Food

As with water, food is essential for survival, and its availability, preservation, and preparation are all important considerations for public health practitioners. Historically, food shortages, often the result of climatic changes, have apparently been a major factor in both epidemics of infectious diseases and in social unrest and armed conflict (McMichael, 2012). Famine has also resulted in large scale human migrations, such as in the Irish Potato Famine of the 19^th century.

Although famine and food shortages continue to be a significant concern in parts of the developing world – contributing to the civil war and unrest in Somalia and to high rates of farmer suicides in India in recent years – there has been growing concern in the US over the issues of both rising levels of obesity and “food deserts”, which are defined as “area[s]…with limited access to affordable and nutritious food, particularly such an area composed of predominantly lower income neighborhoods and communities” (CDC).

The two issues are thought to be at least partly related, as lack of access to supermarkets or farmers’ markets generally means limited availability of affordable fresh produce and other healthy foods. Additionally, there has been considerable controversy regarding the role of heavy marketing of snack foods, beverages and fast foods in a shift away from a healthier, more balanced diet. Although this focus has, to an extent, triggered some increased media interest in homegrown foods and home canning, this also raises concerns about proper preservation of foods in order to prevent growth of contaminants such as Clostridium botulinum, the etiologic agent of botulism, or other bacterial pathogens.

As a veterinarian, much of my public health training has centered on maintaining and ensuring the safety of animal-based foods. Salmonella serovars are often associated with infected poultry products, including eggs; E.coli, especially the O157:H7 strain, have been associated with numerous cases of contaminated beef; and Listeria monocytogenes has been an important pathogen in outbreaks involving processed meats. And although the rate of foodborne illness hasn’t increased significantly in the past 30 years, these organisms continue to be of significant importance. The economic costs of these and other foodborne diseases are estimated at $10 to $83 billion per year in the US alone (Nyachuba, 2010).

One of the factors in the development of large foodborne illness outbreaks in the US has been the dominance of large-scale factory farming. Although it has allowed for overall greater efficiencies in food production, it has also enabled contamination to occur on a larger scale with much wider distribution. This is not to suggest that the problem is unidimensional, however.

In the case of swine production, for example, while conventional factory farming has been associated with widespread presence of multi-drug resistant strains of Salmonella (Gebreyes, et al., 2000), a study comparing the conventional factory-farmed pigs to outdoor-raised, antibiotic-free pigs found the outdoor-farmed pigs had higher levels of seropositivity to Salmonella, Toxoplasma, and even Trichinella, which had largely been eradicated as a public health concern in the US (Gebreyes, et al., 2008).

In a global economy, tracing the origin of contaminated foods can sometimes be a great challenge with significant economic ramifications. In the 2011 outbreak of E. coli O104:H4 in Germany and France, for instance, cucumbers from Spain were initially implicated as the likely source, resulting in considerable market upheaval. Ultimately, however, molecular epidemiologists determined that the source of infection was seed sprouts that had been shipped to a German distributor from Egypt in 2009. That distributor supplied seeds to the sprout farm found to be the point source of the outbreak in Germany, as well as to a British company which repackaged the seeds and sold some in France, which were the source of a smaller outbreak there. (Grad, et al. 2012)

With regard to plant-based foods, a concern that garners a good bit of media attention is that of pesticide residues on fresh fruits and vegetables, with a growing push from consumers for locally produced and organic foods. A newly published review of available data, however, indicates that imported fruits and vegetables actually tend to have lower prevalence of pesticide residues than conventional domestically-grown produce. Additionally, organically-grown produce is not necessarily free of residues, though residue prevalence and levels are generally much lower. That said, the residues present in conventional domestic produce were still generally measured at levels below those established by the EPA for chronic exposure (Winter, 2012).

The development of improved technologies to identify contaminants, though, promises to be an important area of focus to address the issue of global movement of foods. Had the above European outbreak occurred 20 years earlier, the source could have been much more challenging to identify and the outbreak much more widespread. Tools currently in development, such as an electronic “nose” to detect traces of toxins or pathogens before they enter the human food chain, may also go a long way to improving food safety. (Eifler, et al. 2011)

References

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

McMichael, A.J. “Insights from past millennia into climatic impacts on human health and survival”. Proceedings of the National Academy of Sciences. 2012 Feb 6. doi: 10.1073/pnas.1120177109.

Centers for Disease Control and Prevention. Healthier Food Retail: Beginning the Assessment Process in Your State or Community. http://www.cdc.gov/obesity/downloads/HFRassessment.pdf

Nyachuba, D.G. “Foodborne illness: is it on the rise?”. Nutrition Reviews. 2010 May; 68(5):257-269. doi: 10.1111/j.1753-4887.2010.00286.x

Gebreyes, W.A., et al. “Antimicrobial resistance of Salmonella isolates from swine”. Journal of Clinical Microbiology. 2000 Dec; 38(12): 4633-4636.

Gebreyes, W.A., et al. “Seroprevalence of Trichinella, Toxoplasma, and Salmonella in antimicrobial-free and conventional swine production systems”. Foodborne Pathogens and Disease. 2008 Apr; 5(2):199-203. doi: 10.1089/fpd.2007.0071.

Grad, Y.H., et al. “Genomic epidemiology of the Escherichia coli O104:H4 outbreaks in Europe, 2011”. Proceedings of the National Academy of Sciences. 2012 Feb 21; 109(8): 3065-3070. doi: 10.1073/pnas.1121491109.

Winter, C.K. “Pesticide residues in imported, organic, and suspect fruits and vegetables”. Journal of Agricultural and Food Chemistry. ePub 2012 Feb 15. doi: 10.1021/jf205131q.

Eifler, J., et al. “Differential detection of potentially hazardous Fusarium species in wheat grains by an electronic nose”. PLoS One . 2011 Jun; 6(6): e21026. doi: 10.1371/journal.pone.0021026.