Last updated: Sep 21, 2016

When babies eat certain foods early in life—the kinds so many end up allergic to, like eggs and peanuts—they’re less likely to develop allergies to those foods later on, finds a new analysis published in the Journal of the American Medical Association (JAMA).

This is relatively new thinking. Not so long ago, in 2000, the American Academy of Pediatrics recommended that allergenic foods be kept away from infants until they were at least a year old, and often older. That warning was especially strong for those with a family history of allergies. But, as an editorial published in the same issue of JAMA points out, in the next decade, food allergy prevalence nearly doubled in the United States.

That advice has been amended, and newer evidence has shown that introducing foods earlier is actually better for preventing food allergies. The authors of the just-published study reviewed all of the available evidence on the topic and included 146 studies in their final analysis.

They found evidence of “moderate certainty” that introducing peanuts early, between ages 4 and 11 months, is linked to a reduction in the risk of developing a peanut allergy. Eggs, too, showed this association when they were introduced between ages 4 and 6 months. Early introduction of another common allergen, fish, was also linked to less allergy—possibly due to the anti-inflammatory effects of omega-3s—though evidence for this link wasn’t as certain.

Early introduction didn’t seem to make a difference for autoimmune diseases, at least according to the available evidence; eating gluten young wasn’t associated with the risk of developing celiac disease.

Exactly why is a question researchers are still exploring. “It is not clear that it is the specific early introduction of an allergenic food that renders immunological protection, rather than the accompanying increased diversity in the diet that occurs as a by-product,” writes Dr. Matthew Greenhawt, an allergy and immunology specialist at Children’s Hospital Colorado, in the accompanying editorial. More research is necessary to figure out the ideal amounts of these allergens, the optimum times of introduction and the reasons behind the link.

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