Of 28 Links Between Everyday Drinks and Mouth Bacteria, Alcohol Claimed 25

In the spring of 2018, researchers at NYU Langone went looking for a sign of drinking in the mouth. They had mouthwash samples from 1,044 adults who had joined two national cancer studies years earlier, and the signal was clear enough. Drinkers carried more Actinomyces and Neisseria and fewer Lactobacillales, the order that includes the lactobacilli sold as probiotics. Then the team tried to answer the question every drinker actually asks, whether it matters what’s in the glass, and ran out of people. Their sample held only 101 wine-only drinkers, 39 beer-only drinkers and 26 who drank only liquor, too few to split, and they said answering it would take more people.

Eight years later, the National Cancer Institute has run a study roughly five times that size. A preprint posted to medRxiv on October 9 by Lynn Ferro, Emily Vogtmann and colleagues pooled oral wash samples from 5,598 adults in three long-running federal cohorts: the Agricultural Health Study, the NIH-AARP Diet and Health Study and the PLCO Cancer Screening Trial. The team identified the bacteria in each sample with 16S sequencing, which resolves microbes down to the genus, and compared them against a year of self-reported intake in six everyday drink categories: coffee, tea, alcohol, sugar-sweetened drinks, artificially sweetened drinks and fruit juice. It is a single snapshot that hasn’t yet been peer reviewed, so it can show what goes together but not what came first. Within those limits, the result was lopsided.

Of the 28 statistically significant links the team found between a drink and a bacterial genus, 25 involved alcohol, mostly beer and liquor. Coffee accounted for the other three, including more Atopobium. Tea, soda, diet soda and juice produced nothing that survived correction for multiple comparisons. The overall effect is small: alcohol explained 0.86 percent of the variation in bacterial communities between people, less than smoking, age or education did, and all six drink categories together explained about 4 percent.

People in the top third of alcohol intake carried about 10 more distinct bacterial variants than non-drinkers (10.18 amplicon sequence variants, 95% CI 5.56 to 14.80). Anyone who follows gut research will read that as good news, since a more varied community in the colon usually signals a healthier one. The mouth doesn’t follow that rule so neatly, and the genera that rose with drinking show why. Heavy drinkers had 2.25 times the odds of carrying Megasphaera (95% CI 1.43 to 3.54) and 2.17 times the odds of carrying Peptostreptococcus (95% CI 1.63 to 2.89), which the authors describe as “a genus associated with periodontal disease.”

Lautropia, which the paper calls “a commensal bacterium often at lower abundance in dental diseases,” was 23 percent less abundant in the heaviest drinkers, and Streptococcus, a mainstay of the normal oral film, dropped too. So the shift runs toward genera that other research has tied to gum disease. The study never checked anyone for gum disease, though, and the cohorts recorded nothing about brushing, flossing or medications, any of which could move the same bacteria.

The glass matters, up to a point

The breakdown by drink type is where the 2018 question finally starts to get an answer. Compared with non-drinkers, the heaviest liquor drinkers carried about 15 extra variants (15.21), against about 7 for wine (7.04) and nearly the same for beer (6.72). Liquor was the only type linked to all three of the study’s diversity measures. Peptostreptococcus tracked with both beer (odds ratio 2.03) and liquor (1.76), and the drop in Streptococcus was steepest among liquor drinkers. Each estimate, however, compares one drink against no drinking at all. The paper reports no head-to-head test between beer, wine and liquor, so the ranking is a pattern in the data, not a proven difference.

For wine, the authors point to chemistry that has been studied in the lab for years: wine’s polyphenols “may suppress bacterial growth by inhibiting the formation of bacterial biofilm.” That would favor the grape over the grain, and it fits wine’s lighter footprint at the genus level. It doesn’t give wine drinkers a clean bill, because their extra variants sat right next to the beer drinkers’.

The liver isn’t the only place ethanol gets broken down

Mouth bacteria react to a drink because of one molecule. The body converts ethanol into acetaldehyde, mostly in the liver, and the NYU group suspected that acetaldehyde made by bacteria in the mouth could help drive the imbalance it found. Some oral microbes can make it right at the gumline. A 2019 study in Scientific Reports found that Streptococcus mitis, Streptococcus salivarius, Neisseria mucosa and Neisseria sicca all turn ethanol into acetaldehyde, with most strains producing the most at a mildly alkaline pH of 8.0, while Streptococcus mutans, the familiar cavity bacterium, made only a little. When another team sorted 100 human saliva samples by bacterial community, their ability to make acetaldehyde varied over a 30-fold range. How much a drinker’s mouth produces depends on who lives there.

That leaves one NCI result looking odd. The authors note that several Streptococcus species can turn ethanol into acetaldehyde, yet the genus as a whole fell with drinking, the opposite of what an earlier study reported. The data can’t rule out a simple explanation. 16S sequencing stops at the genus, and the Scientific Reports work found strong acetaldehyde producers inside Streptococcus living alongside a species that barely made any. So a falling total for the genus could hide a growing share of the producers. The authors’ own fix is shotgun metagenomic sequencing for species-level resolution. That method would also read the genes those species carry, though genes show what a microbe can do, not how much acetaldehyde a mouth actually makes.

Earlier federal research has already tied the mouth’s bacteria to cancer risk. For a 2018 study in JAMA Oncology, researchers used mouthwash collected from 122,004 participants in the American Cancer Society’s CPS-II cohort and the same PLCO trial, then compared the 129 people who later developed head and neck squamous cell cancer with 254 matched controls. People with more of the commensals Corynebacterium and Kingella before diagnosis had lower risk. Those aren’t the genera the NCI preprint flagged, and neither study shows that drinking-related shifts in mouth bacteria cause cancer. Even so, the NCI authors end by pointing to “a potential oral microbiome-mediated pathway for the relationship between alcohol and systemic disease risk,” and the JAMA Oncology results are a large part of why that idea deserves testing.

The new work was funded through the NIH intramural program and the National Cancer Institute, and its authors reported no conflicts of interest. Federal science on alcohol is getting more specific at the same moment federal advice on alcohol has become vaguer.

There’s a paper trail behind that vagueness. Under the Biden administration, the Department of Health and Human Services commissioned an Alcohol Intake and Health Study, whose draft warned that even one drink a day raises the risk of liver cirrhosis, oral cancer, esophageal cancer and injuries. In September 2025 its authors were told it would not go to Congress as planned. The alcohol industry had called the study biased and openly backed a rival National Academies report, some of whose panelists drew criticism over financial ties to alcohol makers. The Academies deny that industry shaped their conclusions. In January, the 2025–2030 Dietary Guidelines dropped the old definition of moderate drinking (two drinks a day for men, one for women) and told Americans only to “consume less alcohol for better overall health.” A trade coalition praised the guidelines as resting on “the preponderance of scientific evidence” and took aim at “anti-alcohol activist researchers.”

The sidelined study was published on June 9 in the Journal of Studies on Alcohol and Drugs. Amanda Berger of the Distilled Spirits Council called it “the product of a flawed, opaque and biased process.” Robert Vincent, a former SAMHSA alcohol-policy official, wrote in an accompanying editorial that “commercial interests” had interfered. He says he lost his job in a reduction in force aimed at federal staff working on alcohol policy. HHS maintains that “any characterization that the study was ‘shelved’ is inaccurate.” No document yet proves that the lobbying decided the outcome. The record does show an administration that promised to make America healthy putting out an alcohol guideline with no number in it, and the drinks trade applauding. Health-minded voters should hold it to that promise, whatever party it belongs to.

The NCI preprint doesn’t settle how much drinking does to the mouth, but it narrows the next question to one that can be measured: do beer and liquor drinkers carry more of the specific Streptococcus and Neisseria species that turn ethanol into acetaldehyde? The authors have named the method, and their samples come from cohorts the federal government already runs. Watch for the peer-reviewed version of this paper, for whether NCI goes back to those cohorts with species-level sequencing, and for the next five-year edition of the Dietary Guidelines, when HHS and USDA will decide whether Americans get a drink limit back.

Sources

1. medRxiv: Ferro, Vogtmann et al., “Associations between commonly consumed beverages and the oral microbiome in three US cohort studies” (2026 preprint)
2. medRxiv: Ferro et al., full text with beverage-type and genus-level results (2026)
3. JAMA Oncology: Hayes et al., oral microbiome and risk of incident head and neck squamous cell cancer (2018)
4. Scientific Reports: Tagaino et al., acetaldehyde production from ethanol by oral Streptococcus and Neisseria (2019)
5. Journal of Oral Microbiology: Yokoyama et al., salivary microbiota and acetaldehyde production (2018)
6. NYU Langone: Drinking affects mouth bacteria linked to diseases (Fan et al., Microbiome, 2018)
7. Anchorage Daily News: What a study at odds with Trump officials’ health guidance found on alcohol limits (2026)
8. UPI: Federal government pulls report linking alcohol use to cancer risks (2025)
9. News-Medical: Beer and liquor show more oral bacteria links than wine in a large US study (2026)