So, why would adults be losing their immunity chops when it comes to certain foods? A possible clue might lie in the demographic trends found in this study. The research team found certain populations were more at risk for specific adult-onset food allergies than others. For instance, Hispanic adults were all more than twice as likely to develop allergies to peanuts than whites, while Asians were more than twice as likely to develop shellfish allergies than whites.
"There are a number of interesting hypotheses currently under investigation as to why this might be," says Warren. "For example, the intercultural differences in the ways that allergenic foods are prepared could be influencing the rates of food allergy to those foods."
According to Warren, when foods like peanuts are roasted in the presence of sugar (undergoing a browning process known as the Maillard reaction), compounds called advanced glycation end products (AGEs) are created. AGEs have been shown to increase the allergenicity of foods. Boiling foods, on the other hand, tends to make their proteins less allergenic. This hypothesis may explain the low rates of peanut allergy in Asia, where peanuts are typically boiled or fried, relative to the Americas, where peanuts are typically dry roasted. This is consistent with what the research team found out about the prevalence of seafood allergies among Asian-American participants: Other population-based studies conducted in Asia have found shellfish allergies are the most common allergy among older children and adults there as well.
However, diet might not have everything to do with why certain populations develop allergies to specific foods with higher frequency.
"Recent work out of the HealthNuts cohort in Australia suggests that the Asian environment may be protective against food allergy," says Warren. "Australian-born Asian children are at much higher risk of developing food allergies than Asian-born kids who move to Australia, possibly because they have been exposed to a different diet, bacterial and UV environment."
Warren and his co-authors are interested in looking at differences in food allergy prevalence in the U.S. to see if similar differences are observable among U.S. migrants relative to those born in the States.