Newswise — Although soy infant formulas were created to reduce the chances of babies developing allergies or food intolerances, there is no clear proof that soy or other specialized formulas lower those risks, a new review has found.

"There is no evidence that using any type of formula is better than exclusive breastfeeding for prevention of allergy," said authors David Osborn, M.D., of Royal Prince Alfred Hospital and John Sinn, M.D., of Westmead Hospital, in Australia. "Specialized formulas should be restricted to situations where infants cannot exclusively breastfeed or when an infant develops a specific food allergy or hypersensitivity."

Food allergies can include wheat, peanuts, cow's milk and soy protein. Cow's milk allergy is the most prevalent in children and has been documented in 1.8 percent of children along with 0.5 percent of children who have allergies to soy protein, the reviewers say.

Mothers who do not breastfeed introduce their infants to cow's milk or soy formula early in life, which has been linked to an increased chance of the newborn developing allergy or food intolerance. In an effort to combat these risks, infants are often prescribed formulas such as hydrolyzed cow's milk, adapted soy and hydrolyzed soy formula.

The aim of the systematic review was to determine whether soy infant formulas do indeed prevent allergy and food intolerance, and whether they are linked to any particular benefits or harms to an infant's growth and development.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates research in all aspects of health care. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing trials on a topic.

The Cochrane reviewers analysed three studies that compared formulas for prolonged infant feeding. The enrollment size of each was considered small β€” with the combined number of infants totaling 875.

Reviewers did not include studies of infants already diagnosed with food allergies or food intolerances; instead, review studies evaluated infants considered at high risk of allergies based on a strong family history β€” infants whose parent or sibling had ever had a significant allergy.

The studies followed these infants into childhood up to 10 years of age to determine if they had developed allergies or intolerances.

Based on the results, the authors concluded there was no significant benefit from the use of a soy formula compared to a cow's milk formula.

The review supported previous evidence that mothers who choose to only breastfeed their infants for at least six months do reduce the incidence of allergy.

According to the American Academy of Pediatrics, women who don't have health problems should "exclusively breastfeed their infants for at least the first six months of life."

Breast milk provides the right balance of nutrients to help an infant grow into a strong and healthy toddler, according to the National Institute of Child Health and Human Development, and some of the nutrients in breast milk also help protect against some common childhood illnesses and infections.

Despite these benefits, many mothers still introduce their babies to cow's milk or soy milk formula, which some nutritionists believe may not be an acceptable substitution.

"I personally do not advocate soy milk," said nutritionist Susan M. Mudd, M.S., of Body Tech in Gaithersburg, MD. "Soy milk is a high allergen and previous soy-based infant formulas have actually been linked to impaired thyroid function and an extremely high amount of estrogen in some babies."

However, Osborn says that those specific problems were reported "for some soy formulas that had high iodine contents β€”it is probably not the case with current ones." Nevertheless, "I would advise mothers to be careful of the risks," Mudd said. "I'd tell them to ask their doctors about soy milk and conduct their own research before making a decision to put their infants on a soy diet."

Osborn DA, Sinn J. Soy formula for prevention of allergy and food intolerance in infants. Cochrane Database of Systematic Reviews 2006, Issue 4.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit for more information.

Register for reporter access to contact details

Cochrane Database of Systematic Reviews