Early, sustained introduction to cow’s milk protein inhibits allergy development
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Children who were introduced to cow’s milk protein early and consistently experienced a reduced risk for developing an allergy to it, according to a study published in The Journal of Allergy and Clinical Immunology: In Practice.
If exposure does not occur immediately after birth, tolerance is still possible if it happens 2 weeks to 6 months later, Karen M. Switkowski, PhD, MPH, principal associate in population medicine at Harvard Pilgrim Health Care, and colleagues wrote in the study.
“Cow’s milk allergy is among the most common food allergies in young children. Cow’s milk protein is often introduced before any other allergens or foods, in the form of cow’s milk-based infant formulas. In fact, many infants receive formula within days or hours of birth,” Switkowski told Healio.
The researchers were interested in studying how early exposure to milk formula could be related to later milk allergy symptoms, Switkowski continued, particularly considering research on peanut allergies that has led to new allergy prevention paradigms including early introduction to allergenic foods when infants are aged 4 to 6 months.
“We were interested in understanding whether the idea of ‘earlier is better’ also applied to cow’s milk, especially as that is frequently introduced to young babies through formula feeding,” Switkowski said.
Switkowski noted that a few recent studies have explored a similar question, but she and her colleagues had data on formula supplementation in the hospital after birth in addition to information about babies’ intake of infant formula or other cow’s milk-based products across infancy. This allowed the researchers to explore the interaction between those two factors in a novel way, she said.
The study’s design, results
The researchers studied 1,298 children who were part of the Project Viva prospective pre-birth cohort study of mother-child pairs, recruited between 1999 and 2002 during initial obstetric appointments at Atrius Harvard Vanguard Medical Associates in Massachusetts.
The study involved in-person visits with mothers and children in the hospital after delivery and during infancy as well as in early childhood, mid-childhood and early adolescence. Questionnaires were completed during each study visit and annually.
Mothers first introduced their children to cow’s milk protein within the first 2 weeks after birth (32%), between 2 weeks and 6 months (38%) or at 6 months or later (30%).
According to the study, 7.6% of these children had a cow’s milk adverse reaction (CMAR) at any time between age 2 and 13 years, with 5.3% reporting a CMAR in early childhood, defined as age 2 years to 5 years.
During early childhood, CMAR occurred among 3% of children with cow’s milk protein introduction within the first 2 weeks after birth, 5% of children with introduction between 2 weeks and 6 months, and 7.5% of children with introduction at 6 months and later.
Children with introduction at 6 months or later experienced twice the risk for CMAR at any time between age 2 and 13 years as those introduced within 2 weeks of birth (OR = 2.1; 95% CI, 1.2-3.7). This included odds ratios of 2.4 (95% CI, 1.2-4.7) in early childhood; 1.5 (95% CI, 0.7-3.5) in mid-childhood, defined as age 6 to 9 years; and 1.9 (95% CI, 0.7-4.9) in early adolescence, defined as age 10 to 13 years.
Also, children who did not receive a formula supplement at delivery but did have cow’s milk protein introduction within the first 2 weeks after birth were significantly more likely to develop a CMAR in early childhood compared with children who received both within the first 2 weeks (OR = 5.1; 95% CI, 1.6-16.2).
The researchers were surprised that babies who were given vs. not given formula in the hospital in the days after birth had different rates of later reactions to cow’s milk, Switkowski said.
“Babies who did get formula in the hospital just after birth had the lowest risk of developing adverse reactions to cow’s milk, but only if they continued to receive a cow’s milk-based formula within the 2 weeks after birth,” she said.
“Among babies who didn’t get any formula just after birth, the best time to introduce cow’s milk protein seemed to be later — sometime between 2 weeks and 6 months,” Switkowski continued.
However, IgE measurements did not reveal any association between timing of cow’s milk protein introduction and and serum evidence of sensitization to milk or IgE-mediated milk allergy.
Risk for CMAR also did not appear influenced by parental history of atopy, partially or fully breastfeeding, and use of soy-based or hypoallergenic (hydrolyzed) formula.
Next steps
These findings can serve as a reminder that providing supplemental formula immediately after birth may potentially increase the risk for milk allergy among babies who then are exclusively breastfed once they leave the hospital, Switkowski said.
“On the other hand, babies who continue to get some formula and some breastmilk during the first 2 weeks of life may not be at higher risk,” she added.
Further, Switkowski said that doctors can use these findings to support recommendations that parents should introduce cow’s milk-based dairy products to their baby, along with other complementary and potentially allergenic foods, between 4 and 6 months of age.
“In fact, in our overall study population, first introducing cow’s milk protein beyond 6 months was associated with the highest risk of later adverse reactions to cow’s milk,” she said.
Next, the researchers hope to explore the impact of the mother’s diet during pregnancy and, if she is breastfeeding, during lactation on the baby’s tolerance of cow’s milk and other food allergens.
“We also plan to examine timing of introduction of other food allergens in relation to later adverse food reactions among babies with different types of feeding,” Switkowski said.
For more information:
Karen M. Switkowski, PhD, MPH, can be reached at karen_switkowski@harvardpilgrim.org.