Using mouthwash after exercising could negatively impact the cardiovascular benefits of working out, particularly lowering blood pressure, a new study claims.

The findings, published in Free Radical Biology and Medicine and led by researchers at the University of Plymouth in England, detail how using mouthwash after working out can prevent your body from reaching — and staying — in a low blood pressure range for a period of time post-exercise. Exercise has long been known to reduce blood pressure, though how exactly blood pressure levels stay low for hours after exercise has been a source of much debate.

For the study, which focused on the role of oral bacteria in reducing blood pressure following exercise, 23 healthy adults were asked to run on the treadmill for two 30 minute sessions. After working out, participants were monitored for two hours.

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During that time, they were asked to take periodic swigs of an antibacterial mouthwash or a mouthwash-resembling placebo.

By the end, researchers found those who used the mouthwash had higher blood pressure rates than those who used the placebo.

“These results show that the blood pressure-lowering effect of exercise was diminished by more than 60 percent over the first hour of recovery, and totally abolished two hours after exercise when participants were given the antibacterial mouthwash,” said a news release from the University of Plymouth regarding the findings.

One of the reasons for this, the researchers hypothesized, is the mouthwash’s effects on oral bacteria.

“Previous views also suggested that the main source of nitrite in the circulation after exercise was nitric oxide formed during exercise in the endothelial cells (cells that line the blood vessels)," researchers explained. "However, the new study challenges this. When antibacterial mouthwash was given to the participants, their blood nitrite levels did not increase after exercise. It was only when participants used the placebo that nitrite levels in blood raised, indicating that oral bacteria are a key source of this molecule in the circulation at least over the first period of recovery after exercise.”

Nitric oxide, according to Healthline, “is produced by nearly every type of cell in the human body and one of the most important molecules for blood vessel health.”

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Nitric oxide “relaxes the inner muscles of your blood vessels, causing the vessels to widen,” said Healthline. "In this way, nitric oxide increases blood flow and lowers blood pressure.”

Craig Cutler, a study co-author, explained that the findings show how important oral bacteria are to opening the body’s blood vessels.

“These findings show that nitrite synthesis by oral bacteria is hugely important in kick-starting how our bodies react to exercise over the first period of recovery, promoting lower blood pressure and greater muscle oxygenation,” he said. “In effect, it’s like oral bacteria are the ‘key’ to opening up the blood vessels. If they are removed, nitrite can’t be produced and the vessels remain in their current state."