Lactic acid bacteria naturally associated with ready-to-eat rocket salad can survive during the human gastrointestinal transit
It was theorized that modernization and the decline in harmless microbial populations associated with food have altered the gut microbiota, impacting host metabolism and immunity. Western dietary patterns, characterized by processed foods and preservation methods, may play a significant role in reducing the microbial population associated with food. Integrating these diets with fermented foods, rich in lactic acid bacteria (LAB), is proposed to mitigate the consequences of bacterial deprivation. Nonetheless, non-fermented food consumed raw may also be an important source of viable microbial cells for the human microbiome. This study wants to investigate whether salad-associated LAB can survive the gastrointestinal transit (GIT) and contribute to the gut microbiota. LAB strains were quantified and isolated from rocket salad, and their survival through GIT was assessed via intervention trials in healthy adults and in vitro. Moreover, bacterial communities in fecal samples after three days of rocket salad consumption were analyzed. Washing with a sodium hypochlorite solution drastically reduced total bacterial load and eliminated viable LAB. The quantity of LAB introduced through salads did not significantly alter the gut microbiota composition. Rocket salads harbored Weissella and Leuconostoc species, with a higher LAB content associated with increased abundance in feces. Simulated GIT experiments suggested that food may have a protective role on bacterial viability. These findings propose that plant goods could serve as sources of live LABs for the human gut. Further research with diverse vegetables and longer interventions is needed, encouraging studies on raw, non-fermented foods and their impact on the human intestinal microbiome.