Post-exercise hypotension and skeletal muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria.
Level 2 - randomized trial
Randomized, double-blind, crossover trial in humans
PubMed 31369841 · doi:10.1016/j.freeradbiomed.2019.07.035
What was done
In a randomized, double-blind, crossover study, 23 healthy participants (15 males, 8 females) completed two moderate-intensity treadmill exercise sessions. Following exercise, participants rinsed with either an antibacterial mouthwash to inhibit oral bacteria or a placebo mouthwash. Systolic blood pressure (SBP) was measured before exercise, and at 1 hour and 2 hours post-exercise. Blood and salivary samples were collected before and 2 hours post-exercise to quantify nitrate, nitrite, and the oral microbiome. Microvascular reactivity was assessed via a reactive hyperemia test evaluating tissue oxygenation index (TOI).
What was found
In the placebo condition, exercise significantly reduced SBP at 1 hour (-5.2 ± 1.0 mmHg; P < 0.001) and 2 hours (-3.8 ± 1.1 mmHg; P = 0.005) compared to baseline. This was accompanied by a significant rise in circulating nitrite at 2 hours (100 ± 13 nM vs. baseline 59 ± 9 nM; P = 0.013) and an increase in peak TOI during hyperemia (86.1 ± 0.6% vs. baseline 84.8 ± 0.5%; P = 0.010). With antibacterial mouthwash, the SBP-lowering effect was attenuated by 61% at 1 hour and completely abolished at 2 hours. The antibacterial condition also prevented the post-exercise rise in circulating nitrite (P > 0.05) and the increase in peak TOI (84.6 ± 3.2% vs. baseline 85.1 ± 3.1%; P > 0.05). Oral bacterial diversity was unaffected by either treatment.
Why it matters
This study demonstrates that oral commensal bacteria and their nitrate-reducing activity are necessary to trigger post-exercise hypotension and enhanced muscle oxygenation in healthy adults.
Limits
The study had a small sample size (n = 23) restricted to healthy individuals, meaning results cannot be directly generalized to hypertensive populations. Long-term cardiovascular impacts were not evaluated beyond a 2-hour recovery window, and diastolic blood pressure outcomes were not reported in the abstract.
Cited by
- supports Using antiseptic mouthwash immediately after a workout negates the blood pressure-lowering effects of exercise.