Early solid foods tied to lower peanut allergy risk

NEW YORK Thu May 5, 2011 2:35pm EDT

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NEW YORK (Reuters Health) - Infants with a family history of allergies might be less likely to develop a peanut allergy if they start solid foods before the age of four months, a new study suggests.

Researchers found that among 2- and 3-year-olds whose parents suffered from allergies, those who were started early on solid foods or cow's milk were about five times less likely to be sensitized to peanuts.

"Sensitized" means that a child has immune-system antibodies directed at a potential allergen -- in this case, peanut proteins -- and is at increased risk of having a full-blown allergy to that substance.

Still, the findings do not prove that early introduction of "complementary" foods prevents peanut allergies, said Christine Joseph, the lead researcher on the study and an epidemiologist at the Henry Ford Health System in Detroit.

The study, she told Reuters Health, shows an association, but cannot prove cause-and-effect.

So it's too early to make any recommendations to parents on when to introduce solid foods or cow's milk, Joseph said.

And in general, she noted, there is controversy over which infant feeding tactics, if any, might cut the risk of food allergies.

At one time, the American Academy of Pediatrics recommended that parents not give children cow's milk until after their first birthday, eggs until the age of two, or peanuts until age three. But the group reversed that position in 2008, after studies showed no good evidence that the advice lowered kids' food allergy risks.

Right now, experts generally recommend that infants be breastfed exclusively for the first six months of life because it is the best form of nutrition. Whether that has any benefit on food allergy risks, though, remains unclear.

The new findings are based on 594 children whose mothers were interviewed when the children were one, six, and 12 months old. When the children were 2 to 3 years old, the researchers tested their blood samples for antibodies against peanut, egg and milk -- three common triggers of childhood food allergies.

Overall, 11 percent of the children were sensitized to peanut. Among children whose parents had allergies or asthma, the risk of peanut sensitization was lower if they'd been started on solid food or cow's milk before the age of four months.

Of those children, just under 6 percent had peanut sensitivity, versus 16 percent of those who'd had the foods introduced later in infancy. That corresponds to a five-fold difference in risk, after taking into account other things that might set the toddlers up for allergies.

There was no similar pattern among children whose parents were allergy-free.

It's too early to tell whether early solid foods are a "good thing" for infants with a family history of allergies, Joseph said.

"Intuitively, it does seem like the opposite of what you'd expect," she noted.

However, Joseph explained, for infants with a genetic susceptibility to allergies, early exposure to a broader range of foods could be the "kick start" needed for immune-system cells in the gut to mature.

And that, in turn, could make them less likely to develop food allergies later in childhood.

Joseph said that larger studies are needed to confirm the current findings. Lab research would also be helpful to see exactly why early introduction of solid foods and cow's milk might protect against peanut sensitization.

Also unclear, she added, is why this study found a lower risk of peanut sensitization only, and not egg or milk sensitization.

Peanut allergies do tend to be more severe than milk or egg allergies, Joseph pointed out, but it's not certain if that is a reason for the findings.

It's estimated that just over one percent of U.S. children are allergic to peanuts, but that rate appears to have been on the rise over the past couple decades. No one is sure why.

SOURCE: bit.ly/jBbFw8 Journal of Allergy and Clinical Immunology, May 2011.

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