Recent research has raised concern about chemicals in plastic that mimic hormones and might pose risks for infants, but a similar concern 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 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 1 to 2 on a five-level scale. The group based its action on recent animal studies and said additional human studies showing risks are needed before it would raise 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 lab 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.