Is soy-based formula better than cow’s milk formula?

Soy-based formulas were developed as an alternative food source for infants who didn’t have access to human milk and couldn’t tolerate cow’s milk protein. Soy-based formula was first released in 1929, but it wasn’t until federal regulations were introduced in 1971 that it gained acceptance. Soy formulas currently represent an estimated 40 percent of U.S. formula sales, even though the American Academy of Pediatrics (AAP) recommends that it be used only in rare instances, such as for infants with the galactosemia, a genetic condition which makes it impossible for a child to metabolize galactose, one of the two sugars in lactose. 

Soy’s popularity is largely tied to a growing awareness of food allergies (particularly dairy) and lactose intolerance. Some parents who choose to formula-feed want to avoid giving their baby cow’s milk-based formula—hoping this will reduce their child’s risk of developing allergies. However, nearly half of all babies who are allergic to cow’s milk protein are also allergic to soy protein, and there is no evidence that avoiding a cow’s milk-based formula in infancy will reduce the child’s risk for dairy allergy. 

For infants who have been diagnosed with a cow’s milk allergy, several options are available and should be discussed with your child’s pediatrician. Previously, the American Academy of Pediatrics (AAP) recommended a specialized infant formula made with hydrolyzed (extensively or partially digested) cow’s milk proteins. Now, the Food and Drug Administration (FDA) warns against the use of hydrolyzed formulas for food allergy, noting that “partially hydrolyzed formulas should not be fed to infants who are allergic to milk or to infants with existing milk allergy symptoms.” The FDA also ruled that manufacturers of such formulas must include a warning statement that partially hydrolyzed formulas are not hypoallergenic and should not be fed to infants who are allergic to milk or have existing milk allergy symptoms. While amino acid formulas may be appropriate for severe cases and lactose-free formulas may be helpful for infants with difficulty digesting lactose, this condition is rarely seen in infants and is more common in older children and adults. 

Some parents select soy-based formula because they believe manufacturers’ claims that it is gentler on babies’ stomachs than milk-based formula. These claims are unsubstantiated by medical studies. In fact, some researchers suggest that the common but controversial infant formula additives docoahexaenoic acid and arachidonic acid (DHA and RHA) may, in fact, lead to gastrointestinal upset. What’s more, concerns have been raised about the risks of soy-based formula for the reproductive system. Soy-based formulas contain estrogen-like substances, called phytoestrogens, which may affect hormonal development. 

There’s no doubt that experts agree the “best” nutrition for babies is human milk. The AAP continues to recommend that infants be exclusively breastfed for the first six months of life, and that breastfeeding continue, along with age- appropriate complementary foods, until a child is at least 1 year of age. Parents concerned about food allergies should take note that, according to the AAP, for children with “a strong family history of allergies,” breastfeeding may help to reduce the infant’s risk of food allergies. 

If you choose to formula-feed—exclusively or in conjunction with breastfeeding—be sure to choose your baby’s formula carefully. Unless your child’s pediatrician specifically recommends soy formula, you may want to consider a cow’s milk-based formula. 

For more information about infant formulas, see our guidance about iron-fortified formula and ready-to-feed versus powdered formulas, as well as the AAP’s “Choosing a Formula” recommendations.

Last updated February 10, 2020

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