by Bianca Garilli, ND
It is well known that gut dysbiosis impacts various aspects of human health, from cardiovascular disease to asthma.1 Bacterial composition in the digestive tract can be influenced by many aspects of daily life: stress levels, environmental exposures, and dietary habits, including alcohol consumption, to name a few.1-2 The literature also suggests that alcohol intake may play a role in the makeup of human oral microbiota through several mechanisms including direct cytotoxic effects on bacteria, changing the saliva-bacterium interactions, and by providing substrate for bacterial metabolism.2 Changes to oral microbiota composition may lead to dysbiosis within the oral cavity, resulting in increased risk for both oral and systemic disease processes including periodontal disease, dental caries, gastrointestinal cancers, and cardiovascular disease.2
Less well understood is how the quantity and types of alcohol ingested may influence the oral microbiome composition. A large, cross-sectional study of US adults published in Microbiome aimed to learn more about this relationship. Participants (N=1,044) originated from the American Cancer Society Cancer Prevention Study II (CPS II) Nutrition cohort and the National Cancer Institute Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort.2 Participants were categorized as non-drinkers, moderate drinkers (> 0 but < 1 drinks/day for women, and > 0 but < 2 drinks/day for men) or heavy drinkers (> 1 drink/day for women, >2 drinks/day for men).2 Additionally, participants who consumed a single form of alcohol exclusively (wine, beer, liquor) were defined as wine drinkers, beer drinkers, or liquor drinkers, respectively.2
Participant’s oral wash samples were collected after swishing vigorously with 10mL of mouthwash for 30 seconds and then expectorating into a specimen tube.2 16S rRNA gene sequencing was performed on the bacterial genomic DNA samples and analyses performed.2 Results from the analyses were studied alongside comprehensive demographic and lifestyle information gathered via questionnaires.2
The effects of alcohol consumption on the oral microbiome were assessed by comparing subjects in the moderate and heavy categories to non-drinkers and also for the various types of alcohol consumed.2
Quantity of alcohol consumed – results and comments:2
- Increasing levels of alcohol consumption were associated with a decreased abundance of the order Lactobacillales (LBS), which is important in maintaining a healthy oral cavity pH; an abnormal pH reduces the antimicrobial properties of saliva. Therefore, when LBS is lower than normal, there may be an increased opportunity for growth of pathogenic bacteria and/or bacteria associated with dental caries and periodontal disease.
- In fact, increased levels of potentially pathogenic bacteria and bacteria associated with dental caries were found with higher levels of alcohol consumption; these included Aggregatibacter, Actinomyces, Kingella, Leptotrichia, Cardiobacterium, Bacteroidales (G-2) and Prevotella.
- An increase in the above noted bacterial communities may be associated with various disease processes including: periodontal disease, infective endocarditis, and various human infections
- It may also be possible that various dysbiotic bacteria produce acetaldehyde from the consumed ethanol; the World Health Organization (WHO) has categorized acetaldehyde as a group 1 human carcinogen (Lactobacillus, which was found to be decreased in alcohol drinkers, is known to metabolize acetaldehyde and thus, when found in lowered quantities may result in higher levels of acetaldehyde).
Type of alcohol consumed – results and comments:2
- Drinkers of wine may have a higher diversity and different microbial profile than non-drinkers. Specifically, wine drinkers had a lower abundance of phyla Bacteroidetes and Firmicutes, and family Peptostreptococcaceae.
- The increased variety in the wine drinkers’ oral microbiota supports previous research indicating possible antimicrobial properties of wine.
- Further research on the effects of strictly drinking one form of alcohol over another are needed to fully understand the impact of each on the oral cavity microbiome.
Why is this Clinically Relevant?
- In addition to potential increased risks for chronic disease (e.g. liver disease, cancers), moderate and heavy alcohol consumption may impact the oral microbiome, which may have implications for systemic health and disease risk including periodontitis, dental caries and infective endocarditis2
- Wine drinkers, vs. beer or liquor drinkers, appear to have distinct oral microbial community structure and diversity2 Dysbiosis in the oral cavity may play a role in alcohol-related carcinogenesis through increased levels of acetaldehyde
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- Carding S, Verbeke K, Vipond D, Corfe BM, Owen LJ. Dysbiosis of the gut microbiota in disease. Microb Ecol Health Dis. 2015;26:26191.
- Fan X, Peters BA, Jacobs EJ, et al. Drinking alcohol is associated with variation in the human oral microbiome in a large study of American adults. Microbiome. 2018;6(1):59.