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Dangers of Soy Infant Formula

author image Janet Renee, MS, RD
Janet Renee is a clinical dietitian with a special interest in weight management, sports dietetics, medical nutrition therapy and diet trends. She earned her Master of Science in nutrition from the University of Chicago and has contributed to health and wellness magazines, including Prevention, Self, Shape and Cooking Light.
Dangers of Soy Infant Formula
Proper nutrition helps infants develop normally. Photo Credit Dynamic Graphics/Creatas/Getty Images

Nutrition plays a crucial role in development, especially during infancy. Breast milk provides an ideal source of nutrition for most infants, but some mothers are unable to breastfeed or choose not to. Formula made with cow's milk is a common alternative, but you may run into problems if your infant is unable to tolerate it. If you are among the millions of parents who choose to feed their infant soy-based formulas as an alternative, be aware of the safety concerns.

Plant Hormones

Soy contains a wide variety of substances known as phytochemicals. A class of isoflavones, commonly referred to as phytoestrogens, may have the weak ability to mimic the human hormone estrogen. Because infants rely solely on formula, this is of particular concern. Average blood levels of genistein -- a primary phytoestrogen in soy -- in infants fed a soy-based formula were 160 times higher than in adults who eat a varied diet, according to the National Toxicology Program 2010 brief.

Some Risks Uncertain

Based on clinical data, the National Toxicology Program, or NTP, concluded that soy formula does not impair growth during infancy in healthy full-term infants. However, evidence is insufficient to conclude whether soy infant formula adversely affects development in areas such as the immune system, thyroid function and reproductive system, according to the NTP's 2010 brief. The NTP identified a need for well-designed human studies to assess the effect of soy formula on those parameters.

Some Fears Put to Rest

Researchers at the Arkansas Children’s Nutrition Center examined developmental differences in babies fed breast milk, formula made from cow's milk and soy formula, using the Bayley Scales of Infant Development and the Preschool Language Scale-3. Researchers assessed the infants every three months for one year. The study found all developmental scores were in the normal range, although breast-fed infants scored slightly better in cognition. This study did not, however, examine critical areas of concern, such as thyroid function, reproductive development and immune system development. The results were published in the June 2012 issue of the journal "Pediatrics."


While many experts agree that breast milk is the most ideal source of nutrition for infants, it isn't always a viable option. Talk to your pediatrician if you need help determining the best source of nutrition for your infant. If you have concerns about soy-based formulas, alternatives do exist. You can feed your baby an amino formulation, according to the NIH. Amino acids serve as the building blocks of protein. These formulations also contain other nutrients that facilitate healthy development. Formula made from lactose-free cow's milk is another alternative.

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