July 22, 2004 -- Soy-based formulas are often recommended for infants with food allergies, but a review of past studies suggests they should not be recommended for the prevention of allergies or food intolerance in infants at high risk.
Although the evidence is not conclusive, the review suggested that formulas designed for infants with food allergies are a better choice for preventing allergies than soy-based formulas. At least one study comparing the use of these "hydrolysate" formulas with those containing soy found that the soy-fed babies were significantly more likely to develop allergies and eczema.
"Feeding with a soy formula should not be recommended for the prevention of allergy or food intolerance in infants at high risk (for these conditions)," researchers from the Westmead Hospital in New South Wales, Australia, write in the latest issue of The Cochrane Library Newsletter.
Breast Is Best
Four percent to 6% of children have food allergies, and a close family history is the best predictor of risk. A child that has two parents with food allergies has about a 75% chance of also developing allergies herself.
Although the researchers did not review studies that included breastfed babies, pediatric allergy experts contacted by WebMD say the best clinical evidence suggests that breastfeeding is by far the best choice for high-risk babies.
The American Academy of Pediatrics strongly recommends "exclusive breastfeeding as the hallmark for food allergy prevention" for at least six months. It further states that breastfeeding should continue for at least a year, although other foods should also be introduced after the sixth month.
"The best evidence that we have suggests that breastfeeding can help prevent food allergies in children at high risk," New York allergist Clifford Bassett, MD, tells WebMD. Bassett is a spokesman for the American Academy of Allergy, Asthma & Immunology.
In a joint report published last summer, the AAP and two European health groups addressed the issue of soy-based formulas vs. cow's milk-based formulas for preventing food allergies. The group noted that "studies of soy versus cow milk formula feeding in infants ... have not shown any prevention effect of soy on food allergy or atopic dermatitis." It concluded that there is "insufficient evidence to recommend soy formula feeding for primary food allergy prevention."
Soy-based formulas contain the proteins found in soybeans rather than those found in cow's milk. The two formulas contain almost identical vitamins and minerals, and their nutritional values are similar.
There are three major hypoallergenic formulas:
- Whey-based hydrolysate formulas. The whey in cow's milk protein is broken down or "predigested," making it less allergenic than the protein in regular formulas.
- Casein hydrolysate formulas have smaller protein products.
- Amino acid-based infant formulas, which contain protein in its simplest form, may be recommended if an infant doesn't improve after a switch to the hydrolysate formulas.
Among the other recommendations:
- High-risk mothers-to-be should not eat peanuts or foods containing peanuts during pregnancy. While the evidence linking maternal peanut consumption to infant allergies is not conclusive, the group singled out peanuts as the food most likely to cause problems, and it suggested that lactating mothers avoid them as well.
- Delay the introduction of solid foods for six months, and delay the introduction of potential problem foods for as long as possible. The AAP recommends delaying the introduction of cow's milk until 12 months of age, eggs until 24 months, and nuts and fish until age 3.
- Protein hydrolysate formulas should be used in bottle-fed, high-risk infants.
Pediatric allergy expert Mary Fasano, MD, says she recommends hydrolysate formulas for bottle-fed, high-risk infants, even though they have not been proven to prevent allergies or delay their onset. Fasano is an associate professor of clinical medicine at the University of Iowa and a spokeswoman for the AAP.
"The strongest evidence for protection is clearly for breastfeeding, so that will always be my first recommendation," she says. "There just is not a lot of good, strong evidence to show that hydrolysate formulas prevent allergies."