Did you know that every day, we eat billions of microbes (bacteria, fungi, viruses) inhabiting our food? According to Wasserman et al. (2019), a single apple harbors about 100,000,000 bacteria, not to mention an unquantified number of fungi, viruses, and other microorganisms. Although food processors and manufacturers are careful to test for known pathogens, those comprise only a minuscule percentage of all the microbial life out there. And, since food testing is typically performed in the processing plant, not at the dinner table, we don’t really know which microbes live on and in the different types of food at the time we are eating them.
Garden-fresh foods have been subjected to less washing and sanitizing than supermarket produce and, thus, may still harbor indigenous plant- and soil- associated microbiota at the point of consumption. A recent study by Brown et al. (2022) found that during peak harvesting season, families that garden regularly and consume a substantial portion of their diet directly from their gardens tended to have more soil-associated bacteria in their feces than non-gardening families. Rather than being cause for alarm, these exposures are thought to be generally benevolent with regard to human health. For the vast majority of human evolution, exposure to soil- and plant-associated microbiota has been unavoidable and, in fact, may be important for maintaining health (Rook 2021). Supporting this theory, emerging evidence suggests that exposure to diverse microorganisms, such as those associated with traditional farm environments, can help train the immune system and reduce inflammation (Stein et al. 2016). In comparison, supermarket produce undergoes extensive handling and processing throughout its lengthy supply chain, and each instance of handling by human workers or contact with processing surfaces and liquids may alter the intrinsic microbiome of fresh fruits and vegetables. Dramatic changes in microbial composition from harvest to point of sale have been documented for supermarket produce. In some cases, fewer than 2% of the original microbial taxa remained at the point of sale; however, this was not a reduction in overall abundance of microbes but rather a shift from indigenous communities to other microbes acquired from the processing environment (Rosberg et al. 2021).
To better understand differences between the microbial communities of garden-fresh and store-bought fruits and vegetables, as well as their potential to influence the human gut microbiome, we are conducting a USDA-funded pilot study engaging 20 gardeners between the ages of 18–45 from the Willamette Valley (Oregon). This study involves two dietary intervention periods and self-collection of produce and fecal samples. We will be recruiting until October 15, 2023. If you are interested in learning more, check out the FAQ or go directly to the screening survey to see if you are eligible.