The Peanut Trap


You know, there are times when the cart should precede the horse and not follow blindly behind it along the same old paths. We are too often seduced by the roads that others have made simply because we know where they go and what we might reasonably expect to encounter along the way. The problem, of course, is that another reasonable expectation of taking the same route is ending up in the same place.

Sometimes the detours that others have taken, whether through ignorance or design, have ended up in far more interesting places. More significant destinations. We might do better if it was them we followed, not the horse.

Childhood allergies have always puzzled me: are they all genetically determined, or is there something else going on? Because their prevalence seems to be increasing –especially peanut allergy. As an editorial in The New England Journal of Medicine (Feb.26/15) suggests: ( http://www.nejm.org/doi/full/10.1056/NEJMe1500186 ) ‘In the United States alone, the prevalence has more than quadrupled in the past 13 years, growing from 0.4% in 1997 to 1.4% in 20081 to more than 2% in 2010. Peanut allergy has become the leading cause of anaphylaxis and death related to food allergy in the United States.’ But why?

As the editorial goes on to say: ‘In 2000, largely in response to outcomes reported in infant feeding trials conducted in Europe and the United States, the American Academy of Pediatrics (AAP) recommended that parents refrain from feeding peanuts to infants at risk for the development of atopic disease until the children reached 3 years of age.’ And yet despite that, the number of cases of peanut allergy still continued to rise…

So, ‘In 2008, after reviewing the published literature, the AAP retracted its recommendation, stating that there was insufficient evidence to call for early food avoidance.’

Then, a fortuitous observation: ‘Du Toit et al.6 noted that the prevalence of peanut allergy among Jewish children in London who were not given peanut-based products in the first year of life was 10 times as high as that among Jewish children in Israel who had consumed peanut-based products before their first birthday. In addition, subsequent studies that evaluated the early introduction of other allergenic foods, including egg7 and cow’s milk,8 showed that earlier introduction of egg and milk into an infant’s diet was associated with a decrease in the development of allergy.’ A different path.

The subsequent study, known as LEAP (Learning Early About Peanut allergy), was a truly courageous and, dare I say, a lodestar one: http://www.nejm.org/doi/full/10.1056/NEJMoa1414850

The investigators hypothesized that early introduction of peanut-based products (before 11 months of age) would lead to the prevention of peanut allergy in high-risk infants. More than 500 infants at high risk for peanut allergy were randomly assigned to receive peanut products (consumption group) or to avoid them (avoidance group). Approximately 10% of children, in whom a wheal measuring more than 4 mm developed after they received a peanut-specific skin-prick test, were excluded from the study because of concerns that they would have severe reactions. At 5 years of age, the children were given a peanut challenge to determine the prevalence of peanut allergy. The results are striking — overall, the prevalence of peanut allergy in the peanut-avoidance group was 17.2% as compared with 3.2% in the consumption group.’ As a result, the study found that ‘the early introduction of peanut dramatically decreases the risk of development of peanut allergy (approximately 70 to 80%).’ The immune system –and what it considers ‘foreign’ and hence dangerous- develops early in life. Early exposure to something may therefore render it more acceptable –not an allergen…

But, as in all scientific inquiries, one has to be careful not to generalize the results too liberally. Perhaps, despite all their precautions to be representative and mindful of conditions that may differ among populations sampled for the study, it may not obtain universally. For example, the editorialist points out: ‘Should we recommend introducing peanuts to all infants before they reach 11 months of age? Unfortunately, the answer is not that simple, and many questions remain unanswered: Do infants need to ingest 2 g of peanut protein (approximately eight peanuts) three times a week on a regular basis for 5 years, or will it suffice to consume lesser amounts on a more intermittent basis for a shorter period of time? If regular peanut consumption is discontinued for a prolonged period, will tolerance persist? Can the findings of the LEAP study be applied to other foods, such as milk, eggs, and tree nuts?

All good questions –and ones, it should be noted, that troubled the authors sufficiently that they have designed a followup study to assess: ‘The question of whether the participants who consumed peanut would continue to remain protected against the development of peanut allergy even after prolonged cessation of peanut consumption requires further study and is under investigation in the LEAP-On study (Persistence of Oral Tolerance to Peanut; ClinicalTrials.gov number, NCT01366846).

I am impressed with the study because of the determination of the investigators to journey down a road not well travelled -in this case the sure and certain one that Society had come to believe: that you should avoid all possible allergens from birth or risk irreparable damage to your child. Once something has been generally accepted, to transgress, to wander from the road, is anathema. Folkways have a habit of becoming incontrovertable Laws. Unexaminable tenets. Incontestable. Indisputable.

We humans are like that: we follow the horse because it’s easy. And if the route it takes is falling into disrepair, we merely shrug because we know we are on the road we are supposed to be on. The one everybody knows is safe… But it is a trap -almost like that apocryphal conditioning experiment with pigeons: when one happened to turn around a few times before the food arrived, it continued to do so each time before it got fed… Why take any chances?

In the case of allergens, it seems less silly, though. Less arbitrary. If one child develops a severe allergy to, say, peanuts, most people would feel it would be reasonable to avoid exposing the next child to peanuts. It may not work, but why take any chances? To do any different would be madness. Everybody would agree with that…

I am reminded of something Mark Twain once said: ‘Whenever you find yourself on the side of the majority, it is time to pause and reflect.’ There is, no doubt, a degree of wisdom in the crowd, but we must beware conflating the wisdom of our crowd, with its blindness.

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