Sweetened beverages disrupt the composition of the salivary microbiome

A recent study published in the journal Scientific Reports reports potentially pathogenic changes in oral microbiota after consuming sugar-rich beverages.

Oral Microbiome and Sugar-Sweetened Beverages

The oral microbiome includes more than 700 species of bacteria, as well as fungi, viruses, and other microorganisms. Disruption of the oral microbiome is associated with oral diseases such as periodontitis, and may also be linked to the development of diabetes, cardiovascular disease, and some cancers.

Saliva is often used to study the oral microbiome because it is readily accessible and stable. Additionally, saliva composition may reflect changes secondary to other microbiomes or external influences.

The researchers in the current study were interested in determining whether sugar-sweetened beverages, including soda and fruit juices, are detrimental to the salivary microbiota. The high acidity and sugar content of these beverages may promote tooth decay and support the growth of certain bacterial taxa that thrive in acidic environments. These bacteria may also produce more acid from the breakdown of carbohydrates.

Changes in biofilm composition affect the structure of the tooth surface where oral bacteria reside, thereby influencing the salivary microbiome. High levels of glucose and acid in saliva can also lead to inflammation and subsequent changes in the salivary microbiome.

Despite these documented associations, there is still a lack of research on how exactly sugar-sweetened beverages affect the oral microbiome.

Participant data were obtained from the American Cancer Society (ACS) Cancer Prevention Study-II (CPS-II) and the National Cancer Institute (NCI) Prostate, Lung, Colorectal, and Ovarian Cancer Screening Program. Saliva samples were collected from study participants between 2000 and 2002 and 1993 and 2001, respectively.

The current study recruited both cases and controls who did or did not develop head and neck or pancreatic cancer during follow-up, respectively. Each of these individuals was healthy at initial evaluation when they provided saliva samples.

In the PLCO group, a food frequency questionnaire was used to assess dietary intake over the past year. Sugar-sweetened beverages included orange or grapefruit juice, 100% fruit juices or fruit juice blends, and other sugar-sweetened beverages such as Kool-Aid, lemonade, and soda.

In the CPS-II group, study participants reported their consumption of soda and other caffeinated drinks, lemonade, punch, iced tea, and fruit juices of all types. Thus, in both groups, fructose and sucrose were the sources of fermentable sugar in the diet.

What did the study show?

The current study included 989 participants, 29.8% and 44.5% of whom did not consume sugar-sweetened beverages in the CPS-II and PLCO groups, respectively.

The highest sugar-sweetened beverage consumption in the CPS-II and PLCO groups was 336 and 398 grams per day, respectively, equivalent to drinking more than one can of juice or soda per day. Higher sugar-sweetened beverage consumption was associated with men, smokers, non-diabetics, and those who consumed more calories. In the CPS-II group, these people were also more likely to have a higher body mass index (BMI).

The higher the sugar-sweetened beverage consumption, the lower the richness of salivary microbiota α-diversity. Higher sugar-sweetened beverage consumption was associated with greater relative abundance of taxa from the Bifidobacteriaceae family, including Lactobacillus rhamnosus and Streptococcus tigurinus.

In contrast, genera such as Lachnospiraceae and Peptostreptococcaceae were less abundant. The higher the sugar-sweetened beverage consumption, the lower the abundance of taxa such as Fusobacteriales, including Leptotrichia and Campylobacter.

This correlation was not weakened after adjusting for organisms such as S. mutans that are associated with dental or gum disease, or those found in diabetes. Thus, other bacteria are also responsible for altering the composition of the oral microbiota.

Conclusion

Increased sugar-sweetened beverage consumption is associated with decreased bacterial richness and altered oral microbiota composition. Acid-producing bacteria become more abundant, while some commensals become less abundant with increased sugar-sweetened beverage consumption. This finding persisted after accounting for the presence of diabetes and oral diseases, which can independently alter oral microbiota composition.

When only individuals with subsequent cancer were analyzed, the associations became weaker, indicating that cancer risk factors were not responsible for these findings.

A decrease in the richness of the salivary microbiome may limit its stability and resilience to environmental changes, thereby predisposing a person to certain diseases. This may be explained by the damaging effects of exposure to high-sugar, high-acid beverages or by the compromised oral health of consumers, which may include deep gum pockets, dental caries, and increased plaque accumulation.

It should be noted that markers of oral diseases such as S. mutans did not influence the results of the study. Indeed, the presence of S. mutans may indicate the presence of dietary factors that promote its growth, as well as other cariogenic bacteria.

A decrease in commensal bacteria may negatively impact the innate immunity of the gums. The study results also indicate that Lactobacilli and Bifidobacteria may not be ideal choices for oral probiotics, as they produce acid that can potentially damage tooth structure.

Overall, the current study provides a better understanding of how microbiome-targeted dietary approaches can be used to prevent oral and systemic diseases.