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Heavy drinking may increase 'bad' bacteria in your mouth, study finds

Nights of hard drinking can lead to much more than just bad hangovers. In fact, new research suggests that heavy drinkers may actually experience higher levels of "bad" bacteria in their mouths, including bugs linked to gum disease, heart disease and cancer compared to moderate or non-drinkers.

» RELATED: Alcohol can damage DNA and increase risk of cancer, study shows

The study, published last week, examined the microbiome – the microorganisms inside the body – of 1,044 American adults who self-identified their drinking habits as non-drinkers, moderate drinkers or heavy drinkers. Drinking habits were defined based on the recommendations of U.S. health officials, who classify heavy drinking as one alcoholic beverage per day for women, or two for men.

Researchers looked at mouthwash samples from the participants, about 25 percent of whom identified as non-drinkers, 59 percent as moderate drinkers and 15 percent as heavy drinkers. When compared to the non-drinkers, drinkers – especially heavy drinkers – had fewer Lactobacillales, a type of "good" bacteria used commonly in probiotic supplements. The drinkers also generally had higher levels of "bad" bacteria, such as Actinomyces bacteroidales and Neisseria.

» RELATED: Just one drink a day can increase your risk of cancer, study says

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"We wanted to look at the question, 'What are the lifestyle factors that influence the oral microbiome?'" senior researcher Jiyoung Ahn of NYU Langone Health in New York City told CBS News.

"This is the first study to show this relationship, and more research is necessary," she said. "We already know that heavy drinking is a risk factor for many diseases. So, the possible effect on the oral microbiome is one more reason to avoid heavy drinking."

Emory University Winship Cancer Institute professor Nabil F. Saba, who was not involved in the research, told the AJC that the results are "certainly intriguing."

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"It is possible that these links could be the clue of understanding the process by which alcohol exerts its carcinogenic effect. Of course more research is needed to elucidate such an association," Saba said. "It is research that deserves attention and deserves further investigation,” but noted that "liver damage and resulting hepatocellular carcinoma – cancer of the liver – is one of the most serious possible consequences of excessive alcohol consumption.”

He suggested that follow-up research should look for associations between the oral microbiome and oral tongue cancer.

Other experts also pointed out that it's unclear whether the higher levels of bacteria were directly related to drinking. Although a correlation was observed, the data does not prove causation.

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Yiping Han, a professor in dental medicine and microbiology at Columbia University in New York City, who was also not involved in the research, told CBS News that the oral microbiome could be influenced by several factors. These include dental care, diet, and even income level. She added that it’s unclear how much the heavy drinkers' consumption of alcohol varied from person-to-person. Individuals who drank significantly more than others could be notably different.

But Ahn is confident that her research shows alcohol’s influence on the microbiome.

"It is pretty much safe to say that alcohol influences the oral microbiome, because the other way doesn't make sense," she told TIME. "[Your] oral microbiome makes you drink more alcohol? That doesn't make sense. It's more likely from one direction: that alcohol influences the microbiome."

Read the full study at microbiomejournal.biomedcentral.com.

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