Masticatory performance and fecal propionate levels in healthy young adults: a cross-sectional study

Masticatory function may influence the gut microbial metabolism via mechanical and neurohumoral mechanisms. However, the relationship between microbial metabolites and systemic indicators in healthy adults remains unclear.

This cross-sectional study included 20 healthy young adults (mean age: 27.6 ± 2.5 years). Masticatory performance was assessed using a validated chewing examination with gummy jelly as the test food. Fecal short-chain fatty acids were quantified by gas chromatography. Microbial metabolic functions were inferred using PICRUSt2 based on 16S rRNA gene sequences. Defecation frequency and body mass index were assessed using questionnaires and anthropometry, respectively. Correlation, regression, and mediation analyses were performed using 2,000 bootstrap samples.

Masticatory performance showed nominal positive associations with several microbial metabolic pathways (p < 0.05), but none remained significant after false discovery rate correction (q ≥ 0.05). Propionate concentration and masticatory performance showed trends toward associations with defecation frequency, although these associations did not reach statistical significance. The mediation pathway involving propionate and defecation frequency was suggested but not significant.

Overall, masticatory performance was associated with fecal propionate levels in healthy young adults. Associations among defecation frequency, BMI, and predicted microbial metabolic pathways are exploratory and require confirmation in larger studies.