It is important to recognize that the major food allergens, accounting for 90% of food allergy, are predominantly foods that are not genetically modified. The major food allergens are milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat, of which only soy is GM at this time (ibid.). The majority of food allergies and the vast majority of food allergies which tend to be most persistent after childhood (peanut, tree nut, seafood) involve NON-GM foods. To date, no reports exist of individuals who have developed sensitivity to proteins added via the genetic modification of foods, nor is there any evidence that genetic modification has increased the allergenic potential of foods. Studies of allergy-related (IgE) antibody binding using serum from food allergic individuals have not demonstrated consistent differences with GM vs. conventional food when examined (soybean). In short, there is no evidence that GM foods have contributed in any manner to changes in the prevalence of food allergy, nor is there a reasonable hypothesis suggesting that they would or could do so.
So, why the increase? Your inquiry is based upon a CDC Data Brief (2008, http://www.cdc.gov/nchs/data/databriefs/db10.htm). While there is evidence that food allergy prevalence in childhood is increasing in the US, a recent review by Chafen et al states that, for all ages combined, [w]hether the prevalence of food allergies is increasing is not well established (http://jama.jamanetwork.com/article.aspx?articleid=185820).
While hospital discharges for children under 18 with any diagnosis related to food allergy did indeed increase according to the CDC by 263% (1998-2000 vs. 2004-2006), increases in the rate of survey-reported food or digestive allergy in the preceding 12 months show a much more modest increase of 18% from 1997 to 2007 (same CDC report). It is thus clear that the hospital discharge diagnosis rate greatly overestimates acute food allergy prevalence.
Why might this be the case? The data cited refers to the number of hospital discharges with “any diagnosis” (as opposed to a primary diagnosis) of food allergy – meaning (in medical survey jargon) that the hospitalization did not necessarily occur BECAUSE of food allergy, but only that a food allergy diagnosis was included among the multiple diagnostic codes recorded at discharge. Diagnostic codes include those for allergic rhinitis due to food, allergic gastroenteritis and colitis, contact dermatitis due to food in contact with skin, dermatitis due to food taken internally, and anaphylactic shock due to food. As stated by the CDC, [t]his finding could be related to increased awareness, reporting, and use of specific medical diagnostic codes for food allergy or could represent a real increase in children who are experiencing food-allergic reactions. Diagnostic techniques, including endoscopic biopsy, controlled food challenge, etc. have also become increasingly available for use in children, and with an increasing interest in food allergy and intolerance, it is likely that elective hospitalization for diagnostic procedures related to food allergy diagnosis and treatment has increased.
To better understand these data, we downloaded the National Hospital Discharge Survey data (publicly available, see CDC report for links to data and documentation) to look for selected diagnostic codes covering food anaphylaxis (995.6) and non-infectious or allergic gastroenteritis and colitis (558.3 and 558.9) for the years 1996, 2000, 2007 and the latest year available, 2010. The number of discharges surveyed varies by year and is not directly available for all years, so total number of codes is used as a surrogate value (note that 2010 survey goal was reduced 50% due to budgetary constraints). The table shows actual values in parentheses and values adjusted to 1996 sample size to allow for more direct comparison.
Year Total codes (actual) adjusted (actual) adjusted
1996 278956 (22) 22 (3012) 3012
2000 310393 (21) 18.9 (2832) 2551
2007 362179 (32) 24.6 (3414) 2626
2010 150100 (14) 25.9 (1427) 2642
This is a crude analysis based on available data. We did not perform an analysis for statistical significance but would note that the rates of anaphylaxis have increased 17.7% from 1996 to 2010- essentially identical to the 18% increase in survey-reported anaphylaxis noted above- and that rates of non-infectious and allergic gastroenteritis and colitis have not increased. This would strongly indicate that the 263% increase in hospitalization rates cannot be explained by an increase in food related anaphylaxis or allergic enteritis.
While the reasons for increases in allergy rates are not known, and while a review of the subject is beyond the scope we can cover here, many allergists believe that this shift may be due to reductions in early infection and allergen exposure (the hygiene hypothesis) or may be due to delays in food introduction (recommended without proof of benefit and now perhaps proving to contribute to risk).
(NOTE: GMO soy was introduced in the US food supply in 1996, seventeen years ago.)