About 25 percent of formula-fed babies in the U. S. consume soy formula as their sole source of nutrition the first 4 to 6 months. But in two recent studies at the University of Illinois it was shown that the high concentrations of soy isoflavone genistein, found in commercial soy infant formulas, may inhibit intestinal cell growth in babies.

In one study, intestinal cells in culture were treated with genistein and the cells stopped multiplying.

In a second study, one group of newborn piglets were fed a cow's milk-based formula, while another group was fed the same formula plus genistein at a level similar to that in soy formula. In the genistein group, the number of reproducing cells in the intestine was 50 percent lower than piglets fed the cow's milk formula alone.

Donovan says that the results don't mean that soy formula should not be fed to babies since they have not done a study yet in which piglets are fed formula identical to infant soy formula.