Relationship between coffee concentration and bowel motility using bowel-sound-based stimulus-response plots in healthy individuals

Coffee is consumed worldwide and exerts multifaceted physiological effects, yet evidence on its short-term impact on intestinal motility remains inconsistent. We investigated 40-min changes in motility after coffee prepared at three concentrations (weak, strong, extra strong) in 10 healthy young men using bowel-sound–based stimulus–response plots (BSSRPs) derived from BS segments per minute. Concentrations were created by precisely adjusting instant-coffee powder per 150 mL serving at 45 °C to control total dissolved solids. Motility increased versus baseline in both post-ingestion phases (Gastric 0–10 min; Intestinal 20–40 min). Planned pairwise comparisons did not detect differences among concentrations within phase, whereas exploratory BSSRPs suggested a concentration-ordered inverse pattern (WC ≥ SC ≥ Ex.SC) that persisted across 0–40 min. These findings indicate that coffee acutely modulates intestinal motility under fixed temperature/volume conditions, while any concentration dependence remains provisional. This work provides a basis for more systematic evaluation of coffee’s physiological effects; future studies should standardize composition, temperature, and volume, include a matched hot-water control, and be powered to test concentration effects and mechanisms directly.