Recent years have seen an explosion in novel food products in international and, especially, in U.S. markets. Many novel food products seek to address consumer concerns regarding environmental impact and nutritional quality of mass-produced foods. Others look to a growing population of consumers seeking alternatives to meat products. Although no single definition of “novel food” exists, we usually consider a food to be novel if does not have a significant history of human consumption. Examples include not previously consumed plant species, algae, insects, lab-grown (cultured) foods, and fungi. We may also consider a food to be novel to a region or country, meaning that a history of consumption elsewhere may exist. An existing food that undergoes radically different processing may also be thought of as novel.
The introduction of new species to the food supply raises the possibility of new food allergens. The prevalence of food allergy in the U.S. is approximately 3 to 4 percent, though estimates vary. A common misapprehension is that only certain foods cause allergic reactions. Allergy to some foods is thought to be more prevalent, more severe, or more difficult to avoid, and these are often required to be labeled by law (e.g., wheat, milk, egg, soy, fish, crustacean shellfish, tree nuts, and peanut in the U.S.). However, almost any food can be allergenic, and predicting allergenicity of a new food has proven to be a problematic safety and regulatory issue for the novel food industry.
The Molecules that Cause Food Allergy
Almost all food allergens are proteins. All living things contain protein, meaning all foods (unless extensively processed to remove protein) also contain protein. Many novel foods on, or entering, the marketplace are designed to replace existing protein-rich foods (particularly meat) and are, therefore, rich in protein themselves. Proteins are extremely varied in structure and function, a property that enables them to perform many different roles in the human metabolism. This variability also affects allergenicity, with only some proteins having significant potential to be allergens.
The Food Allergy Research and Resource Program (FARRP) AllergenOnline database currently contains 2,129 proteins that are known or suspected allergens, including those from food, airway allergen sources (pollen and fungi), contact (latex), and venoms. Newly identified allergens are added every year. However, despite a relatively large number of known allergens, we still don’t know precisely which properties of a protein cause them to be allergens. We do, however, have some clues that help us identify types of food that may be particularly problematic.
Sensitization, Elicitation, and Cross-Reactive Allergens
Most food allergens are thought to be capable of both sensitizing (“priming” the immune system to respond later) and eliciting (causing a reaction in a “primed” or allergic individual). There are many examples of individuals who are sensitized to one allergen who then react to similar proteins in different foods. This phenomenon is known as cross-reactivity. Banana/latex allergy and birch-pollen/fruit allergy are relatively well-known examples of this. That cross-reactive allergic reactions may occur due to the consumption of a novel food by an individual who’s already allergic to a known allergen is very much a possibility. In fact, the likely susceptibility of shellfish allergic consumers to reactions resulting from the consumption of insect-based foods is already known. However, we know that different allergic individuals react to allergens in different ways, and allergens that cross-react in one may not in another.
Allergic reactions to food occur when a specific type of antibody, IgE (immunoglobulin-E) binds to food allergens. The IgE molecules that allergic individuals possess vary greatly, even among those who react to the same protein in the same food. These different IgE antibodies recognize allergens differently. Cross-reactivity can, therefore, be very different even among individuals with similar food allergy diagnoses. Because of the occurrence of cross-reactive allergy, and because the sensitization stage of food allergy is currently very poorly understood, we mostly consider elicitation when examining the possibility of food allergy from novel foods.
Predicting Allergenicity of Novel Foods
There’s no diagnostic test to determine whether a food is an allergen. When researchers refer to allergenic foods, we rely on the experience of having foods in the marketplace over years or decades and observing patterns of allergy in a population. For novel foods this often isn’t possible, as by definition there’s no well-recorded history of consumption. Additionally, animal models of food allergy are poor and do not provide accurate predictions of responses in humans.