Many consumers associate organic food production with food safety. While there is an abundance of persuasive arguments supporting this connection, the claims are often not accompanied by credible, scientific studies. As a result, it is unclear whether advocating for organic production methods will actually lead to a safer food supply.
For a study to be recognized by the scholarly community it must usually go through a process called peer review. This process subjects the author’s work to an impartial review by experts in the same field, who examine the methods, interpretations, and potential biases of the study.
One level above a peer-reviewed study is a meta-analysis. A meta-analysis is essentially a study of multiple peer-reviewed studies. The authors begin by surveying the literature, then select several quality studies relevant to the research question, and finally run statistical and analytical tests to derive their conclusions.
The objective of this article is to summarize the findings from two meta-analyses that compared the prevalence of various foodborne pathogens between organic and conventional farming methods. It should also be noted that while E. coli O157:H7 and Salmonella were addressed in both meta-analyses, there were inconsistent findings between the relatively few studies and neither was discussed in great depth. Additionally, the focus of this article is solely on meat and dairy products, so it is entirely possible that fruit and vegetable production might have different results.
Article 1: Meat
The first meta-analysis was a comparison of bacteria and antimicrobial resistance in organic and conventional poultry, swine, and beef (Young et al. 2009). The study included a total of thirty-eight articles (1991 to 2008) from around the world, selected based on relevance and quality (sample size, statistical method, etc.). While two statistical tests did not reveal any publication bias, it was also not completely ruled out. Additionally, most of the studies were observational cross-sectional studies, which can only provide evidence of association, not causation.
1. There appears to be no difference in the prevalence of Campylobacter in organic and conventional retail chicken. The study found a higher prevalence of Campylobacter in organic broiler chicken at slaughter, but there was no difference at the retail level. One proposed explanation for the difference at the slaughter level is that organic chickens come from a slower-growing breed. The study also found that consumption of organic meats was a significant risk factor for C. jejuni. This conclusion was based on only one study, and the authors noted that future case-control studies would be needed before organic meat could be considered a risk factor for this illness.
2. Bacterial isolates from conventional broiler chicken, turkey, and swine production exhibited more antimicrobial resistance and multi-drug resistance than isolates from organic production. The article also found that the prevalence of ciprofloxacin-resistant Campylobacter was higher in conventional compared to organic retail chicken. Ciprofloxacin is an antibiotic used to treat severe cases of Campylobacter infection, so an infection from conventional meat may not respond as well to the drug. Additionally, significantly higher multi-drug resistance was reported in bacterial isolates from conventional chicken, swine, and pork in comparison to organic meat products, which suggests that antimicrobial use practices on conventional farms are more selective of multi-drug resistance than those on organic farms.
Article 2: Dairy
The second meta-analysis compared bacteria, antimicrobial resistance, and somatic cell count in organic and conventional dairy production (Wilhelm et al. 2009). A total of 32 studies (1992 to 2004) from around the world were found to be of high enough quality to be analyzed, and another 15 descriptive studies were also reviewed. The authors noted that there was potential publication bias based on language restriction.
1. There does not appear to be an association between prevalence of bacteria, antimicrobial resistance, or somatic cell count and dairy production type. In general, no consistent association was observed between the prevalence of zoonotic bacteria and whether production was organic or conventional. The authors noted that many of the studies conducted in the US sampled essentially the same group of herds, suggesting that the outcomes were not independent of one another. The number of studies for each type of bacteria was also very limited.
2. Smaller herd size was associated with higher somatic cell count irrespective of production type in North America. Somatic cell count can be an indicator of infections, so a lower level is desirable. Among four studies that controlled for herd size, no difference in somatic cell count was found in two studies, another study found that the difference was attributable to age-specific stratum, and the last study found a significantly higher level of somatic cells on organic dairy farms.
There are many reasons why consumers choose organic foods. Some believe that organic foods are of higher nutritional value, others fear the potential effects of pesticides and genetic modification, and many decide based on environmental or ethical concerns. Reducing the risk of foodborne illness, however, is not as compelling. The only significant difference between organic and conventional meat products appears to be antimicrobial resistance and multi-drug resistance. This means that people are as likely to be sickened from either, but an illness from an organic source might allow them to respond better to medication. Additionally, there does not appear to be any significant difference between organic and conventional dairy products. In fact, given that organic dairy farms tend to have smaller herd sizes, organic milk might actually have a higher level of somatic cell counts than conventionally produced milk.
While foodborne illness is only one of several issues important to our food system, it should not be taken lightly. In the U.S., there are an estimated 2.4 million Campylobacter infections and 1.4 million cases of Salmonella each year (pdf). These infections result from consuming food from a wide variety of sources, both organic and conventional. As a result, it is important to remember that proper safety precautions should be observed with all types of foods, regardless of the production method.
Wilhelm B, Rajić A, Waddell L, Parker S, Harris J, Roberts KC, Kydd R, Greig J, Baynton A. Prevalence of zoonotic or potentially zoonotic bacteria, antimicrobial resistance, and somatic cell counts in organic dairy production: current knowledge and research gaps. Foodborne Pathogens and Disease. 2009;6(5):525-539.
Young I, Rajić A, Wilhelm BJ, Waddell L, Parker S, McEwen SA. Comparison of the prevalence of bacterial enteropathogens, potentially zoonotic bacteria and bacterial resistance to antimicrobials in organic and conventional poultry, swine and beef production: a systematic review and meta-analysis. Epidemiol Infect. 2009;137:1217-1232.© Food Safety News