Side Effects of Soy Infant Formula

There are few alternatives available to infants who are allergic to cow's milk and are not breastfed. One popular dairy-free formula alternative is soy formula, but is soy a good choice for babies who cannot assimilate cow's milk? There are pros and cons to consider when choosing soy-based formulas. Knowing what the side effects can be will help a mother make a more informed decision on the best formula for her baby.


Soy contains certain anti-nutrients, called protease inhibitors, that can cause poor growth and digestive problems.

Saponins and Lectins

Saponins and the lectins naturally found in soy can cause gastrointestinal difficulties and leaky gut. Saponins and lectins can also create a weak immune system.

Oligosaccharides and Colic

The oligosaccharides present in soy are what create increased gas production, which can lead to colic in babies.

Vitamin Deficiencies

The American Academy of Pediatrics recommends that soy not be used as a sole source of nutrition for infants, because of the attendant risk of a deficiency in zinc and calcium.

What Soy Won't Help

The American Academy of Pediatrics has revised its views on soy formula, based on research alleged to have shown that soy formulas actually have the same effect on infants who have difficulty digesting cow's milk--thus making formula an ineffective substitute. The AAP also states that preterm infants, infants with allergies to cow's milk, and colicky infants are not good candidates for soy formula.

When Soy is the Right Choice

According to the AAP, soy formula is a good choice for infants who cannot convert galactose into glucose--a condition known as congenital galactosemia.

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