It has become an article of faith among many of my friends that when they're pregnant, they should eliminate foods that could lead to allergies in their children.  They forego shellfish, they do without dairy, but most importantly, they avoid peanuts.  This behavior continues after their children are born.  While they're breastfeeding, they continue to abstain from certain foods.  They certainly keep their children themselves from eating them.

But research in the last few years has consistently shown that this may be the wrong approach.  We may be doing more harm than good with all this avoidance.  We might want to consider doing the opposite.  That's the topic of this week's Healthcare Triage.

(Intro)

Mothers didn't adopt this behavior out of nowhere.  A debate's been raging in the healthcare system for decades on this topic.  In 2000, the American Academy of Pediatrics released guidelines for reducing a child's risk for developing allergies.  They recommended that, and I'm quoting, "Mothers should eliminate peanuts and tree nuts, or almonds, walnuts, etc, and consider eliminating eggs, cow's milk, fish, and perhaps other foods from their diets while nursing."  Further, they recommended that kids at high risk for allergies be given no solid foods until six months of age, no dairy products until one year, no eggs until two years, and no peanuts, nuts, or fish until three years.

Mothers disagreed.  Along with colleagues, I was part of a systematic review that examined the relationship between early solid food introduction and allergic disease in children.  We found no good evidence to support the idea that being exposed to solid foods earlier led to persistent food allergies.  

To its credit, the AP changed its recommendations based on that research.  In 2008, they updated guidelines to report that maternal restrictions in pregnancy or breastfeeding no longer seem like advice that should be widely recommended.  They also acknowledged that there didn't seem to be much reason to delay the introduction of allergy foods like peanuts after six months.

Unfortunately, this did little to change peoples' behavior.  Many had already internalized the advice.  It seemed logical to them that avoiding foods would give kids less of a chance to develop allergies.  If it was still a good idea not to expose kids until they were six months old, why not keep going?

A study published in the New England Journal of Medicine last year, which we've covered, turned all this on its head.  Researchers enrolled 640 high risk infants, before four and eleven months of age, in a trial and randomized them to one of two groups.  One of them was told to avoid peanut protein.  The other was told to eat at least six grams of peanut protein a week given in three or more meals and participants were followed until they were five years old. 

What was most surprising in this work was that 15% of the infants already had evidence of peanut sensitivity by allergy testing, and they were still enrolled in the trial, and half of them were given peanut extract every week.  The results were remarkable.  At the end of the trial, about 3% of those exposed to peanuts had developed a peanut allergy, compared to more than 17% of those who avoided peanuts.  More surprising, if you looked just at the kids who already had evidence of peanut sensitivity as infants, fewer than 11% of those who'd been exposed to peanuts regularly developed an allergy compared to more than 35% of those who avoided peanuts.

Children who had a proven sensitivity to peanuts but consumed them in their diet regularly were less likely to develop a peanut allergy than kids without sensitivity but who avoided them.  Recently, follow-up results were published.  After the trial ended, researchers asked all the participants to avoid peanuts for the next 12 months.  Att the end of that period, when the kids were like, six years of age, there were no longer any differences in the development of new peanut allergy in the previously defined groups.

This meant that after four years of peanut exposure, further consistent exposure was no longer necessary to maintain health.  The critical time of intervention appears to be somewhere from infancy until five years of age.  These results were so convincing that once again, experts are changing their recommendations.  In September of last year, the AAP, along with others, argued that, and I'm quoting, "Healthcare providers should recommend introducing peanut containing products into the diets of high-risk infants early on in life."  

These changes dovetail nicely with what has become known as the hygiene hypothesis, the gist of which is that as we've made our environment more and more sterile, our immune systems develop differently than they used to.  Without exposure to outside things to fight, our defenses turn inwards and towards more benign substances, leading to increased levels of eczema, asthma, and allergies.  

Of course, many people used to die from infections that no longer do because of advances, so no one should take this as a call for less safe environments, nor should anyone take these recent findings as advice to feed babies and small children peanuts and other foods without concern.  All changes to a child's diet, especially children with allergies, should be done in consultation with a healthcare professional.

As with many things in healthcare, however, we may have gone too far with our response to peanut and other food allergies.  Avoidance is sometimes needed for those with severe reactions.  When we apply those same rules to everyone else, however, things may backfire.

Healthcare Triage is supported in part by viewers like you through patreon.com, a service that allows you to support the show through a monthly donation.  We'd especially like to thank our research associate Joe Sevits and our surgeon admiral Sam.  Thanks, Joe! Thanks, Sam!  More information can be found at patreon.com/healthcaretriage.