Compared to the human gut microbiota, the oral microbiota remains relatively unexplored. However, emerging evidence suggests that it too plays a role in systemic health and may represent an untapped biomarker or therapeutic target for health and disease. Previous studies have shown that routine intensive exercise for more than 8 weeks can change composition of the stool microbiome. We aimed to evaluate oral microbiota amplicon sequence variant (ASV) level changes in a healthy cohort undergoing 11 weeks of intensive training and identify factors driving microbiota changes.
Participants (n=188, baseline) were healthy adults aged 18-36 years (88% male). Sampling and data collection was conducted at week 1, 5 and 11 of training. Saliva samples were collected using the passive drool method and sequenced by amplification of the V3-V4 hypervariable region of the 16S rRNA gene. Bioinformatics analysis was conducted in QIIME2. Data collection included various clinically validated questionnaires to evaluate self-reported mental and physical wellbeing, and a food frequency questionnaire to assess diet over the preceding 6 months, food diaries to assess current dietary macronutrient intakes, and baseline demographics. Blood samples were taken to quantify inflammatory markers. To achieve sufficient statistical power when assessing associations with covariates, data from all time points was combined and controlled for repeated measures design.
The oral microbiota at ASV level was highly variable over the study period, with a small but significant decrease in alpha diversity and a significant shift in beta diversity. None of the covariates assessed were associated with alpha diversity, but there were significant associations between beta diversity and past intake of dairy and meat, inflammatory cytokine TNF-α, and several elements of wellbeing (including emotional limitations, passion/perseverance, and stress). Time was the covariate with the most significant association with beta diversity.
Our study revealed significant longitudinal fluctuations in the oral microbiota of individuals undergoing intensive training, including aspects of wellbeing. Whilst further investigation using shotgun metagenomic sequencing for species and strain-level taxonomic annotation is needed to elucidate the health impacts of these associations, these results suggest that the oral microbiota may represent a potential non-invasive biomarker of wellbeing and inflammation.