Romantics say the eyes are the windows to the soul. Dentists say the mouth is a window into what's going on in the rest of your body.

That’s why the results of a new study from researchers at NYU College of Dentistry on the effects of vaping on oral health are a cause for concern. The results link vaping to oral infections and concerning changes to the mouth’s microbiome — a community of over 600 kinds of bacteria.

Previous research has shown that cigarette smoking disrupts the harmonious balance of microorganisms in your mouth. This new research reveals that e-cigarettes — often posited as the healthier alternative to smoking — also cause the mouth's microbiome harm.

What effect does an altered oral microbiome have on your overall health? If the delicate equilibrium of microbes in your mouth is tipped out of balance, it may change an e-cigarette user’s immune response, and users “may be left more vulnerable to other infections,” co-senior author Xin Li, associate professor at NYU College of Dentistry, tells Inverse.

This research was published Wednesday in iScience.

Vaping and the oral microbiome

The researchers examined the oral microbiome of 119 subjects, including people who regularly use e-cigarettes, cigarette smokers, and people who had never smoked before. They found that, while the rate of gum disease or infection was still overwhelmingly the highest amongst cigarette smokers (72.5 percent), those who used e-cigarettes still had experienced significantly higher rates than those who didn’t use e-cigarettes or traditional cigarettes — 42.5 percent in e-cigarette users as opposed to only 28.2 percent non-smokers.

Vapers were found to have an abundance of the bacteria P. gingivalis. Shutterstock

When the researchers looked at the saliva of their subjects, they discovered that the microbiome of e-cigarette users differed significantly from that of the other two cohorts. Using a technique to profile microbial communities known as 16S rRNA high throughput sequencing, e-cigarette users were found to have an abundance of the bacteria P. gingivalis, which is known to trigger gum disease.

They also found that those who used e-cigarettes had elevated levels of the cytokines interleukin-6 and interleukin- 1β, which are substances that induce inflammation. This may have the overall effect of making users more prone to inflammation and infection. The researchers also exposed cells to e-cigarette aerosols and found that the exposure made the cells more susceptible to the development of infection.

Why a healthy mouth matters

In recent decades, oral health has been linked to many systemic diseases, Li explains. For example, gum disease has been linked to diabetes, heart disease, and Alzheimer’s disease.

Deepak Saxena, a professor at NYU College of Dentistry and another co-senior author on the paper, says the effects that vaping has on the mouth may be mirrored in the rest of the body. Because e-cigarette use seems to have an inflammatory effect in the mouth, “it could be causing inflammation in the respiratory tract also,” he tells Inverse.

The use of e-cigarettes, or vaping, is experiencing a massive boom as of late. Their popularity is especially prevalent amongst teenagers: More than 5 million U.S. middle and high school students are current e-cigarette users. The Food and Drug Administration (FDA) described e-cigarette use as a “crisis among America’s youth.”

However, as they are so new, scientists are still learning about their health consequences, particularly in the long-term, and it is increasingly coming to light that they may prove far more dangerous than previously thought.

This new work is but another addition to the list of potential negative health effects of vaping, and, although still better than smoking, the effects of e-cigarette use on oral health should not be brushed aside.

Abstract: The trend of e-cigarette use among teens is ever increasing. Here we show the dysbiotic oral microbial ecology in e-cigarette users influencing the local host immune environment compared with non-smoker controls and cigarette smokers. Using 16S rRNA high-throughput sequencing, we evaluated 119 human participants, 40 in each of the three cohorts, and found significantly altered beta-diversity in e-cigarette users (p = 0.006) when compared with never smokers or tobacco cigarette smokers. The abundance of Porphyromonas and Veillonella (p = 0.008) was higher among vapers. Interleukin (IL)-6 and IL-1b were highly elevated in e-cigarette users when compared with non-users. Epithelial cell-exposed e-cigarette aerosols were more susceptible for infection. In vitro infection model of premalignant Leuk-1 and malignant cell lines exposed to e-cigarette aerosol and challenged by Porphyromonas gingivalis and Fusobacterium nucleatum resulted in elevated inflammatory response. Our findings for the first time demonstrate that e-cigarette users are more prone to infection.