By Robin SmithSpecial Correspondent
Recent research has raised concern about chemicals in plastic that mimic hormones and might pose risks for infants, but a similar threat is now emerging in a common food – soy.
Animal studies indicate that natural substances in soy have the same hormone-mimicking qualities as some plastic additives, and a debate is unfolding among scientists about how seriously to take the threat.
In a scientific report issued last month, researchers at the National Toxicology Program, based in Research Triangle Park, determined that the risk of soy formula is of “minimal concern” for infant health.
This raised the level of concern from a 1 to a 2 on a five-level scale. The group based its action on recent animal studies and said additional human studies showing health risks are needed before it would consider raising the alert further.
Soy formula has been used for decades as an alternative to milk formula for children who are lactose intolerant or whose families wish to maintain a vegan diet.
In recent years, however, studies in laboratory animals have found a link between estrogen-like substances in soy – natural compounds called isoflavones – and developmental harm in offspring.
Animal studies suggest that fetal or newborn exposure to genistein, a major isoflavone in soy formula, may cause early puberty and other problems later in life.
“Brief exposure to genistein can produce long-lasting effects in rats,” said biologist Heather Patisaul of N.C. State University.
The National Toxicology Program, along with the RTP-based National Institute of Environmental Health Sciences, convened a panel of 14 scientists to evaluate the safety of soy infant formula. The panel reviewed more than 700 studies related to soy formula.
“Animal studies indicate possible harm at blood concentrations comparable to what we see in babies,” said pediatrician and panel chair Gail McCarver of the Children’s Hospital of Wisconsin. But the panel decided a higher level of concern is unwarranted at this time due to insufficient data from human studies.
“Most animal studies have been done on single isoflavones examined one at a time,” said panel member Emilie Rissman, a biologist at the University of Virginia. “But soy formula is composed of more than one type of isoflavone and other components that may interact with each other.”
Not all scientists agree with the panel’s conclusions.
“Why worry about bisphenol A and not soy?” said Patisaul, referring to a hormone-mimicking compound in plastic that has spurred international action. “We see far more significant effects with soy than we do with bisphenol A.”