NEW YORK - One-year-olds raised on breast milk, regular formula or soy formula seem to fare equally well in brain development, a new study suggests.
Past studies have found that, as far as growth, babies given soy formula develop the same as their peers fed breast milk or traditional formula made from cow's milk. But not much was known about signs of brain development, like an infant's early language skills.
The new study, reported in the journal Pediatrics, suggests that brain development is similar, whether babies get breast milk, standard formula or the soy variety.
"I think parents who feed their children formulas, whether soy or milk, should not worry about any adverse effects," senior researcher Thomas M. Badger, a professor at the University of Arkansas for Medical Sciences in Little Rock, said in an email.
In general, experts recommend breast milk as the best source of nutrition for babies.
Groups like the American Academy of Pediatrics (AAP) say that ideally, babies should be fed breast milk alone for six months, then keep getting breast milk along with solid foods for at least their first year.
But that's not always possible for moms to manage. In fact, studies in the US show that while close to two-thirds of infants start on breast milk, most parents switch to formula within their babies' first six months.
And Badger, who also directs the Arkansas Children's Nutrition Center, said that parents "should not feel guilty for using formula."
For their study, Badger and his colleagues followed 131 infants who were breastfed exclusively for at least six months; 131 who were started on milk-based formula within their first two months of life; and 129 who were given soy formula.
The researchers gave the babies standard tests of language skills and other developmental milestones every three months during their first year.
In the end, the study found, the average scores were similar in all three groups - and all were within normal range.
The breastfed babies did show a "slight potential advantage" in scores, the researchers say. But it's not clear whether that numerical edge would make a difference in real life.
Right now, the AAP ranks cow's milk formulas as the second choice to breast milk, with soy formulas coming in third.
That is partly because milk formulas have been around much longer and have not been linked to any adverse effects, Badger explained.
With soy formulas, there has been a theoretical concern that certain plant compounds in soy could be harmful to children's development. But that, Badger said, is mainly based on lab studies where animals were given large doses of those compounds, purified from soybeans.
Badger is on the science advisory board to the Soy Nutrition Institute, an industry-funded group. The study itself was funded by the US Department of Agriculture.
He said his team will continue to follow the children in this study, until at least age 6, to see if there are any long-range effects linked to soy formula.
"In five years, our study will be complete and we will know much more about the longer-term effects," Badger said.