Food Allergies: Nature or Nurture?

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The emerging field of epigenetics has added a new dimension to the “nature versus nurture” debate, by which researchers have historically attempted to determine whether a characteristic was influenced by genes or environment. Increasingly, it appears that environmental influences can affect gene expression, meaning that “nature” and “nurture” are inextricable from one another to an even greater extent than previously understood.

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A recent article published in Clinical and Experimental Allergy notes that epigenetic factors can help explain the significant increase in food allergy prevalence in developed nations [1]. The mechanism by which the rate of food allergy has increased so rapidly has been puzzling to researchers; it’s happened too quickly to be accounted for purely in genetic terms. However, food allergies appear to have a strong genetic component, since they run in families and co-occur with a number of other related disorders, including eczema and asthma. In fact, it appears that there are two influences that increase the likelihood of an individual having a food allergy: genetic predisposition (family members with allergies), and a “modern lifestyle” [2].

How does the environment influence genetics? Simply put, an individual’s characteristics are encoded in genetic material — DNA — but not everything encoded in DNA is actually expressed.

Some genes remain “silent,” and researchers are increasingly realizing that environmental factors may cause the expression of genes that, in the absence of that environmental trigger, would have remained inactive. In a very real sense, the environment can turn genes on and off, changing physical characteristics, influencing health, and affecting behavior. Furthermore, it seems that the prenatal period — the time during which a fetus is developing in utero — is particularly important with regard to epigenetic influences [3].

While the scientific understanding of food allergies (and of epigenetics in general) is still in its infancy, it appears that researchers will increasingly focus on the effects of environmental triggers on gene sequences that predispose individuals to develop allergies. In so doing, it might someday be possible for those individuals from families with high risk of allergies to avoid the environmental triggers that turn allergy-related genes on in the first place.

References

1. Tan et al. The role of genetics and environment in the rise of childhood food allergy. Clin Exp Allergy. 2012 Jan;42(1):20-9. doi: 10.1111/j.1365-2222.2011.03823.x. Epub 2011 Jul 19.
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2. Jackson, M. Allergy: the making of a modern plague. Clin Exp Allergy. 2001 Nov;31(11):1665-71.
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3. Bird, A. Perceptions of epigenetics. Nature. 2007 May 24;447(7143):396-8.
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