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Speaker 1: Welcome to brain Stuff from How Stuff Works High Brain

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Speaker 1: Stuff Lauren Vogel bomb Here, we often think of food

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Speaker 1: allergies as kids stuff. You know, a peanut free elementary

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Speaker 1: school classrooms, a special carton of dairy free ice cream

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Speaker 1: at birthday parties, and that one friend who couldn't eat

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Speaker 1: anything containing red food die, which meant you got all

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Speaker 1: their primo Halloween candy. But we don't always develop our

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Speaker 1: allergies as children. It's just that childhood food allergies are

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Speaker 1: studied more often than those acquired in adulthood. However, new

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Speaker 1: research presented at the annual meeting of the American College

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Speaker 1: of Allergy, Asthma and Immunology found that of all American

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Speaker 1: adults with food allergies have at least one allergy that

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Speaker 1: only materialized in adulthood. In the Chicago based research team

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Speaker 1: found that at least fifteen percent of adult food allergy

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Speaker 1: patients receiving care at Northwestern Medicine had at least one

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Speaker 1: adult onset food allergy. However, this was a small, non

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Speaker 1: representative sample of just Chicago area adults for this new study,

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Speaker 1: these of it a nationally representative sample of more than

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Speaker 1: fifty thousand adults, allowing the researchers to draw conclusions about

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Speaker 1: the national prevalence of adult onset food allergies, and it's

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Speaker 1: a lot higher than anyone anticipated given studies from previous decades.

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Speaker 1: The research team notes that while a two thousand four

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Speaker 1: study estimated that two point five percent of adult Americans

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Speaker 1: were allergic to shellfish, the most common food allergy among

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Speaker 1: adults in the United States, this twenty seventeen study found

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Speaker 1: that number is more like three point six percent of

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Speaker 1: the population. The same goes with tree nut allergies. A

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Speaker 1: two thousand eight study estimated that only zero point five

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Speaker 1: percent of American adults were allergic, but this new data

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Speaker 1: saw a two hundred and sixty percent increase, with an

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Speaker 1: estimated one point eight percent of adults having to avoid

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Speaker 1: everything from ntella to Reese's peanut buttercups. We spoke with

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Speaker 1: one of the studies co authors, Christopher Warren, whose a

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Speaker 1: doctoral candidate in preventative medicine at the University of Southern California,

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Speaker 1: via email. He said adult onset allergies are particularly interesting

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Speaker 1: to study because they likely involve losing immune tolerance to

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Speaker 1: foods that adults have already been previously exposed to and

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Speaker 1: eaten without having an allergic reaction. This is in contrast

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Speaker 1: to childhood food allergies, which involve the immune system failing

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Speaker 1: to develop tolerance to these allergic foods in the first place.

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Speaker 1: There may be two distinct mechanisms at work here. So

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Speaker 1: why would adults be losing their immunity chops when it

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Speaker 1: comes to certain foods. A possible clue might lie in

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Speaker 1: the demographic trends found in the study. The research team

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Speaker 1: found that certain populations were more at risk for specific

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Speaker 1: adult onset food allergies than others. For instance, Hispanic adults

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Speaker 1: were more than twice as likely to develop allergies to

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Speaker 1: peanuts than whites, and Asians were more than twice as

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Speaker 1: likely to develop shellfish allergies than whites. Warren said that

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Speaker 1: there are a number of hypotheses for why this may be.

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Speaker 1: For example, the cultural differences in the way that people

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Speaker 1: of different backgrounds prepare allergenic foods could possibly influence the

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Speaker 1: rates of allergies to those foods. According to Warren, when

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Speaker 1: foods like peanuts are roasted in the presence of sugar,

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Speaker 1: undergoing a browning process known as the Millard reaction, compounds

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Speaker 1: called advanced glycati and end products are created. These compounds

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Speaker 1: have been shown to increase the allergenicity of foods. Boiling foods,

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Speaker 1: on the other hand, tends to make their proteins less allergenic.

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Speaker 1: This hypothesis may explain the low rates of peanut allergy

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Speaker 1: in Asia, where peanuts are typically boiled or fried, relative

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Speaker 1: to the Americas, where peanuts are typically dry roasted. This

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Speaker 1: is consistent with what the current research team found out

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Speaker 1: about the prevalence of seafood allergies among Asian American participants.

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Speaker 1: Other population based studies conducted in Asia have found that

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Speaker 1: shellfish allergies are the most common allergy among older children

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Speaker 1: and adults there as well. However, diet might not have

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Speaker 1: everything to do with why certain populations develop allergies to

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Speaker 1: specific foods with higher frequency. Warren told us about an

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Speaker 1: ongoing study into the allergies of over five thousand children

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Speaker 1: that's being conducted in Australia called health Nuts. He said

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Speaker 1: a recent work out of the Health Nuts cohort in

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Speaker 1: Australia suggests that the Asian environment may be protective against

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Speaker 1: food allergy. Australian born Asian children are at a much

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Speaker 1: higher risk of developing food allergies than Asian born kids.

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Speaker 1: It's who moved to Australia, possibly because they've been exposed

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Speaker 1: to a different diet, bacterial, and uv environment. Warren and

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Speaker 1: his co authors are interested in looking at differences in

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Speaker 1: food allergy prevalence in the United States to see if

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Speaker 1: similar differences are observable among US immigrants relative to those

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Speaker 1: born in the States. We'll be on the lookout for updates.

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Speaker 1: Today's episode was written by Jesslyn Shields and produced by

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Speaker 1: Tristan McNeil. For more on this and lots of other

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Speaker 1: health topics, visit our home planet, how Stuff Works dot com.