According to recent research, the use of antibacterial mouthwash inhibits the production of nitric oxide during exercise. This limits the vasodilating and blood pressure-lowering effect.
NO Boosters
NO (Nitric Oxide) Boosters are popular substances that are supposed to increase the production of nitric oxide. Nitric oxide causes blood vessels to dilate/widen. This has several positive effects on health in general and for athletes in particular. When blood vessels widen, blood pressure is lowered. Think of it as the same amount of water flowing through a garden hose with a larger diameter. In addition to the positive effect of lower blood pressure itself, this has several other positive properties. Think of waste products being more easily removed and nutrients being more easily delivered to muscle cells. We have also referred to studies showing that muscle cells can burn more sugars and fats as a result. Substances like arginine, citrulline, GPLC, are called NO boosters because they increase the production of nitric oxide. But even exercise itself acts as a NO Booster. Research from the University of Plymouth now shows that this nitrogen-increasing effect can be limited when using antibacterial mouthwash [1].Mouthwash and nitric oxide?
I must admit that I read the news with some surprise. “How do you even come up with investigating a connection between (antibacterial) mouthwash and nitric oxide?” This apparently was due to my limited understanding of the (re)production of nitric oxide. However, it also turns out that this lack of understanding may be forgiven. Only recently has the role of bacteria in the mouth in the production of nitrogen dioxide been understood.“Scientists already know that blood vessels open up during exercise, as the production of nitric oxide increases the diameter of the blood vessels (known as vasodilation), increasing blood flow circulation to active muscles. What has remained a mystery is how blood circulation remains higher after exercise, in turn triggering a blood-pressure lowering response known as post-exercise hypotension.” Dr Raul Bescos, University of Plymouth
Production of nitric oxide during and after exercise
Researchers previously did not understand why blood pressure remained lowered after exercise. Previous research suggested that this was not due to nitric oxide. Nitric oxide was thought to have this effect only during exercise. But in recent years, more has been understood about the production, or better said, reproduction, of nitric oxide. Dr Raul Bescos explains:“Nitric oxide breaks down into nitrate, which according to earlier beliefs would have no function in the body. Research over the past ten years, however, has shown that nitrate can be taken up by the salivary glands and leave the body through saliva in the mouth. Some bacteria in the mouth can take up nitrate and convert it into nitrite, an important molecule that can increase the production of nitric oxide. When nitrite is swallowed, part of this molecule is quickly absorbed into the (ed. blood) circulation and returned in the form of nitric oxide. This helps keep the blood vessels open longer and thus lowers blood pressure for a longer period.”
Antibacterial mouthwash and nitrate conversion
The researchers at Plymouth wanted to know if blocking the possible conversion of nitrate into nitrite would have an effect on lower blood pressure after exercise. They did this by inhibiting the bacteria in the mouth. They had 23 healthy adults run on a treadmill for half an hour at two different times. They were then monitored for two hours afterwards. In both situations, the researchers asked the participants to rinse their mouths after 30, 60, and 90 minutes; once with antibacterial mouthwash (0.2% chlorhexidine) and the other time with mint-flavored water. The researchers took blood pressure measurements and samples of blood and saliva before the exercise and two hours after the exercise.Effect of exercise on blood pressure reduced by more than 60%
Participants who rinsed with mint water saw their systolic blood pressure (upper pressure) decrease by an average of 5.2 mmHg one hour after running. However, participants who rinsed with antibacterial mouthwash saw this decrease by only 2.0 mmHg. This shows that the blood pressure-lowering effect of exercise (one hour after exercise) was reduced by more than 60% by the antibacterial mouthwash. Two hours after exercise, this effect was completely nullified. Previous research assumed that the main source of nitrite in the bloodstream was formed by nitric oxide produced in the cells in the walls of blood vessels (endothelial cells). This is challenged by this new research, which mainly points to the bacteria in the mouth as an important source for this molecule. At least for the first few hours after exercise. Co-author of the study, Graig Cutler, also points to existing studies showing that the use of antibacterial mouthwash at rest can increase blood pressure.Listerine in the trash?
It is good to point out that not all types of mouthwash need to have such an effect on nitric oxide and thus blood pressure. In this study, a mouthwash containing 0.2% chlorhexidine was used. Not for nothing; it is considered the most effective disinfecting mouthwash and therefore the most successful in killing bacteria [2]. The well-known Listerine does not contain chlorhexidine. A study from 1990 compared, among other things, the effect of chlorhexidine and Listerine on plaque formation and their ability to kill bacteria [3]. Chlorhexidine turned out to be the best, bacteria killer, while Listerine did not have this effect at all. According to another study from 1990, however, Listerine was found to kill the most bacteria in the mouth within 30 seconds [4]. Research from 2015 looked at the effect over a longer period of time, namely two weeks. Both Listerine and chlorhexidine were found to have a lowering effect on the amount of mouth bacteria, although chlorhexidine was once again the ‘winner’.Reference:
- C. Cutler, M. Kiernan, J.R. Willis, L. Gallardo-Alfaro, P. Casas-Agustench, D. White, M. Hickson, T. Gabaldon, R. Bescos. Post-exercise hypotension and skeletal muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria. Free Radical Biology and Medicine, 2019; 143: 252
- Amoian B, Omidbakhsh M, Khafri S. The clinical evaluation of Vi-one chlorhexidine mouthwash on plaque-induced gingivitis: A double-blind randomized clinical trial. Electron Physician. 2017;9(9):5223–5228. Published 2017 Sep 25. doi:10.19082/5223
- Efficacy of Listerine, Meridol and chlorhexidine mouthrinses on plaque, gingivitis and plaque bacteria vitality. Brecx M, Netuschil L, Reichert B, Schreil G. J Clin Periodontol. 1990 May;17(5):292-7.PMID: 2355095
- Kato T, Iijima H, Ishihara K, Kaneko T, Hirai K, Naito Y, Okuda K.Antibacterial effects of Listerine on oral bacteria. Bull Tokyo Dent Coll. 1990. Nov;31(4):301-7. PubMed PMID: 2133450.
- https://www.sciencedirect.com/science/article/abs/pii/S0891584919307610
