• Soy milk health dangersSoy beans on green leaf image by Monika 3 Steps Ahead from Fotolia.com
  
  Advocates for soy milk insist that it is nutritional and causes no ill health effects. Supporters claim that soy milk is healthier than cow milk, which may contain growth hormones. However, the most recent research suggests that soy milk may not be as healthy as the soy industry and its advocates claim. There are growing concerns about a link between soy and breast cancer, hypothyroidism, and developmental problems for children fed soy milk.
  
  

Soy and Breast Cancer

• Phytoestrogens are plant hormones that mimic human hormones when ingested. Soy phytoestrogens may contribute to increased risk of breast cancer for women who drink soy milk by affecting the production and metabolism of estrogen in the body. According to Cornell University's Sprecher Institute for Comparative Cancer Research, soy phytoestrogens are associated with lower levels of estrogen in women who consume soy products. Higher estrogen exposure is linked to increased growth of milk ducts in the breasts, which may also be linked to higher risk of breast cancer.
  
  

Thyroid Problems

• Soy has been suspected of interfering with the body's ability to absorb medications that treat hypothyroidism, according to the Mayo Clinic. Soy has also been associated with diet-induced goiter. Goiter is a condition in which the thyroid gland enlarges. This condition can become dangerous if the goiter grows so large that it obstructs breathing or swallowing. Babies who suffer from hypothyroidism need increased medications to replace requisite thyroid hormones if they are fed soy milk. Dr. Naomi Baumslag, clinical professor of pediatrics at Georgetown University Medical School, says that infants who drink soy milk formula are two to three times more likely to develop thyroid disease.
  
  

Effects on Reproduction and Embryos

• An article in Scientific American (November 3, 2009) reported that women who were fed soy milk formula when they were babies had longer periods and more menstrual cramping than those who were not fed soy formula. The report also warned that brain development of embryos might be altered by the phytoestrogens in soy milk, citing a study by Benson Akingbemi, Auburn University developmental biologist.
  
  Soy milk and all soy products contain genistein, which is an isoflavone that interacts with estrogen receptors in the body and causes effects similar to naturally produced estrogen. According to the Scientific American article, one quarter of bottle fed babies in the United States are fed soy milk formula. It is estimated that babies fed soy milk formula exclusively ingest estrogen equivalent to that contained in five birth control pills per day. Male babies who are fed soy milk formula exclusively after birth, and exposed to soy milk phytoestrogens during gestation, had smaller testes when they became adults. It is suggested in the Scientific American article that phytoestrogens in soy milk may result in early sexual development of girls. Premature sexual maturation in girls has been linked to infertility, cessation of normal menstruation, and breast cancer.