Data collected on 2,100 kids in the Canadian Healthy Infant Longitudinal Development (CHILD) study showed that infants who avoided cow’s milk or products like yogurt in the first year of life were almost four times more likely to become sensitized to milk compared to those as those who consumed a form of dairy.
For egg and peanut, the risk of developing sensitization to either of these foods was twice as high among babies avoiding these foods in the first 12 months. (While sensitization may be outgrown, it can also be the precursor to a full-blown allergy.)
“I think the evidence is consistent with the hypothesis that introducing early is more likely to result in tolerance, and avoiding the food may lead to not developing tolerance,” said Dr. Malcolm Sears, co-director of CHILD and a professor of medicine at McMaster University in Hamilton, Ontario.
The egg findings are particularly interesting, as the evidence on egg exposure versus avoidance have not been as clearly protective against allergy as the results for early peanut exposure, with the latter strongly shown in the groundbreaking LEAP and LEAP-On studies. As well, the new CHILD research, published in the journal Pediatric Allergy and Immunology, revealed that tolerating egg before the first birthday carries more benefits than just the safe consumption of egg-containing food.
“From a general population view, early introduction of egg was certainly associated with a reduced likelihood of sensitization, not only to egg but also to the other two foods (milk and peanut), Sears said in an interview with Allergic Living. While LEAP looked at the onset of peanut allergy in an infant population at high risk for allergies, the CHILD study has been tracking the onset of allergies and asthma in children within a general population cohort.
For the milk findings, Sears says most cow’s milk was consumed in the form of formula, and kids who got it earlier were significantly less likely to develop milk allergy. Sears says that breastfeeding is “clearly good for many, many reasons. But adding complementary feeding while continuing breastfeeding may be even better.” He says the CHILD team will have more to report on this later by early next year.
He stresses an important caveat to the benefits of early feeding of these foods: “In children, who early on, develop severe sensitization to egg or cow’s milk, then clearly the only strategy is avoidance.”
Infant feeding of known allergenic foods is still not common practice. In the CHILD study, only 3 percent of parents introduced egg before six months of age, and 63 percent avoided feeding peanut in the first year of life.
One of the issues the CHILD group has been grappling with is whether egg exposures may be occurring through household dust. This type of exposure has been seen in studies with peanut, with young children being exposed to peanut through household dust, even if they’ve never been near a peanut or peanut butter. “We think it’s important, the actual food being processed through the gut, and the processes there, resulting in the stimulation of immune tolerance,” says Sears.
The epidemiologist and respiratory expert notes that the oldest children in the CHILD study, who’ve been tracked for allergy symptoms since birth, are starting to turn 8 years old. Sears hopes to be able to maintain funding for the project, which is currently through the AllerGen Network and a Canadian government agency. “We’ve learned a lot in the first five years,” Sears says, but he’d like the children to be followed until the age of 14 so the research team can consider hormonal effects before and after puberty on allergies.