The other day I stumbled upon “The Peanut Puzzle,” an article from The New Yorker (where I worked as a fact-checker in the 1990s) that was published last February and that somehow I had missed. Written by Jerome Groopman, a prominent cancer and AIDS researcher and professor of medicine at Harvard Medical School who also happens to be a gifted magazine journalist, it’s one of the most sober, cogent and engaging pieces of writing about peanut allergy, and the latest thinking about its origins, prevention and treatment, that I’ve come across yet. If you’re curious about peanut allergy, and/or are caring for a child diagnosed with the disorder, and you haven’t read Dr. Groopman’s story, you really should. For those of you who aren’t subscribers and don’t have access to the magazine’s online archive, I’ve uploaded it at the link below:
If you don’t have time to read the article (it’s five pages long), I’ll do my best to distill it here:
Dr. Groopman’s narrative revolves around Dr. Hugh Sampson, director of the Jaffe Food Allergy Institute at Mt. Sinai Medical Center in New York City. If that name sounds familiar to those of you who are following this blog, it’s because Dr. Sampson is the physician Dr. Mary Tobin was referring to in my April 2 post, “A Kid’s Life is Worth More than a Peanut Butter Sandwich.” Like most physicians, until recently, Dr. Sampson believed that the best way to protect at-risk children from developing food allergies was to shield them from exposure to peanuts and other proteins known to trigger allergies while in the womb, and during infancy, the idea being that a child’s immune system needed time to mature in order to recognize that these suspect foods were in fact benign and are not harmful to the system. Based on this assumption, in 2000, the American Academy of Pediatrics adopted guidelines that urged mothers of at-risk children to avoid eating allergenic foods during pregnancy and while breastfeeding and delay the introduction of these foods into the child’s diet, an instruction pediatricians nationwide passed on to thousands if not millions of expectant and nursing mothers who dutifully followed that dietary advice, wanting to do what was best for their babies. But recently, Dr. Groopman writes, the experts have made a dramatic about face: “Sampson and other specialists believe that early exposure [to peanuts and other allergenic foods] may actually prevent food allergies.” Noting that Sampson and another Mount Sinai pediatric allergist have documented a dramatic rise in food allergy diagnoses over the past decade–estimating that three to five percent of the population now is allergic to milk, eggs, peanuts, tree nuts or seafood, and that over the past decade, allergies to peanuts have doubled–Groopman leads the reader to the obvious conclusion: the policy of avoidance that the American Academy of Pediatrics embraced in 2000 may have unintentionally exacerbated, if not induced, the very condition it was supposed to circumvent.
Why the sudden reversal? It helps to understand the mechanism at work here, the proteins that are at the heart of food allergy.
Groopman explains that the proteins found in the eight foods that most commonly trigger allergic reactions–eggs, milk, peanuts, tree nuts, fish, shellfish, wheat and soy–all have one thing in common: unlike most other foods, these proteins don’t readily break down when exposed to heat (during cooking) and stomach acid (during digestion). It’s this breakdown resistance that causes the body to recognize an otherwise benign food, like a peanut or milk, as a potentially harmful foreign substance. This in turn causes the body to produce large amounts of antibodies known as Immunoglobulin E, or IgE; in food allergy diagnoses, it’s the amount of IgE in a patient’s blood that determines the severity of the allergy. You can think of IgE antibodies as the foot soldiers of the immune system, the first line of defense in fighting off foreign invaders; when the body senses danger, it musters an army, which lies in wait for the next invasion. So when the rogue protein appears again in the bloodstream, the antibodies attack, waging an all-out war. The IgE molecules attach themselves to the peanut protein (or milk, soy, egg etc.), which triggers the release of histamine and other chemicals that initiate the classic symptoms of allergy–itching, wheezing, vomiting, diarrhea–the body’s misguided and ultimately self-destructive attempt to purge itself of these foreign invaders. If unchecked (with a dose of Benadryl and/or epinephrine), the runaway reaction can lead to full-blown anaphylaxis and death.
Given this scenario, physicians reasoned that eliminating the most allergenic proteins from the diets of infants would give their immune systems a chance to develop, assuming that a mature immune system would be more likely to correctly recognize these foods as benign, reducing the chances of the body mounting an allergic response when the child is finally introduced to the proteins.”We knew that the human immune system is immature for the first year or so. So I was thinking initially that, as long as we don’t expose babies to a food, they can’t make an immune response,” Sampson explains in The New Yorker article. “And if we can wait until their immune system matures after a few years they could do better when later exposed to the food.”
In 1998, Groopman writes, that reasoning became the official policy of the Department of Health in the United Kingdom; two years later, it was adopted by the American Academy of Pediatrics. But not everybody agreed. Groopman’s champion emerges in the person of Dr. Gideon Lack, a pediatric allergist at St. Mary’s Hospital in London, who told Groopman, “If eating eggs or eating peanuts in an allergic sufferer causes a reaction, then clearly the way to prevent a reaction from occurring is by not eating egg or peanut. That makes sense. But that’s different from saying that clearly the way to not become allergic in the first place is not to eat egg or peanut.”
Groopman writes that Lack’s “aha!” moment came during a lecture in Tel Aviv in 2003, when he asked an auditorium packed with Israeli pediatric allergists for a show of hands if they had diagnosed a case of peanut allergy in the past year and perhaps three indicated that they had. “Lack told me that if he had asked that question in the United Kingdom, ninety to ninety-five per cent would have raised their hands,” Groopman writes. Teaming up with Israeli pediatricians, Lack conducted an epidemiological study of more than 5,000 students at Jewish schools in London and a similar sample of students at schools in Tel Aviv, comparing the diets of the children and incidence of food allergies in both cities. Lack found that childhood food allergy was exponentially higher in London than in Tel Aviv: peanut allergy, 11 times higher; tree nut allergy, 14 times higher; sesame allergy, five times higher; for milk and egg allergy, the risk factor was two to three times higher. Lack suspects a difference in diet is responsible for the disparity, particularly for peanut allergy, noting that Israeli children encounter the protein early in their lives, in the form of a peanut paste called ‘Bamba,’ a staple for Israeli infants. Even more intriguing, Groopman notes, are studies Lack conducted at the National Jewish Medical Research Center in Denver that showed laboratory mice could develop allergies to egg protein that was inhaled or rubbed on their skin, without ever actually consuming the substance, and another study, published in The New England Journal of Medicine in 2003, of nearly 14,000 American preschool children which concluded that the same mechanism seemed to be at work in humans: children with eczema who had been exposed to a skin ointment containing peanut oil later developed allergies to peanut protein. ”Doing nothing more than inhaling or touching an allergen could prompt a reaction in some children,” writes Groopman, who notes that Lack’s studies eventually persuaded other researchers, most notably, Hugh Sampson, to question the conventional wisdom of dietary restrictions and peanut allergy, which seemed to have made the problem even worse. “You can’t avoid food proteins,” Sampson tells Groopman. “So when we put out these recommendations we allowed the infants to get intermittent and low-dose exposure, especially on the skin, which actually may have made them even more sensitive.”
In 2008, the American Academy of Pediatrics reversed its food allergy feeding guidelines.
In a current study funded by the Food Allergy Initiative and Food Allergy & Anaphylaxis Network, Lack, is comparing the rates of peanut allergy in 640 infants randomly selected to eat peanut products or avoid them altogether, attempting to verify his hypothesis that children develop tolerance to a host of different food proteins by exposure to the proteins during the first six months of life.
The moral of this story? Parents of children with life-threatening food allergies might find some solace in what one allergist tells Groopman: “I try to emphasize with my patients not to feel guilty that they did or did not do something that would have resulted in their child having a food allergy. Even the experts are not certain what to advise.”