Soy formula may inhibit intestinal development in babies
babies, say US researchers, who have carried out tests on newborn
piglets.
Their findings could have a significant impact on makers of soy formula, consumed by around 25 per cent of formula-fed babies in the US.
Researchers found that in newborn piglets fed a formula supplemented with genistein at the level found in soy formula, the number of proliferating cells in the intestine was 50 per cent lower than in piglets fed cow's milk formula alone.
The team from the University of Illinois point out that newborn piglets are a good model for human infants as they have a similar metabolism and physiology.
Concentrations of genistein in the piglets' blood were similar to those of babies fed soy formula, so these data may be applicable to human infants, said Professor Sharon Donovan, who carried out the research released on Pediatric Research online on 7 December.
She explained that 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.
"I'm struck by the fact that these babies are receiving isoflavones at such high concentrations," Donovan said. "Formula is the sole source of nutrition for these infants for the first four to six months of life, when so many important organ systems are developing."
Donovan first reported in the June issue of the Journal of Nutrition that intestinal cells treated with genistein in the amount present in soy infant formula "basically stopped proliferating."
These findings were backed up by the second study on piglets. However although these data are the first to show that genistein is bioactive in the neonatal intestine, Donovan said these results do not mean soy formulas should not be fed to babies.
"Clinical data suggest that soy formulas are safe but even though they appear to be safe, they may not be without effect," she said.
The researcher plans to study the reaction between genistein and other soy isoflavones that likely affect genistein's actions in the intestine.
The study will be published in the February 2005 issue of the journal.
