Thursday, January 5, 2012

Food Allergy Theory

My PB&J yesterday
Why weren't kids allergic to peanut butter back in the 1950s and 60s?  My theory has always been that assaults on our immune systems by toxic chemicals in our environment are to blame.  It was revealed last year, for instance, that pregnant mothers living close to major traffic routes give birth to children with more medical problems, ostensibly due to air pollutants from vehicles.  Last week a new scientific study was published that hints at a behavioural answer, at least for allergies.  By Tom Blackwell of The National Post:  "People from well-educated families are almost twice as likely to suffer from some dangerous food allergies as others - possibly because their bodies’ natural defences have been lowered by rigorous hygiene and infection control, suggests a new Canadian study. The research from McGill University also found that immigrants were about half as likely to be afflicted by the allergies, perhaps reflecting differences in diet and environment between their countries of origin and Canada. The study was published in the Journal of Allergy. The link to higher education may be explained by what is called the hygiene hypothesis, the unproven idea that smaller families, cleaner homes, more use of antibiotics to treat infections and vaccines to prevent them have curbed development of the immune system, said Dr. Moshe Ben-Shoshan, who led the research. That in turn could make some people more susceptible to allergy. If the hypothesis does actually explain some food reactions, though, parents may not be able to do much about it, admitted the allergist at Montreal Children’s Hospital. The benefits of such health products as antibiotics and vaccines easily outweigh the risk of children developing serious allergies, said Dr. Ben-Shoshan. “On the flip side, worrying about every time the kid is exposed to another kid, washing them down in Purelle, that may not be the best thing.” The new study’s authors offer up other theories, too, for why the highly educated are more likely to develop food allergies. Better-schooled families, for instance, may be more apt to have heeded expert advice in the past that they delay giving children foods - like peanuts - that commonly cause acute allergies. That recommendation from allergy specialists has since been abandoned, amid newer evidence that suggests delaying introduction of those substances may actually make children more susceptible to food allergy, said Dr. Ben-Shoshan. It is also possible that some of those higher-educated families were simply more apt to seek medical help and get their children diagnosed for food allergies, the paper noted. The new study found that people in homes where the respondent had graduated from a post-secondary institution were almost twice as likely to have tree nut allergies, 63% more at risk of a peanut allergy and 2.4 times more apt to suffer from a sesame allergy. Immigrants were about half as likely as the average to suffer from any of the food allergies, the study suggested. That finding gibes with some other studies, including one that indicated the prevalence of asthma among Chinese teenagers was lowest in those from mainland China, greater in residents of Hong Kong and highest in ethnic Chinese born in Canada. It all suggests that food allergies might be partly related to environmental and diet factors, like the fact North Americans tend to eat more processed food and less fruit and vegetables."