by Amy Spangler
September 11, 2008

In a clinical report from the American Academy of Pediatrics (AAP) published in the May 2008 issue of Pediatrics and titled, “Use of Soy Protein-Based Formulas in Infant Feeding,” Jatinder Bhatia, MD and Frank Greer, MD review the “limited indications and contraindications of soy formulas and potential harmful effects of soy protein-based formulas and the phytoestrogens contained in these formulas.”

According to Bhatia and Greer, despite very limited indications for its use, soy formulas account for 20–25 percent of the U.S. formula market—perhaps indicative of a lack of understanding—perhaps reflective of the power of advertising.

While the benefits of breastfeeding for mothers and babies are widely understood, National Immunization Survey Data show that less than one-third of U.S. babies are exclusively breastfed for three months, despite the recommendation that babies be exclusively breastfed for six months.

Soy formulas have been in use for nearly 100 years. During that time, concerns have been raised about the ability of soy formulas to meet babies’ nutritional needs and the effects on infants and young children of phytoestrogens in soy formulas.

What do we know about soy protein-based formulas?
Soy protein comes from the soybean plant. Unlike animal protein, soy protein contains only five of the eight essential amino acids needed for growth, which explains why soy formulas are supplemented with methionine, carnitine, and taurine.

Most of the fat in soy formulas comes from vegetable oils such as soy, palm, sunflower, and coconut.

Soy formulas contain phytates, the salt form of phytic acid. Phytates bind with minerals, so soy formulas are supplemented with calcium and phosphorus to insure that babies’ mineral needs are met. Phytates also bind with iron and zinc, making them less bio-available, so iron and zinc are added to soy formulas as well. Kind of gives new meaning to the term, supplementation.

Phytoestrogens (isoflavones) are described by Bhatia and Greer as one of the many “heat-stable factors present in soy formulas.” Because phytoestrogens are similar in structure to steroidal estrogens, concerns have been raised about the effect of soy formulas on reproductive and endocrine function. In animal studies, when an individual component such as the isoflavone genistein was fed to mice, adverse effects were reported, but similar effects were not seen with the feeding of soy formula. After reviewing available data, Bhatia and Greer concluded, “…there is no conclusive evidence from animal, adult human, or infant populations that dietary soy isoflavones may adversely affect human development, reproduction, or endocrine function.”

As a parent, there’s something about the word “conclusive” that I find disturbing.

Last but not least, the authors discuss aluminum. The aluminum content of human milk is 4 to 65 ng/mL. Because mineral salts are used in the production of soy formulas, the aluminum content of soy formulas is 600 to 1300 ng/mL. According to Bhatia and Greer, “Because aluminum competes with calcium for absorption, increased amounts of dietary aluminum from isolated soy protein-based formula may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infant with intrauterine growth retardation. Term infants with normal renal (kidney) function do not seem to be at substantial risk of developing aluminum toxicity from soy protein-based formulas.”

As a parent, there’s something about the word “substantial” that I find disturbing, especially given that the level of aluminum in soy formula is approximately 200 times greater than that in human milk.

Recommendations for parents whose babies drink soy formulas
If your baby is among the very few for whom soy formulas are indicated and human milk (your milk or donor milk) is not available (no way, no how), then soy formulas may be the answer. But if your baby is among the 20–25 percent being fed soy formulas for non-medical reasons, you might want to discuss other options with your baby’s health care provider.

A summary of the clinical report follows:

• Soy formulas are seldom indicated for use in healthy, term babies. Two rare exceptions are babies with galactosemia or lactase deficiency. Also, babies, whose parents prefer to follow a strict vegetarian diet, may be fed soy formulas.

• Babies with proven cow milk protein allergy should be given hydrolyzed protein formula (partially digested formula) rather than soy protein-based formula, since 10 to 14 percent of these babies will have a soy protein allergy as well. Because hydrolyzed formulas taste nasty (and are pricey as well), some babies refuse them, so soy formulas may be the only alternative to human milk. Fortunately, the incidence of cow milk protein allergy is low (only 1 to 3 percent). What many people describe as cow milk protein allergy is actually not an allergy at all, but a food intolerance.

• Babies suffering from acute gastroenteritis (diarrhea) are encouraged to continue breastfeeding. Bottle-fed babies can be fed diluted cow milk formula if necessary, until the inflammation resolves.

• Soy formulas offer no advantage over cow milk formulas as a supplement for breastfed infants.

• Soy formulas are not intended for use in preterm infants.

• There is no evidence that routine use of soy formulas reduces the incidence of colic or fussiness or prevents allergic disease.

Instead of putting time and money into making better formulas, why don’t we invest in better support for breastfeeding mothers that includes (among other things) access to lactation care and services, extended maternity leave, flexible work schedules, and worksite centered child care. I can dream, can’t I?