When I was about 8, I wanted to marry a chicken farmer (it never occurred to me that I could simply be a chicken farmer, but that’s besides the point). My family now jokes that I am fulfilling that dream by studying Salmonella enterica, a bacterium best know for being found in, well, chickens…
At any rate, because my family generally kept our own flock of chickens, we rarely bought eggs from the store. I think I first started paying attention to egg labels in grad school, when I didn’t have the option of farm fresh eggs. At any rate, at some point I realized that there are a lot of labels on eggs and that most eggs do not come from chickens wandering around outside eating bugs and grass, like mine did.
In fact, most non-organic chickens in the U.S. are raised in one of three types of housing–cages, “cage free” also known as aviary-type housing, or enriched colony housing (1). The USDA considers caged laying operations the most common (2). A recent study by a group of academics and USDA scientists found that chickens in all three types of housing were similarly healthy and didn’t show signs of systemic stress in an autopsy (1). Surprisingly, mortality was actually highest for the cage-free (aviary) birds, in part due to increased number of pecking injuries (1). It’s important to note that in all three of these systems, the birds are raised indoors, in a climate controlled system (1). Many people consider the aviary-style cage-free housing to be the most humane of the indoor options (hence the advertisement of it on the egg carton), but these study results suggest that the chickens may not care particularly. Or perhaps the bigger differences would be found between birds with outdoor access and birds raised indoors, like the ones in this study. Hopefully the USDA will study this further at some point!
With that background out of the way, on to egg labels. The American Egg Board published the best summary I’ve seen of labels below (if you can’t read it, there’s a version you can zoom in on here). It is important to note that many of these are industry definitions, rather than USDA-recognized marketing claims. For instance, “cage free eggs” and “free range eggs” are not USDA-recognized labels (3). On the other end of the spectrum, “Certified Organic” means the producers must adhere to government standards (NOTE: “organic” has a much looser definition (3,4)). Much like with organic milk, organic eggs come from animals fed organic food, not given antibiotics, and given access to the outdoors (4).
This second chart is especially interesting, as it explains in detail some of the stamps you might see on an egg carton. I’d like to point out the comments on the GMO-free and antibiotic free labels. Yes, as the AEA delicately points out, they are meaningless labels; eggs are always GMO free, and are extremely unlikely to contain antibiotics. So, in the wonderful world of egg buying, it really is “let the buyer beware” of the labels. Don’t pay extra for meaningless labels, or feel warm and fuzzy because you grabbed the GMO-free dozen.
Finally, if you are worried about harmful bacteria, the study I mentioned earlier found that chickens from all three systems had similar (low) levels of Salmonella in their eggs (1). A study comparing eggs from caged chickens vs free range chickens also found similar levels of Salmonella or Campylobacter (another foodborne bacterium) in the eggs from the two systems (5). Another study found that free range hen’s eggs actually had a higher level of Salmonella and Campylobacter than caged hen’s eggs (6). So, at best, free range is no safer than conventional (while neither of these studies focused on organic eggs, it’s unlikely to be significantly different).
Ultimately, then, if organic or free range eggs aren’t necessarily from healthier chickens or providing better food safety, it’s a personal matter for the consumer.
Sources and additional information:
(1) Coalition for Sustainable Egg Supply (Researchers from Michigan State University, University of California, Davis, Iowa State University, and USDA Agricultural Research Service all participated in the research. Specialized ergonomics research was provided by Cargill Kitchen Solutions). (2010ish?) The Research Results Report: http://www2.sustainableeggcoalition.org/document_center/download/public/CSESResearchResultsReport.pdf
(2) USDA Egg Grading Manual. 2000. https://www.ams.usda.gov/publications/content/egg-grading-manual
(3) USDA Grademarked Product Label Submission Checklist. https://www.ams.usda.gov/sites/default/files/media/USDA%20Grademarked%20Product%20Label%20Submission%20Checklist.pdf
(4) National Organic Program: Organic Livestock and Poultry Practices. 2017. https://www.regulations.gov/document?D=AMS-NOP-15-0012-6680
(5) D. R. Jones ,*1 K. E. Anderson ,† and J. Y. Guard *. 2012. Prevalence of coliforms, Salmonella, Listeria, and Campylobacter associated with eggs and the environment of conventional cage and free-range egg production. Poultry Science. 91:1195-1202
(6) M.A. Parisi, J.K. Northcutt, D.P. Smith, E.L. Steinberg, P.L. Dawson. 2015. Microbiological contamination of shell eggs produced in conventional and free-range housing systems. Food Control. 47:161-165