Social media videos are claiming that mouthwash can raise risk of blood pressure - and potentially damage heart health.
According to some of these videos, this is caused by mouthwash wiping out "good" oral bacteria that are important for the cardiovascular system . While it's a striking message , don't throw your mouthwash away just yet. The reality is far more complex.
Our mouths contain a wide variety of bacteria. Together, these bacteria form a balanced and diverse microbiome which helps prevent the overgrowth of other bacteria linked to disease, supports normal metabolic functions and contributes to both good oral and overall health.
One of the important roles these oral bacteria have is converting the nitrate in our food (typically from sources such as leafy greens) into nitrite. When we swallow nitrite, the body turns it into nitric oxide. This happens via the nitrate-nitrite-nitric oxide pathway , also called the enterosalivary pathway. It's one example of how bacteria contribute to keeping the body healthy.
Nitric oxide plays an essential part in regulating blood pressure and supporting brain function and muscle function .
But according to some online influencers , the reason mouthwash harms heart health is because it affects the "healthy" bacteria - the ones that produce nitric oxide.
Mouthwash and heart health link
Several small studies have actually found that giving people mouthwash can change the balance of bacteria in the mouth. This may reduce the bacteria's ability to turn nitrate from vegetables into nitrite, which the body needs to make nitric oxide.
One study of 19 healthy volunteers found that the adults who used chlorhexidine mouthwash for seven days saw a small increase in blood pressure and reduced levels of nitrite.
An intervention study also reported that rinsing with 0.12% chlorhexidine gluconate mouthwash twice daily for one week significantly increased blood pressure in 27 healthy adults.
In another trial of 15 adults who already had high blood pressure, three days of chlorhexidine use further increased blood pressure.
The key detail that may be missed out of some of these online social media videos is the type of mouthwash used in these studies.
Many of the studies which have found a link between mouthwash use and blood pressure gave participants chlorhexidine. This is a strong, over-the-counter antiseptic mouthwash only recommended for short-term use in people with gum disease or after dental procedures where its antimicrobial effects are beneficial.
Chlorhexidine disrupts oral bacteria to help with infection control - including the bacteria that convert nitrate into nitrite. This makes it an ideal mouthwash to use for researchers wanting to study the nitrate-nitrite-nitric oxide pathway. However, it also means the findings may not reflect what happens with milder, everyday mouthwashes.
A trial with 12 healthy adults investigated the effect of three different mouthwashes (and gargling water, which acted as a control) on oral bacteria.
After drinking a nitrate-rich juice, researchers measured how much nitrate was converted to nitrite by oral bacteria. Water and the mild mouthwash (which didn't contain harsh ingredients such as chlorhexidine) caused a typical response, where nitrate was converted into nitrite.
But the cetylpyridinium chloride mouthwash (which also has strong, anti-bacterial effects) partially blocked the conversion of nitrate to nitrite. The strongest chlorhexidine mouthwash almost completely stopped this process. This is consistent with their stronger antibacterial effects. The stronger types of mouthwash were also linked to higher systolic blood pressure.
Alcohol (ethanol) is another common ingredient in many mouthwashes, although formulations usually also include other active ingredients - such as essential oils. This makes it difficult to isolate the specific effects of alcohol.
As an antimicrobial, alcohol may influence the oral microbiome. Some studies have even suggested a possible association between mouthwashes containing alcohol and increased oral cancer risk. However, there are currently no studies that have specifically examined the effects of ethanol-only mouth rinses on the oral microbiome or cardiovascular health.
Overall, the body of evidence suggests that a mild, over-the-counter mouthwash, like the kind most people buy at stores, may be less likely to significantly interfere with nitrate-to-nitrite conversion or affect blood pressure.
In a long-term study of 354 adults, better routine oral hygiene, such as brushing and flossing, was linked to a lower risk of cardiovascular death over nearly 19 years. Regular mouthwash use did not appear to have any influence on heart health outcomes. This was true for milder mouthwashes containing flouride and alcohol, as well as stronger, anti-bacterial mouthwashes such as chlorhexidine and cetylpyridinium chloride.
The type of mouthwash matters
Together, these studies suggest that some types of mouthwash (such as chlorhexidine) disrupt beneficial oral bacteria and the nitrate-nitrite-nitric oxide pathway when used long term. But more research needs to be done to truly understand the long-term effects of other types of mouthwash on cardiovascular health - including mild everyday mouthwash brands and those containing alcohol.
Mouthwash comes in different types for different purposes, so it's important to check the active ingredient on the back of the packaging. Alcohol-free and milder mouthwashes appear to have less effect on the heart-healthy bacteria than stronger types.
However, be aware to check the ingredients as even alcohol-free options can contain antibacterial agents such as cetylpyridinium chloride. As such, it's best to choose one that fits your needs and use it in moderation. Strong mouthwashes containing chlorhexidine are best reserved for helping gum disease or oral infections.
It's also worth noting that oral health and untreated infections can also contribute to heart disease more broadly. For example, a systematic review of 82 studies concluded that chronic oral disease and tooth loss was associated with risk of heart problems. This is why maintaining a healthy balance of mouth bacteria matters beyond your teeth.
Take care of your oral and overall health by keeping up with brushing, flossing, visiting your dentist and choosing a mouthwash that works for you.
Joanna L'Heureux does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
