HealthDay News — Infants given soy-based formula have reproductive system differences compared with those given cow-milk formula or breast milk, according to a study published online March 1 in the Journal of Clinical Endocrinology & Metabolism.
Margaret A. Adgent, PhD, from the Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues compared estrogen-responsive postnatal development in infants exclusively fed soy formula (102 infants), cow-milk formula (111), or breast milk (70) from birth to 28 weeks in boys or 36 weeks in girls.
The researchers found that vaginal cell maturation index trended higher and uterine volume decreased more slowly in soy-fed girls versus cow-milk-fed girls. There were, however, no differences in trajectories of breast-bud diameter and hormone concentrations. Estradiol was not detectable and no significant observed differences were seen between boys fed cow-milk formula versus soy formula. Compared to soy-fed infants, breastfed infants differed in vaginal cell maturation index, uterine volume, and girls’ estradiol and boys’ breast-bud diameter trajectories.
“Relative to cow-milk formula-fed girls, soy formula-fed girls demonstrated tissue and organ-level developmental trajectories consistent with response to exogenous estrogen exposure,” the authors write.