Soy Milk Formulas Won't Hurt, but Don't Always Help

A pediatrician group weighs in on the merits of the two baby formulas.

May 6, 2008 — -- To soy or not to soy?

Parents often have to make the choice when it comes to feeding formula to their babies.

But in a clinical report based on a review of available information just released, experts have delivered the definitive word on feeding infants soy protein-based formulas versus cow milk formulas: Why use soy at all?

The first year of life is a time of rapid growth and development, unmatched by any other time in life. Infants are sustained by a single nutrition source, so it has to be the ideal one.

While cow milk and soy formulas are nutritionally the same, the long-term benefits — and drawbacks — to using soy formulas are still unclear.

"Why feed it when there is no indication for it?" said Dr. Jatinder Bhatia, a professor of pediatrics at the Medical College of Georgia, and one of the lead authors of the report by the Committee on Nutrition for the American Academy of Pediatrics. "Cow milk is the preferred choice if you cannot breast-feed."

Formula for Fussiness

Soy protein-based formulas have been part of general pediatric practice for more than 50 years. Physicians, sometimes attributing fussiness to cow milk formula, recommended a switch to soy, unnecessarily, some pediatricians say. Soy formula became a quick fix go-to for problematic infants.

"When a mother came into the office complaining about colic, fussiness, excessive spitting, constipation — you name it — and attributing it to the infant's cow milk formula, the first thing I did was change the infant to a soy formula," said Dr. Frank Greer, a professor of pediatrics at the University of Wisconsin and the other lead author of the report.

"If the situation improved for whatever reason, the child was thought to be allergic or intolerant of cow milk by the mother, thus promoting a myth of cow milk allergy/intolerance," Greer said.

About 3 percent of infants have milk allergies and most will outgrow them, according to the Nemours Foundation, a children's health care provider. A soy formula could be used in place of milk if an infant has an immune reaction to the cow milk protein.

But Greer said there is a 10 percent to 14 percent cross-reactivity between the proteins in cow milk and soy proteins, meaning that if you are allergic to cow's milk, there is a chance you will be allergic to soy, as well.

Instead of soy formula, pediatricians might prescribe a hydrolyzed cow milk formula for an allergic infant. In this kind of formula, the proteins are partially digested or broken down — enough so they will not elicit an immune response. But these formulas are prescription-only and can be more expensive than soy formula.

The simple solution would be to eliminate formula altogether and breast-feed, the gold standard for infant nutrition. The American Academy of Pediatrics and the U.S. Food and Drug Administration recommend breast-feeding exclusively for the first four to six months and then slowly introducing solid foods, continuing to breast-feed until the infant is about a year old.

But this regimen is not always possible, and here is where formula comes in. Because baby formulas are well developed and highly regulated, almost any formula will help infants grow and thrive.

"No one is ever going to be able to put breast milk in a can," said Dr. Russell Merritt, medical director and chief scientific officer for Abbot Nutrition, one of the companies that makes soy formulas. "Soy has a long history of use and is well integrated in pediatric practice. A lot of babies have benefited from it."

A Natural Formula

Lactose intolerance — an inability to digest milk sugars — is the major medical reason to use soy formula for an infant, according to the report, because soy milk has different sugars. Even so, lactose intolerance is rare in infants. Too rare, some think, to support the amount of soy formula consumed by the infant population.

The American Academy of Pediatrics estimates as much as 25 percent of the formulas on the market today are soy protein-based. Out of the 4 million children born in the United States each year, about a quarter of them are fed soy.

"The sale of soy infant formula is out of proportion for its perceived indications," Bhatia said. "You wouldn't do that with other things to babies — why would you do that to milk?"

Formulas, whether cow milk or soy, are still not without risk.

"In general, formula use is associated with increased illnesses, both infectious and chronic, like diabetes and cancers, and yet there is no warning on the label," said Dr. Miriam Labbok, director of the Center for Infant and Young Child Feeding and Care at the University of North Carolina at Chapel Hill. "We must begin to view formula as a risky choice for infant feeding, and do more to support women to succeed in breast-feeding."

The report from the American Academy of Pediatrics also referred to theories that some of the hormones in soy protein formulas can interfere with an infant's reproductive development because of their similarity to the human sex hormone estrogen. But no studies have supported these ideas.

Choosing cow milk formula, soy formula or breast-feeding ultimately comes down to personal preference, or, in a few cases, to medical necessity. But without any demonstrated benefit to soy formula for the average healthy infant, choosy pediatricians still choose cow milk.