Over the past 40 years, an estimated 20 million American infants have been fed soy formula. According to a 2008 clinical report published in Pediatrics, the official journal of the American Academy of Pediatrics (AAP), soy protein-based formulas may account for nearly 25 percent of the U.S. formula market. The AAP recognizes that isolated soy protein-based formulas provide nutrition for normal growth and development in term infants. USSEC shares soy-related research as part of its public education initiative. In addition, USSEC highlights the work of experts conducting studies on the health effects of consuming soy, including soy infant formula.
Currently, the Arkansas Children’s Nutrition Center is tracking children from birth in order to determine how infant diets affect future development and health. Thomas M. Badger, PhD, lead researcher for the Beginnings Study at the Arkansas Children’s Nutrition Center (established as a partnership between Arkansas Children’s Hospital and the U.S. Department of Agriculture’s (USDA) Agricultural Research Service), has been investigating the long-term health consequences of diet and nutrition early in life. The research study enrolled 600 children—200 in each of three feeding groups, including breast-fed, milk formula-fed and soy formula-fed. Children in the study now range from ages three years old to nine years old; the project is funded to study these children through puberty. Dr. Badger further describes the Beginnings Study as part of a larger initiative of trying to understand the role of dietary phytochemicals in child development, health and disease prevention.
“We had conducted many animal studies on soy protein and isoflavones, and all the results pointed to benefits to growth, development, body composition and disease (cancer prevention). Unlike those of other groups, our results did not point to isoflavones acting as pure estrogens,” Dr. Badger states. Among the many questions addressed by the study was whether isoflavones were estrogenic in children, and if so, under what circumstances.
Because soy formula contains isoflavones that are classified as phytoestrogens, a common misconception is that soy formula can cause estrogenic effects in infants. Dr. Badger explains, “The major point that all detractors of soy formula are pushing is ‘estrogenicity.’ I am not worried about it, because we are convinced by all of our studies so far that soy formula does not produce estrogenicity or any other potentially adverse estrogen effect.” While the Beginnings Study is not complete, he adds that based on several pieces of evidence, the research team does not expect to find any adverse effects due to the isoflavones of soy formula that might appear later, such as during the teenage years.
“Estrogens act in one way, and only one way. They bind and activate proteins known as estrogen receptors that turn on and turn off specific genes, and result in unique profiles of nuclear and cytosolic proteins that are required for the well-characterized set of estrogen effects (or estrogenicity),” Dr. Badger says. Although isoflavones have been reported to bind to estrogen receptors, they do not activate them the way estrogens do, and the gene and protein expression profiles do not lead to estrogenicity.
Dr. Badger bases his conclusions on several factors. First, purified isoflavones behave differently than foods containing isoflavones. “When one looks at the literature about estrogenic effects, most studies have been conducted with purified isoflavones, which human infants and children are never exposed to,” he says. “Another factor relates to the molecular actions of isoflavones versus estrogens. Our data clearly shows that isoflavones act as selective estrogen modulators, not estrogens. The direction of isoflavone action is toward blocking the adverse actions of estrogens, not in promoting estrogenic actions.”
Finally, he says, the gene and protein expression profiles of estrogens and soy protein (or soy isoflavones) are completely different. “This is the ultimate proof that soy phytochemicals fed to infants in soy formula are not capable of producing estrogenic effects, because they do not activate the metabolic signaling pathways needed to be estrogenic.”