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.

Key Findings

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.

Key Findings

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.

Conclusion

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.

References

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.

Trans fats are generally considered unhealthy, and have long been linked to heart disease and obesity. These fats are created through a process called “partial hydrogenation,” where hydrogen is pumped into liquid oil at high temperatures. This process improves the shelf-life of foods, but the resulting trans fats have been shown to lower high-density lipoproteins (HDLs), the “good” cholesterol, and increase low-density lipoproteins (LDLs), the “bad” cholesterol. This in turn causes arteries to become more clogged and increases the risk for heart disease. One study even showed that just a 2 percent increase in energy intake from trans fats was associated with a 23 percent increase in the incidence of coronary artery disease (Mozaffarian et al. 2006).

For those involved in the movement against trans fats, California’s ban represents a huge victory for public health and serves as a model for other states to follow. Groups such as the California Academy of Family Physicians and the American Heart Association have rallied behind the state’s new law, and have urged other states to follow suit.

Not all organizations, however, have been as supportive of the ban. For example, the California Restaurant Association has argued that singling out trans fats is arbitrary and will prove costly to enforce. It also suggested that the ban should be handled on a federal level, not by individual states.

While some might question the restaurant association’s resistance to California’s ban, it does raise a valid concern: why is there a state ban on just trans fats?  Clearly, there is persuasive scientific evidence that trans fats are hazardous to public health.  Further, few would even try to argue that there is any appreciable benefit to the use of trans fats. Regardless, here are three reasons why banning trans fats may not be as important of a state health priority as many have suggested.

1. A product that does not contain trans fats is not necessarily healthy. When a restaurant stops using trans fats it likely uses saturated fats instead. Though saturated fats are not as harmful, there is still plenty of literature linking saturated fats to obesity and heart disease. But I am more concerned when businesses promote the health value of a product simply because it does not contain trans fats. To some customers, the absence of trans fats leads them to believe that it is safe to eat more. The next time you are in your grocery store, walk down the snack food aisle and count how many brands of chips advertise in large letters that they do not use trans fats. But look at the nutrition label and you will find that they still use plenty of saturated fats.

2. Similar restrictions could be made on just about any “bad” ingredient. For example, the government could put limitations on sodium content. Excessive sodium is known to raise blood pressure, which leads to hypertension, and there is also evidence that sodium adversely affects calcium and bone metabolism and even contributes to stomach cancer (Wardener and MacGregor 2002). While sodium in the diet is not necessarily unhealthy in lower levels (in contrast to trans fats), these days most people far exceed the recommended value because of processed and prepared foods. So why not limit the amount of salt that restaurants can use and require that all prepackaged foods meet the definition of “low sodium”? The ugly truth is – many people like the taste of salt. As a result, states are reluctant to place regulations on unhealthy foods because people value our right to choose – even if that means choosing unhealthy foods.

3. It can be a distraction from other health concerns. Presumably, the burden of enforcing a trans fat ban falls on health inspectors.  Personally, I would prefer that inspectors focus on looking for unsanitary cooking and storage conditions, rather than checking to see whether a restaurant is using margarine or butter. While consuming trans fats certainly contributes to heart disease, E. coli O157:H7 or Salmonella will make me sick right now. And based on the sheer number of foodborne illness outbreaks that have occurred just this year, my guess is that food inspection agencies are probably stretched quite thin already.

To clarify, I am not at all against banning trans fats.  In fact, a strong argument can be made to prohibit their use on a national level.  I merely question whether states should be handling this issue.  Not only will there be wasted resources due to 50 different legislative agendas, but the inevitable inconsistencies will likely lead to less industry compliance.  Federal law, on the other hand, will be easier for national restaurant chains and food manufacturers to comply with, and will also carry the full weight of federal agencies.  But then again, trans fats are only one problem in the food system, and there are plenty of other issues to tackle first.

References

Mozaffarian D, Katan M, Ascherio A, Stampfer MJ, Willett WC. Trans Fatty Acids and Cardiovascular Disease. N Engl J Med. 2006;354(15):1601-1613.

Wardener HE, MacGregor GA. Harmful effects of dietary salt in addition to hypertension. J Hum Hypertens. 2002;16:213-223.