Soy Baby Formula Safety

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Soy Study

Soy Study

The International Formula Council* Discusses A Study on Soy Infant Formula and Adult Health Outcomes

In 2001 clinical investigators at the University of Pennsylvania and the University of Iowa completed the largest retrospective study to date that examined use of soy formula in infancy and subsequent adult health.  The study was published in the August 15 issue of the Journal of the American Medical Association.  The results indicate those adults fed soy formula as infants were no different from those fed cow-milk formula when any of a large number of health and reproductive outcomes were evaluated.

Soy baby formula, like many other foods, contains phytoestrogens, which are naturally-occurring compounds with some structural similarity to estrogen – but thousands of times weaker in estrogen effects.  The clinical literature offers no evidence of hormonal effects when human infants consume soy protein-based baby formulas.  Additionally, beneficial health effects of phytoestrogens in adults have been recognized.  However, some individuals continue to speculate, based on animal data, that the phytoestrogens in soy baby formula could have adverse effects on human sexual development, fertility, and risk for endocrine-sensitive cancers.  None of these effects were observed in the current study, in which 811adults were interviewed, 248 of whom had been fed soy formula as infants.

"This large study reaffirms the safety of soy baby formula," said Brian Strom, MD, MPH, lead author and Director of the Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine.  "We saw no significant differences between the formula groups, in either females or males, with over 30 outcomes, including height, usual weight, body mass index, indices of pubertal maturation, and a large number of reproductive and other outcomes, including cancer and fertility."

Soy-based infant formulas are an important feeding alternative and have been fed to millions of infants.  Scientific data have demonstrated repeatedly that infants fed soy-based baby formulas develop and grow normally.  The American Academy of Pediatrics Committee on Nutrition recommends that, "in term infants whose nutritional needs are not being met from maternal breast milk or cow milk-based formulas, isolated soy protein-based formulas are safe and effective alternatives to provide appropriate nutrition for normal growth and development."

In the study, young adults, who as infants participated in infant feeding studies conducted at the University of Iowa from 1965-1978, were interviewed about their current health, medical, and reproductive history.  In comparing those fed soy formula vs. those fed cow-milk formula as infants, the results indicated no statistically significant differences in more than 30 growth and development, reproductive, and other health outcomes.  Only two outcomes were statistically significant; female subjects fed soy formula reported slightly longer (about 8 hours) duration of menstrual bleeding (with no difference in menstrual flow) and somewhat more discomfort with menstruation.

When many different factors or variables are examined, it is anticipated that some effects will attain statistical significance even though these effects may be no more than random occurrences with no
clinical relevance. The researchers concluded, "Given the large number of comparisons evaluated in these analyses, the few marginally significant findings may be due to chance."

Breast milk is the ideal and recommended source of nutrition for infant feeding.  However, if parents choose or need to formula-feed their infant, physicians and other health care professionals are best qualified to help parents decide when a soy formula may be appropriate for their infant.

Susan Baker, MD, previous chair of the American Academy of Pediatrics Committee on Nutrition, states, "Parents can feel confident that soy-based infant formulas are safe.  For over 50 years, millions of babies have grown and developed normally on soy-based formulas.  Mother's milk is the best nutrition for babies.  The American Academy of Pediatrics policy is that soy formulas are safe and effective for babies who are not being breast-fed and cannot tolerate a cow-milk formula."

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*IFC is an international association of manufacturers and marketers of formulated nutrition products (e.g., infant formulas and adult nutritionals) whose members are predominantly based in North America. IFC members include all major U.S. manufacturers: Mead Johnson Nutrition; Nestlé Infant Nutrition; Abbott Nutrition Division, Abbott Laboratories; Solus Products; and Wyeth Nutrition.