The interactions of diet, mood, and the gut microbiome during an eight-week submarine deployment

ABSTRACT Disruption of the gut microbiome has been linked to ill health, including impaired cognitive performance and mental health issues. Various aspects of a prolonged submarine deployment environment are known to disrupt the microbiome when they occur in other circumstances, including limited diet, altered circadian rhythm, poor sleep, and stress. In this study, we (i) characterize the changes of diet, mood, and the composition of the gut microbiome during a prolonged submarine deployment and (ii) determine whether any of these factors interact and affect submariner health and performance. Thirty-four U.S. Navy submariners, serving on a ballistic missile submarine (SSBN), provided fecal and blood samples and completed questionnaires relating to their diet and mood. Samples and questionnaires were collected at six time periods covering before, during, and after an 8-week deployment. Fecal samples were analyzed by 16S rRNA gene sequencing. Blood samples were analyzed to identify biomarkers with established links to stress, neurocognitive function, immune function, and gut barrier function. The dietary and mood questionnaires were analyzed to identify any changes over the course of the deployment. Results indicated that baseline gut microbial diversity was highly variable between individuals, although certain microbes had deployment-related changes to their composition. Changes in microbiota composition within individuals over the course of the deployment were correlated with changes in diet and mood, suggesting a link between microbiome composition and feelings of fatigue. Identification of microbial communities that confer resiliency to deployment stressors will enable future development of targeted interventions. IMPORTANCE Submariners operate in a unique deployment environment, but their experiences may shed light on how the human body responds to extended duration missions in other confined spaces, such as spaceflight. Our study is the first to show how the human gut microbiome changes during an extended submarine deployment while also tracking dietary intake and mood.