Marketers advise parents that soy-based, lactose-free formulas help to alleviate colic, constipation, diarrhea, and allergies. In spite of limited evidence for these claims, such advertising—and consequent word-of-mouth networking—accounts for the fact that soy formulas comprise nearly 25% of formula sales in the US. (Bhatia J, Greer F. Use of soy protein-based formulas in infant feeding. Pediatrics 2008;121(5):1062-68)
Although most experts recommend breastfeeding for optimal infant nutrition, many parents choose formula as an acceptable replacement or supplement for breast milk. However, parents and healthcare professionals alike can be perplexed by the array of available formulas.
Infant formulas are classified according to three basic criteria: protein composition, a carbohydrate source, and caloric density.
Because soy formulas are made with soy protein and corn-based carbohydrate—rather than cow’s milk protein and lactose—many parents choose soy-based products, assuming that such formulas are more easily digested and less likely to contribute to food allergies.
Many Claims of Soy Formula Benefits Are Overstated
- According to the American Academy of Pediatrics, there is little evidence of benefit from soy formula in conditions such as milk-protein allergy, colic, or acute gastroenteritis. (O’Connor N. Infant formula. Am Fam Phys 2009;79(7):565-70)
- Soy formula is not effective for the prevention of atopic disease (allergies). (Osborn D, Sinn J. Formulas containing hydrolysed protein for prevention of allergy and food intolerance in infants. Cochrane Database Syst Rev 2006;(4):CD003664)
- Although soy formula may shorten the duration of diarrhea in acute gastroenteritis (“stomach flu”), it does not impact overall recovery. While temporary lactase deficiency may occur during such an illness—making lactose digestion more difficult—soy and other lactose-free formulas do not change the overall course. (Allen U, et al. Cow’s milk versus soy-based formula in mild and moderate diarrhea: a randomized, controlled trial. Acta Paediatr 1994;83(2):183-87)
- Although a lactose-free formula is often suggested for an infant with persistent gastrointestinal symptoms, true lactose intolerance is over-diagnosed in infancy. Most proven cases occur after one year of age. (Heyman M. Committee on Nutrition. Lactose intolerance in infants, children, and adolescents. Pediatrics 2006;118(3):1279-86)
- Soy formulas should not be used for preterm infants; they lead to inadequate weight gain and contribute to decreased bone density in this population. (Hall R, et al. Comparison of calcium- and phosphorus-supplemented soy isolate formula with whey-predominant premature formula in very low birth weight infants. J Pediatr Gastroenterol Nutr 1984;3(4):571-76 and Callenbach J, et al. Etiologic factors in rickets of very-low-birth-weight infants. J Pediatr 1981;98(5):800-805)
- Milk allergy is not an indication to use soy formulas since most infants with a bona fide milk allergy are equally sensitive to soy proteins. (Bhatia J, Greer F. Use of soy protein-based formulas in infant feeding. Pediatrics 2008;121(5):1062-68)
Indications for Using Soy Formulas
In reality, soy-based formulas need only be considered in three situations:
- Infants with galactosemia (a rare genetic disorder in which galactose—a byproduct of lactose metabolism—cannot be further broken down. This leads to a toxic buildup of galactose in various tissues and organs in the body)
- Infants with congenital lactase deficiency (an absence of the enzyme that breaks down lactose, or milk sugar)
- Infants whose families are strict vegans and who wish to avoid animal-based products
In the absence of specific medical conditions or ethical considerations that indicate their use, soy-based formulas do not offer any clear advantage over cow’s milk-based formulas.