Donovan said it's an important question to ask because almost 25 percent of formula-fed babies in the United States consume soy formula. Although babies on soy formula appear to grow normally, these formulas contain very high concentrations of genistein, from 32 to 45 milligrams, which is higher than the amount found to affect menstrual cycles in women, she said.
"I'm struck by the fact that these babies are receiving isoflavones at such high concentrations," Donovan said.