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United States Department of Agriculture

Agricultural Research Service

Title: The Hygiene Hypothesis and Food-Borne Illnesses: Too Much of a Good Thing? Or Is Our Food Supply Too Clean?

Authors
item Callaway, Todd
item Harvey, Roger
item Nisbet, David

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 28, 2006
Publication Date: September 1, 2006
Citation: Callaway, T.R., Harvey, R.B., Nisbet, D.J. 2006. The hygiene hypothesis and food-borne illnesses: Too much of a good thing, or is our food supply too clean? Foodborne Pathogens and Disease. 3:217-219.

Interpretive Summary: This is the first in a series of challenge or "devils advocacy" articles in Foodborne Pathogens and Disease designed to bring issues to the attention of the scientific community for further discussion and routes for potential future research. The food supply in the United States, Canada and Europe is one of the safest in the history of the world. Yet the consequences of food-borne illnesses have increased proportionally with the rise in immunosuppressed and elderly populations in these nations. We have done a great job at reducing bacterial loads on foods, and the resultant increase in food safety and shelf life have enhanced productivity and efficiency. However, the hygiene hypothesis suggests that as we have cleaned up our environment, including the food supply, we may have become more susceptible to other illnesses. Reduced exposure to dirt and commensal bacteria has resulted in a doubling in allergies in the U.S., and this is theorized to be due to a lack of activity of the immune system. Consequently, autoimmune disease diagnoses have risen dramatically as well. Exposure to commensal organisms on food can provide a microbial population to the gut, and to provide non-specific immunity against some pathogens. Reducing this exposure means that the gut microbial diversity is lessened, and the immune response mounted by the host to a true pathogen invasion is dampened. Foods presented to human consumers contain few bacteria to challenge the immune system and provide non-specific immunity. This may clear the way for further auto-immune type illnesses or providing a threat-free environment for pathogen colonization. By providing nearly sterile foods, we may be creating a paradox by invoking the law of unintended consequences and reducing our innate and acquired resistance to food-borne illnesses.

Technical Abstract: This is the first in a series of challenge or "devils advocacy" articles in Foodborne Pathogens and Disease designed to bring issues to the attention of the scientific community for further discussion and routes for potential future research. The hygiene hypothesis states that as our environment has become cleaner, the risks of illnesses (including food-borne illness) have paradoxically increased. In this monograph, we discuss the concept of the hygiene hypothesis and how it is applied to food safety. Exposure to commensal organisms on food can provide a microbial population to the gut, and to provide non-specific immunity against some pathogens. Reducing this exposure means that the gastrointestinal microbial diversity is lessened, and the immune response mounted by the human to a true pathogenic infection is dampened. This may allow pathogens an opportunity to colonize and proliferate in the gut before a response can be generated. In this era of increasing elderly and immunocompromised populations providing nearly sterile foods, may be invoking the law of unintended consequences and reducing our innate and acquired resistance to food-borne illnesses.

Last Modified: 9/2/2014
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