Karen Sweazea, PhD

Good ol’ mouthwash: Sure, it makes your breath minty fresh, especially after eating garlic bread with extra garlic. But did you know that using it could also raise your blood pressure? Surprisingly, it’s all related to nitric oxide.

Nitric oxide is a naturally occurring chemical in the body involved in the process of widening the blood vessels (among other functions). Your blood vessels increase in diameter in response to nitric oxide, as shown in the figure below. When blood vessels increase in diameter (dilate), blood pressure goes down. When they decrease in diameter (constrict), blood pressure goes up.

Credit: Elizabeth2424/Wikimedia Commons

As it turns out, some of the bacteria found in your mouth are also important in maintaining normal blood pressure because they help to make nitrite from foods rich in nitrates, such as beets, celery, lettuce and spinach. Nitrites are important because they can be changed to nitric oxide in the body. Research published in Free Radical Biology & Medicine shows that anti-bacterial mouthwash use increases blood pressure in healthy people after only one day of use because it decreases nitrite production in the mouth.

While this is a surprising finding, it’s probably not necessary to stop using mouthwash altogether. But it might be a good reason to add more nitrate-rich foods to your diet! Always be sure to speak with your doctor if you are concerned about your blood pressure and before making any changes that might affect it.

Karen Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.