Vaping damages microbiome health in a strange way, new study reveals

About eight years ago, Deepak Saxena and his eight-year-old son walked down 3rd Avenue in Manhattan when they passed a banner advertising a sleek, relatively new product — electronic cigarettes, better known as vapes.

The boy looked up at his dad and asked, "Is smoking cool, Papa?"

Saxena, a molecular pathobiologist at the NYU College of Dentistry, tells IE it was in that moment while walking his son home from school that led him to start investigating the health effects of vaping.

Back in 2014, there was "no awareness, no regulation... no funding" for such research, Saxena says.

He got some seed money from NYU to get started. When the National Institutes of Health began allocating funds a couple of years later, Saxena's group was one of the four projects the NIH sponsored.

The group's most recent study — the first to track how vaping affects the bacteria in the mouth over time — was published this week in the academic journal mBio. Collectively, the community of microorganisms and different types of bacteria are known as the microbiome. 

"Our thinking was that the microbiome [of e-cigarette users] will be similar [either] to the combustible cigarette users or to the non-smokers," Saxena says.

Instead, researchers discovered that vaping has unique effects on the microbiome in the mouth. It's more than just a curiosity: Many species they found secrete molecules that provoke chronic immune responses that damage the body's cells. Essentially, the mouths of people who vape might be sabotaging the rest of the body in their unique way, but scientists are not sure at this early stage.

"The big issue with that is we don't know what that microbiome is going to do to health," Saxena says.

The oral microbiome responds to whatever goes into the mouth

Each segment of the digestive tract, from mouth to rectum, has a bacterial ecosystem uniquely suited to that particular "habit and environmental condition," Saxena says.

For example, the mix of bacteria that manage to live in the highly acidic stomach are different from the mix of bacteria that set up shop in the more-or-less neutral mouth.

As recently as ten years ago, researchers thought the mouth was home to maybe 20 or 30 types of bacteria. New tools that make it easier (and cheaper) to decipher DNA have shown that estimate was off by a factor of 100.

Collectively, our mouths are probably home to between 2,000 to 3,000 species of bacteria, Saxena says. A healthy, freshly brushed mouth might have between 100 and 200 species of bacteria present at any given time, at levels that can be detected.

Those bacteria are sensitive to their surroundings.

"If there is a trauma or... an ecological imbalance, the [levels of] good bacteria go down, and the [levels of] bad bacteria come up," he says. "Bad" bacteria are strains found in out-sized numbers in the mouths of people with problems like tooth decay or gingivitis.

Anything that goes into the mouth can change the environmental conditions and throw the microbiome off balance.

The ingredients in processed foods, for instance, feed species of bacteria that secrete acids. That isn't good for a couple of reasons. First, the acids strip minerals away from the surface of teeth. Even worse, those acid-secreting bacteria thrive in a more acidic environment while making life miserable for many kinds of bacteria that prefer the neutral pH of a healthy mouth. It's a downward spiral.

The new research suggests that vaping might cause similar feedback loops in the mouth.

Vaping is associated with nasty bacteria and dangerous proteins

In the new study, Saxena and his colleagues learned how the environmental changes caused by vaping affect the microbiome. They recruited 87 volunteers who either didn't smoke, smoked regular cigarettes, or vaped.

Each volunteer went into the lab twice, six months apart. Researchers inspected their mouths for clinical signs of problems like gum disease. They also took a lot of samples of the bacteria in their mouths and of molecules called cytokines, which are proteins involved in immune response and inflammation.

Everyone in the study had at least mild gum disease to start, in common with nearly half the adult population 30 or older. After the second visit, it was clear that people who vape tended to have a symptom of gum disease called "clinical attachment loss," which is the physical separation of the gum from the tooth.

The receding gums leave empty pockets where bacteria thrive, often leading to even worse gum disease. In this small study, the people who vaped experienced more clinical attachment loss than the smokers or the non-smokers in the study.

When it came to the participants' microbiomes, the researchers found a tremendous variation. The participants only shared about 20 percent of the same species of bacteria, with the people who vape having more in common with cigarette smokers than non-smokers.

"Vaping appears to be driving unique patterns in bacteria and influencing the growth of some bacteria in a manner akin to cigarette smoking," says Fangxi Xu, a co-author and member of Saxena's lab.

By the second visit, members of all three groups had more types of bacteria in their mouths, but the three microbiome profiles remained distinctive.

Finally, the researchers found different levels of cytokines across the three groups. People who vape, for instance, had much higher levels of a molecule called TNFα, which causes inflammation and has been linked to diseases including Alzheimer's, depression, and inflammatory bowel syndrome.

This small protein isn't necessarily a "bad" molecule; it's a critical part of necessary immune responses to real threats and is used to treat some cancers. It can create severe consequences if it's hanging around for a long time and causing chronic inflammation.

"Chronic inflammation... can also alter the microbiome," he says. That's what happens further down the digestive system in people with Crohn's disease.

"It's a vicious cycle. You have inflammation in the gut. You have it in the microbiome, you have a bad microbiome, you have more inflammation," Saxena says. 

The vape users also had lower levels of other cytokines associated with good oral health, including IL-4. Levels of that protein tend to go down when people have gum disease and then increase after treatment. That tells researchers that vaping somehow makes the mouth more inviting to bacteria that suppress immune responses.

These problems disproportionately affect young people. 

Vapes "were marketed to the public as something safe," Saxena says. Companies like Juul made it seem like electronic cigarettes "are the best product you can have" if you're going to smoke, he says.

The marketing worked. 

By 2020, roughly five percent of middle-school students in the U.S. used e-cigarettes, and approximately 20 percent of high school students did so, according to the F.D.A. According to a Gallup poll, one in five adults between 18 and 30 vape regularly. That's more than twice the number of adults in any other age group.

While the researchers found that vaping affects the body in a far more similar way to smoking than not smoking, young people don't see it that way. Roughly four out of five 18- to 30-year-olds say smoking is "very harmful to health," according to Gallup data. Just one in five thinks vaping is very harmful to health.

Saxena says there is far more to learn about how vaping — and the various components, including nicotine and flavoring agents — affect the body, including the microbiome. 

"We don't have any long-term data," he says.

It took researchers decades to understand the effects of smoking and convince policymakers to take action. Hopefully, it won't take quite as long for a clearer picture of vaping to come into view.  

Study Abstract:

Introduction: Tobacco use is one of the main causes of periodontitis. E-cigarette are gaining in popularity, and studies are needed to better understand the impact of e-cigarettes on oral health.

Objective: To perform a longitudinal study to evaluate the adverse effects of e-cigarettes on periodontal health.

Methods: Naïve E-cigarette users, cigarette smokers, and non-smokers were recruited using newspaper and social media. Age, gender, and ethnicity, were recorded. Participants were scheduled for two visits 6 months apart. At each visit, we collected data on the frequency and magnitude of e-cigarette and cigarette use, and alcohol consumption. Carbon monoxide (CO) levels, cotinine levels, salivary flow rate, periodontal probing depth (PD), bleeding on probing (BoP), and clinical attachment loss (CAL) were also determined at both baseline and follow-up visits and compared between groups with two-way repeated measures ANOVA. Periodontal diagnosis and other categorical variables were compared between groups with the chi-square statistic and logistic regression.

Results: We screened 159 subjects and recruited 119 subjects. One-hundred-one subjects (31 cigarette smokers, 32 e-cigarette smokers, and 38 non-smokers) completed every assessment in both visits. The retention and compliance rate of subjects was 84.9%. The use of social media and craigslist was significant in recruiting e-cigarette subjects. Ethnicity and race differed between groups, as did average age in the male subjects. Carbon monoxide and salivary cotinine levels were highest among cigarette smokers. Bleeding on probing and average PDs similarly increased over time in all three groups, but CAL uniquely increased in e-cigarette smokers. Rates of severe periodontal disease were higher in cigarette smokers and e-cigarette users than non-smokers, but interpretation is confounded by the older age of the cigarette smokers.

Conclusion: Among the recruited participants, CAL after 6 months was significantly worse only in the e-cigarette smokers. This study design and protocol will assist in future larger studies on e-cigarette and oral health.