Pilot Studies of Estrogen-Related Physical Findings in Infants

Abstract

BackgroundSoy formula containing estrogenic isoflavones is widely used in the United States. Infants consuming soy formula exclusively have high isoflavone exposures. We wanted to study whether soy formula prolonged the physiologic estrogenization of newborns, but available quantitative descriptions of the natural history of breast and genital development are inadequate for study design.ObjectiveWe piloted techniques for assessing infants’ responses to the withdrawal from maternal estrogen and gathered data on breast and genital development in infants at different ages.MethodsWe studied 37 boys and 35 girls, from term pregnancies with normal birth weights, who were < 48 hr to 6 months of age, and residents of Philadelphia, Pennsylvania, during 2004–2005. One-third of the children of each sex and age interval were exclusively fed breast milk, soy formula, or cow-milk formula. Our cross-sectional study measured breast adipose tissue, breast buds, and testicular volume; observed breast and genital development; and collected vaginal wall cells and information on vaginal discharge. We assessed reliability of the measures.ResultsBreast tissue was maximal at birth and disappeared in older children, consistent with waning maternal estrogen. Genital development did not change by age. Breast-milk secretion and withdrawal bleeding were unusual. Vaginal wall cells showed maximal estrogen effect at birth and then reverted; girls on soy appeared to show reestrogenization at 6 months.ConclusionsExamination of infants for plausible effects of estrogens is valid and repeatable. Measurement of breast tissue and characterization of vaginal wall cells could be used to evaluate exposures with estrogen-like effects.

Soy, phytoestrogens and their impact on reproductive health

“…A recent cross-sectional study reported a higher prevalence of breast buds during the second year of life in female infants fed soy-based formula, when compared to their breast or cow-based formula fed counterparts (Zung et al, 2008). Similarly, a prospective study showed that human infants at times exhibited an estrogenized vaginal epithelium when fed soy-based formula as opposed to cowbased formula or breast-milk (Bernbaum et al, 2008). These data suggest that soy formula may prolong the physiologic estrogenization of the newborn.…”

Soybean Phytoestrogens – Friends or Foes?

“…Initially developed as an alternative to bovine milk formulas for babies with a milk allergy, use of soy infant formula became more popular among environmentally oriented population with vegetarian life style. A recent prospective study in human infants observed that female infants fed soybased formulas exhibit estrogenized vaginal epithelium at times when their breast fed or cow milk-based formula fed peers did not (Bernbaum et al, 2008). Patisaul and Jefferson (2010) concluded that further determination if soy infant formula have long-term reproductive health effects should be a public health imperative.…”

Phytoestrogens: Naturally Occurring, Hormonally Active Compounds in Our Diet

“…Furthermore, another study showed that girls who consumed soy formula had a higher maturation index of vaginal cells compared to those fed breast or cow milk. 72 Collectively, both human and animal studies, thus far, support the hypothesis that early life exposures to dietary estrogens can induce effects on the reproductive tract; however, future longterm studies are needed to fully understand the impact of early soy isoflavone exposure. …”