The Washington Post

Good news about soy-based baby formula

A study published Monday in the journal Pediatrics finds that babies who are fed soy formula experience normal cognitive development during the first year of their lives – and that their development is on par with that of babies fed milk-based formula.

Babies fed breast milk scored slightly higher on some measures of development than formula-fed infants, but babies in each of the three feeding categories were within healthy limits, the study found.

The research aimed to round out our understanding of the potential impact of feeding soy formula to babies. The authors note that the physical development of babies fed soy formula has been shown to match that of babies fed milk-based formula, but soy’s effect on mental development had not, until this study, been examined. In particular, the authors note, concerns have been raised over the potential effects of the phytochemicals in soy on babies’ early mental development.

Researchers assessed the language, mental and psychomotor development of 391 babies, a third of them breast-fed, a third fed soy formula and a third fed milk-based formula, every three months throughout their first year.

All the formula-fed babies remained on their formula throughout the study. While mothers who breast-fed their babies were encouraged to continue to do so for 12 months, some who weren’t able to switched to milk-based formula at 6 months or later. Data were adjusted to control for socioeconomic status, mother’s age and IQ and the babies’ gender, gestational age, birth weight, head circumference, race, age and diet history.

No developmental differences between the soy-formula and milk-formula groups emerged. The breast-fed babies scored a bit higher than the others on the standardized mental-development test at ages 6 months and 9 months and slightly outscored the soy-fed babies in the psychomotor assessment at 6 months. They also did a bit better on the pre-school language assessment than babies fed milk formula at 3 months and 6 months.

The American Academy of Pediatrics recommends feeding breast milk exclusively for the first 6 months of a baby’s life and continuing breast-feeding after other foods are introduced, at least till the baby turns a year old. The AAP notes that many parents switch from milk-based to soy-based formulas because they believe the former causes their baby’s indigestion, fussiness and colic, but it maintains that soy formula isn’t likely to help solve those problems. Nor, the AAP argues, is soy the best bet for babies being raised vegetarian; breast milk is best for them, according to that organization’s guidelines regarding formula, which further note: “The American Academy of Pediatrics believes that there are few circumstances in which soy formula should be chosen instead of cow milk-based formula in term infants.”

Still, the new research suggests that parents opting to feed their babies soy formula probably aren’t doing their children harm. But the authors notes that the babies in this study will continue to be tracked through age 6. Watch this space.


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