D: How was your workout this morning, Yaël?

Y: Great! I didn’t think I’d like going to the gym this early, but it actually feels pretty good.

D: I told you it’d be fun. Anyway, I’m going to go shower and brush my teeth, and then I’m off to work.

Y: You don’t use mouthwash after you brush your teeth, do you?

D: Sometimes. Why?

Y: It might not be a great idea right after working out, at least if you want to experience the blood pressure-reducing effects seen after exercise. Mouth bacteria play an important role in reducing blood pressure after we exercise, and using antibacterial mouthwash can get rid of it. Scientists did a study where they had 23 healthy adults run on a treadmill for a total of 30 minutes on two occasions, and then monitored them for the next two hours. At 1, 30, 60, and 90 minutes after running, the participants rinsed their mouth with a liquid—either antibacterial mouthwash or a mint-flavored placebo. Their arterial blood pressure was also measured. Researchers found that when the participants rinsed with mouthwash, the blood pressure-lowering effect of exercise was diminished by over 60% in the first hour after exercise and completely gone two hours after exercise compared to participants who rinsed with the placebo. That’s because the bacteria in our mouth synthesize a compound called nitrite. When we swallow nitrite in saliva, it gets absorbed into our bodies and widens our blood vessels even after we finish exercise, which keeps blood circulation high, and kick-starts a healthy blood pressure-lowering response called post-exercise hypotension.

D: Wow. I can still brush my teeth though, right?

Y: I’d recommend it.