If you’re a kid living in the city, you’re a lot more likely to have a food allergy than if you live out a farm. In fact, you’re also more likely to have a food allergy than kids living in your city’s suburbs or in adjacent small towns, with the gap growing as the population decreases.
A study published in the July 2012 issue of Clinical Pediatrics found that in cities, almost 9.8 percent of young people have food allergies, while only 6.2 percent of rural kids had this condition. Shellfish allergies were three times as common in city kids and peanut allergies were double the farm incidence.
Using data from a survey of 38,465 young people from infancy to age 18, “we have found for the first time that higher population density corresponds with a greater likelihood of food allergies in children,” says lead author Dr. Ruchi Gupta, an assistant professor of pediatrics at Northwestern University’s Feinberg School of Medicine and a physician at the Ann & Robert H. Lurie Children’s Hospital of Chicago. Previously, similar demographic trends have been found for the incidence of environmental allergies and asthma.
The study, funded by the Food Allergy Initiative (FAI), effectively “maps” the occurrence of food allergy across the United States. The states with the highest rates of food allergy (greater than 9.5 percent) were Florida, Georgia, Nevada, New Jersey, Delaware, Maryland and Alaska. Gupta is also the author of a 2011 study that found 8 percent of children across the United States have food allergies.
In an interview with Allergic Living, Gupta notes intriguing trends that need more investigation. For instance, she says she is fascinated to find a greater tendency to have food allergy in southern states – which she agrees is contrary to studies that find vitamin D in areas with stronger sun exposure may protect against allergies. She also sees proximity to water as a variable that deserves more scrutiny.
Q&A on Food Allergy’s Geographic Traits
Allergic Living Editor Gwen Smith interviews Dr. Ruchi Gupta about her new study that ‘maps’ food allergies across the United States.
Q. Your study is titled “Geographic Variability of Childhood Food Allergy in the United States”. In creating a U.S. map of this disease, what struck you the most?
Dr. Gupta: We didn’t just map urban vs. rural. We did urban centers vs. metro cities, then urban outskirts, suburban areas, small towns and then rural areas. When we started looking at food allergy prevalence by population density, it was amazing to me that it steadily decreased, it wasn’t like it went up and down and up and down. Urban centers had more food allergy than metro cities, which had more than urban outskirts, which had more than suburban areas, and so on. It went down in a very step-wise fashion.
What’s going on here is real: there is some relation between food allergy prevalence and population density. But that’s the million dollar next question: What is it? What’s going on in more populated areas to cause more food allergies?
[For a follow-up study] I think it would be ideal to follow kids who live in different environments and observe their lifestyles, and focus in on the cleanliness factor, or how much outdoor playtime they have and what the pollution is like in their area, and specifically, what are they eating in all these different areas, and where do they get that food from?
Q. I was intrigued by your finding of more food allergy in southern states. What could you tell us about that?
Dr. Gupta: Yes, we haven’t talked about it much, but it’s fascinating to me. I kept staring at the map we were creating and thinking: ‘What is going on? Is it states near water? Or is it southern?’
But with southern states vs. northern states, there’s the whole lack of vitamin D theory [as a cause of allergies]. I don’t want to take anything away from the vitamin D theory because I can’t say that we can prove or disprove simply based on this study. Yet, it’s interesting that, generally, southern areas of the U.S. and areas near water do have a higher prevalence of food allergies in this study.
Q. Among the states with the highest prevalence of food allergy, you’ve got Florida, Georgia, Alaska, New Jersey, Delaware, Maryland. Everything other than Nevada is near water.
Dr. Gupta: Yes and Nevada was high, 9.5 percent. One or two will throw you off, but I think in general you do see those two trends, even if they are not absolutely consistent.
We tried to look at whether there are more seafood allergies in these states. That wasn’t significant. But our numbers aren’t huge once we take the 40,000 in the study and put them all across the U.S. However, that would be interesting – is there any relationship between what people tend to eat in those areas and food allergies?
I was also interested in whether the types of foods kids are allergic to vary based on where they live. Peanut allergy was the highest in the urban, metro cities and suburban areas, but when you got out to rural, milk allergy was the highest.
So that does make me very curious as to: ‘Do the types of food allergies you have vary based on where you live and what you tend to eat?’
[The rate of] milk allergy was consistent, wherever you lived, but peanut did fluctuate from 2.8 percent in urban to 1.3 percent in rural. Then there was shellfish allergy – it was 2.4 percent in urban areas down to 0.8 percent in rural areas. That’s fascinating. And fish wasn’t even on the map for rural.
Q. Our readers will likely know of your studies, but they may not know that you have a daughter with food allergies. Has that influenced your interest in this work?
Dr. Gupta: Yes, I’m 100 percent passionate about it. I feel like food allergy is my world. It’s a daily life issue for me that doesn’t stop when I go home. I see how sad my daughter gets every time she picks up a food product and I have to take it away from her. She’s doing great and learning a new skillset, and she’s so responsible. But it can be very challenging for families, and for me personally.
Food Allergy Prevalence by Geographic Area |
|||||
|---|---|---|---|---|---|
| Urban Centers 9.8% |
Metro Cities 9.2% |
Urban Outskirts 7.8% |
Suburban Areas 7.6% |
Small Towns 7.2% |
Rural Areas 6.2% |
| Peanut 2.8% |
Peanut 2.4% |
Peanut 1.8% |
Peanut 2.0% |
Peanut 1.6% |
Milk 1.5% |
| Shellfish 2.4% |
Milk 1.8% |
Shellfish 1.5% |
Milk 1.5% |
Milk 1.4% |
Peanut 1.3% |
| Fin Fish 1.8% |
Shellfish 1.4% |
Milk 1.4% |
Shellfish 1.2% |
Wheat 1.1% |
Shellfish 0.8% |
| Milk 1.8% |
Tree nut 1.3% |
Tree nut 1.0% |
Tree nut 1.2% |
Shellfish 1.0% |
Tree nut 0.6% |
| Egg 1.3% |
Egg 1.0% |
Fin Fish 0.7% |
Wheat 0.8% |
Tree nut 0.9% |
Egg 0.5% |
Graph courtesy of Clinical Pediatrics, July 2012 edition
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