equol, another phytoestrogen.

Plant-produced chemicals that mimic hormones have been previously suspected of altering sexual development.  Dr. William Campbell Douglass II writes that girls have become sexually mature at younger ages and that their breasts start to develop in the first and second grade while the boys are experiencing delayed sexual development.  He goes on to say that he believes that this is the reason why boys and men are becoming gay and infertile.

A scientific study at North Carolina State University (NCSU) found that exposure to phytoestrogens alters the sex-specific organization of the hypothalamus, which is the region of the brain that regulates puberty and ovulation.[1]  The two hormone-like compounds from soy-based foods can cause irreversible changes in the structure of the brain, resulting in early-onset puberty, symptoms of advanced menopause, and reproductive health problems.   The NCSU study suggests that humans might be more at risk during gestation.

In light of the available evidence, it seems reasonable that women should avoid eating soy products during pregnancy, and that young children should not be given soy products which may alter their hormonal balance.

[1] Bateman HL, Patisaul HB., Disrupted female reproductive physiology following neonatal exposure to phytoestrogens or estrogen specific ligands is associated with decreased GnRH activation and kisspeptin fiber density in the hypothalamus,
Neurotoxicology, 2008 Jul 6, PMID: 18656497 [news release]