What Are the Dangers of Soy to Infants?

Introduced in 1909, soy-based formulas are used by 25 percent of U.S. infants, according to the American Academy of Pediatrics. When breastfeeding isn't possible, soy-based formulas are used for infants with an intolerance to formulas based on cow's milk. Preliminary research on soy formulas is inconclusive, but researchers are concerned about potential safety hazards including inefficient nutrient absorption, gastrointestinal reactions, and hormone disruption.

Nutrient Absorption

• Soy contains phytates, a naturally occurring enzyme that interferes with calcium, magnesium, iron, and zinc absorption. Researchers have noted growth problems in some infants fed soy-based formulas.

Aluminum and Manganese Toxicity

• Do not feed soy-based formulas to premature infants.

  Soy-based formulas are high in aluminum and manganese. Aluminum is toxic to the kidneys and nervous system. Renal failure has been noted in premature infants fed these formulas. As such, soy-based formulas are not recommended for premature infants. Some scientists believe the high levels of manganese may be linked to later behavior problems and attention deficit disorders.

Hormone Disruptors

• Soy contains naturally occurring phytoestrogens, which can disrupt natural hormone development. Soy-based formulas have been linked to premature sexual development in girls. Women fed soy-based formulas experience longer and more painful periods.

Gastrointenstinal Reactions

• Enzyme inhibitors make soy-based formulas difficult to digest. Researchers have noted problems from bloody diarrhea to failure to thrive in infants fed soy-based formulas. According to Dr. Lauren Feder, up to 50 percent of infants allergic to cow's milk-based formulas also have soy allergies.

Autoimmune Thyroid Disease

• Soy contains antithyroid agents and is suspected of contributing to hypothyroidism and thyroid cancer in adults. In infants, it is linked to autoimmune thyroid disease.