Study examines how diet quality impacts oral microbiome

A University at Buffalo study using a sample of postmenopausal women is the first to examine the association between diet quality and the oral microbiome.

The research, published earlier this year in the Journal of Nutrition, reports that women who followed healthier diets had lower abundance of certain oral microbiome bacteria, including Streptococcus gordonii, which can promote gum disease, and Cardiobacterium species, which are associated with heart infections.

For the study, researchers measured the overall diet quality of 1,175 postmenopausal women by estimating the Healthy Eating Index 2020 (HEI-2020) scores for each woman from a food frequency questionnaire. HEI-2020 is a measure of diet quality, reflecting a person’s adherence to the 2020 Dietary Guidelines for Americans.

HEI-2020 scores were associated with the composition, but not the diversity, of the oral microbiome. However, individual HEI-2020 components were associated with both its diversity and composition, suggesting that specific dietary components may have more impact on the diversity and composition of the oral microbiome than overall diet quality.

For example, intake of total vegetables and total protein foods was associated with more diverse oral microbiomes, while intake of dairy and added sugar was associated with less diverse oral microbiomes.

“While previous studies have explored how specific foods or nutrients relate to the oral microbiome, people don’t eat nutrients in isolation—foods are consumed together, their intake can be correlated, and their health effects may be interactive,” says the study’s first author, Yihua Yue, Ph.D., who worked on the research while completing her doctorate in epidemiology from UB’s School of Public Health and Health Professions.

“That’s why we focused on overall diet quality to capture a more comprehensive view of dietary intake,” adds Yue, who is now a postdoctoral research fellow at the Cleveland Clinic. “We wanted to understand how diet quality, as assessed by the Healthy Eating Index, was associated with bacteria present in their oral cavity. We wanted to see if the diversity and composition of the oral microbiome varied significantly in those with high quality versus low quality diets.”

Researchers have observed associations between the prevalence of periodontal disease and increased risk or odds of diseases such as cancer, cardiovascular disease and other chronic diseases with inflammation indicated in their etiology, such as age-related macular degeneration, according to Amy Millen, Ph.D., corresponding author and associate professor in the Department of Epidemiology and Environmental Health at UB.

But there’s debate as to whether this association is causal.

“What we do know,” Millen says, “is that nutrition is a risk factor for many diseases with inflammatory etiologies. Our research team has been working to understand if nutrition, both specific nutrients and diet patterns, is a risk factor for periodontal disease. As oral bacteria play a causal role in the development of periodontal disease, we thought that if we observed associations between dietary quality and the oral microbiome this might provide additional evidence of the role of diet in the development of periodontal disease or other outcomes such as dental caries.”

The HEI-2020 includes 13 components, each representing different aspects of diet quality. While higher, meaning more favorable, scores for individual components are generally recommended and considered beneficial for overall health, this does not necessarily imply that these 13 components exert consistent effects on the oral microbial composition, Yue says.

“Our findings suggest that the recommendations of the Dietary Guidelines for Americans for certain types of food—particularly for intake of sugar, vegetables and seafood and plant-based protein—may play a role in shaping the oral microbiome,” she adds. “These findings provide evidence for the U.S. Department of Agriculture to consider and evaluate for the relevance of the HEI-2020 in the context of oral health.”

The authors note that while the sample includes only postmenopausal women, the findings are particularly relevant to this group, which has an increased risk of gum disease and tooth loss due to hormonal changes and aging. Future studies may benefit from including participants with a broader range of dietary habits and lifestyle factors.