Researchers at the University of Minnesota found a positive relationship between the number of farmers markets per capita in a given state and the number of reported incidences of certain food-borne illnesses in that state.
The authors are careful to point out that it would be a mistake to interpret the results as saying that the foods purchased at farmers markets are somehow worse (i.e., more likely to make consumers ill) than the foods purchased at grocery stores because of the results. This is especially important given that even if what they have identified is a causal relationship rather than a correlation, the results do not allow studying the precise causal mechanisms through which farmers markets may increase the number of cases and outbreaks of food-borne illness. Indeed, most food safety problems come from the mishandling of foods by consumers or by restaurant staff who prepare those foods for consumers. As such, it is easy to imagine cases where consumers are more or less neglectful with foods purchased from farmers markets (e.g., by being less likely to wash produce from the farmers market, or by cooking eggs from the farmers market more thoroughly than eggs from the grocery store), which could explain the results. In other words, although the presence of farmers markets in a given state might well lead to more cases and outbreaks of food-borne illness, this research cannot pinpoint the precise causal mechanisms through which this occurs.
The researchers thus note that from a policy perspective, it would be a mistake to take the results in their paper and discourage or encourage people to purchase food from farmers markets on the basis of their results. The authors point out that even if their estimated relationships between farmers markets and food-borne illness were causal beyond all reasonable doubt, they cannot determine the precise mechanisms through which those relationships operate. This suggests further research for those interested in studying the relationship between farmers markets and food-borne illness should go—that is, the mechanisms whereby farmers markets might cause food-borne illness.
My thoughts are (and the authors point this out in another part of their paper) that farmers markets often sell foods from producers who are subject to a less stringent set of regulations than the foods sold at convenience stores, grocery stores, super markets, and big-box stores.
The typically remotely produced and procured foods sold at such stores are produced in the context of agricultural value chains by large, often multinational firms who face serious scrutiny from food-safety authorities. As a result, those firms have serious incentives to apply the strictest possible protocols.
I think the combination of less stringent standards for the producers of food that goes to farmers markets, along with the lack of care by consumers in washing such food, is the most likely reason for the results of this study.
It seems that the best solution is to get to know the producers at your local farmers market and to learn about their food-handling procedures. Once you find a producer who seems to take such an issue seriously, then the consumer needs to take some responsibility and wash the food thoroughly before eating it.
While such an approach does not guarantee that you will avoid all food-borne illnesses, I think it will decrease the likelihood of such an event.
As always, buyer beware.