making the connection between nutrition & health

Is Our Environment and Lifestyle Causing Allergies?

This is a thought provoking question that is being asked in light of the epidemic of allergies in the United States.  Perhaps one of the best ways to address it is to compare allergy rates in children born outside the U.S. to that of those born and residing in the U.S.

Research presented at the American Academy of Allergy, Asthma and Immunology suggests that the answer is a strong “yes”.  The data from the 2007-2008 National Survey of Child Health compared the rates of several forms of allergic disease in children between 0-17 years of age who were born and resided in the United States to that of children born in other countries but who had more recently moved here.  The data is very convincing.  All forms of allergic disease were much lower in those who were born elsewhere but recently relocated to the United States.

 

 

 

 

 

 

 

 

 

A second piece of data was even more convincing of the relationship.  Those children who were born outside the United States and moved here developed allergy rates 3 to 6 times higher after 10 years of U.S. residence.  This takes the issue of genetic background out of the equation and clearly makes the issue the U.S. environment.

This data strongly supported previous studies which found higher rates of allergic disease in highly developed nations.  This higher rate has been attributed to the “hygiene hypothesis” which suggests that the excessive use of antibiotics and other similar practices during childhood in highly developed nations is a predominant factor.  Children receiving repeated antibiotic exposure during the first year of life have been shown to have a doubling of allergy rates.  The hypothesis suggests that tolerance in the immune system must be trained in children with a reasonable amount of challenge by microorganisms.

Other factors explaining this epidemic have evolved.  It seems that allergies are rare in parts of the world where minor parasite infections are high.  Children previously infected by helminth parasites were found to have very low allergy rates.  It seems that the parasitic infection “teaches” the immune system self tolerance.  The lesson is not that children should be allowed to get these minor parasite infections but more what these infections do.  They lead to the development of an immune cell called CD4+ Treg cells which are important in learning immune self tolerance.  Allergies are simply a self immune attack.

It seems that the friendly bacteria that live in the human digestive tract also lead to the development of an immune cell called CD4+ Treg cells.  Unfortunately, these bacteria are reduced by therapeutic antibiotic exposure, so hence the allergy connection to antibiotic use. 

Most of these bacteria are transferred from the mother to the infant during birth and during breast feeding.  If the mother’s “population” had been altered by antibiotic use or antibiotic pass-through from standard meat/dairy/eggs, the child’s “population” is then affected.  Early probiotic use has been shown to decrease the risk of allergic disease by age 2 by 60%

Another piece of the puzzle is our food environment.  The immune system must react to everything foreign and decide to activate or tolerate.  Many of the foreign substances in food in the U.S. are not allowed in many other developed nations, and packaged, manufactured food does not exist in under-developed nations.  Dyes are a perfect example.  A recent uproar over a different version of macaroni and cheese with artificial dye being sold in the U.S. than the version sold in Europe where these dyes are banned is telling.

Allergies are in many ways just an angry immune system that decides to attack “self”.  As we understand what makes the immune system excessively angry, preventing and correcting the problem seems realistic.

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