open mouth graphic that has words inside that say Start Here
Category: Gut Health, Health Magazine

Title:The Mouth and the Microbes

Author: Jane Varner Malhotra
Date Published: November 3, 2020

Where else to begin a discussion of the gut than the gateway? Besides the place where food gets chewed, and words get spewed, the oral cavity hosts its own unique, complex microbiome that scientists are just beginning to understand. A dark, moist environment, it is a moving landscape of varying soft and hard surfaces like the fleshy insides of the cheek, the teeth, tongue, and gums. The mouth offers a large, visible membrane that acts like a window pane into a person’s overall health.

A healthy mouth flora is complex. Most humans have several hundred species of bacteria inside the mouth, in addition to other microorganisms including viruses and fungi. A diverse collection of bacteria in the mouth seems to correlate with good overall health. When our health declines, so does this diversity.

“In conditions like type 2 diabetes, obesity, and metabolic syndrome, we have evidence that there are changes in microbiome composition and diversity,” says Chiranjeev Dash, associate professor of oncology and assistant director at Georgetown’s Office of Minority Health and Health Disparities Research.

What’s the connection? Is it that when we’re sick, our tiny organisms die off? Or do we get sick because for some reason our microorganisms are depleted or less diverse?

“We don’t know what’s causal here,” Dash notes. “We do know that the gut, oral, and lung microbiomes develop at a very early age, and that during our lives a person’s microbiome doesn’t change much—unless there’s a radical change in environment or diet, which can happen with migration, for example, or when a person develops cancer or chronic disease, or makes a major change in lifestyle. While there’s a large variability in microbiome diversity from one person to the next, if the environment and lifestyle remain unchanged, an individual’s micro- biome remains remarkably constant.”

Not many people go through life without lifestyle changes, especially in today’s world. What can our microbiome reveal about our past and what lies ahead?

“A lot of researchers are starting to believe that changes to gut microbiome associated with lifestyle—such as diet and exercise—might be involved in development of low grade inflammation and metabolic diseases like diabetes and high blood pressure in the future,” says Dash. But before we get too far down the esophagus, let’s back up a bit.

Reaching Out to Local Communities

In 2016, Dash and his colleagues launched a study focusing on oral health among medically underserved populations in Washington, D.C. The project, supported by a grant from the George E. Richmond Foundation, is led by Lucile Adams-Campbell, senior associate dean for community outreach and engagement, and professor of oncology at Georgetown Lombardi Comprehensive Cancer Center.

Located in the ever-evolving Navy Yard community in Southeast Washington, the Office of Minority Health’s faculty and staff have focused on reducing health disparities and improving health outcomes for residents within the metro area, including the 4.1 million residents of the District, Prince George’s, Montgomery, Arlington, and Fairfax counties, and the city of Alexandria. To accomplish these goals, Adams-Campbell and her colleagues have diligently engaged community members, offered educational outreach opportunities, and conducted research to determine effective health interventions.

“A lot of research was already being done on the gut microbiome, so we focused on the oral microbiome,” says Dash.

The nation’s capital has some troubling oral health disparities, particularly among African American males living in low-income communities, who experience higher rates of periodontal (gum) disease and missing teeth. African American men are also more likely to present with later stages of oral cancer, and have worse outcomes compared to other races.

Using salivary samples collected from more than 250 volunteers, the team at Georgetown’s Office of Minority Health is aiming to characterize an oral microbiome profile for the community. By looking at the composition and diversity of organisms and comparing it to data from around the country, the scientists hope to better understand potential links to cancer, diabetes, cardiovascular disease, and poor nutrition.

“Your diet has a large influence on your microbiome, but what you get from your diet also depends on the microbes in your gut,” Dash says. Good nutrition is not as simple as eating healthy foods. The existing microbial environment in the body impacts what nutrients we can harness from whatever we eat.

In addition to poor nutrition, smoking and excessive alcohol play a negative role in oral health, as does a lack of exercise. Physical activity has benefits beyond weight loss, Dash asserts, as seen from research the team conducted among African American women at high risk for breast cancer. Although they didn’t always see a change in weight, women in the aerobic exercise group significantly reduced their metabolic risk factors for cancer within six months, compared to the group that did not exercise.

“We have enough evidence to show that physical activity has numerous benefits on health, but its effects on the oral microbiome are not well known,” says Dash. In the future, he hopes to study how exercise might affect the oral microbiome.

Dentistry and Oral Health

Retired D.C. dentist Salvatore Selvaggio, DDS (D’79), helps educate the community about oral health care, immunity, and aging.
Retired D.C. dentist Salvatore Selvaggio, DDS (D’79), helps educate the community about oral health care, immunity, and aging.

Early training as a research immunologist led Georgetown dental alum Salvatore Selvaggio (D’79) on a continuous path to understand connections between oral and whole-person health. For 34 years he operated a thriving practice in D.C., and after retiring in 2014, continues to support oral health in the community as a member of the District of Columbia Dental Society Foundation, offering lectures for Certified Nursing Assistant students and in-home health care workers on the importance of oral care for the older population.

“When a person develops periodontal disease—gum disease —the normal mouth bacteria get off balance,” Selvaggio says. Imbalance in the microbiome is known as dysbiosis. Abnormal oral bacteria overgrow, causing bleeding gums that pull away from teeth, breaking the normal seal and exposing a pathway to the bloodstream—essentially creating an open wound.

“Then cytokines—chemical messengers—get unleashed and can cause inflammation throughout the body,” he says. “Mouth bacteria don’t normally make it to the gut, because even though you swallow them, they get destroyed by the stomach acids. But some can survive past the stomach and get into the intestines, where they don’t belong. This can cause changes to the barrier cells lining them, causing ‘leaky gut.’ Alterations in barrier permeability can contribute to bowel inflammation and other problematic outcomes.”

He notes that taking antacids can contribute to this problem, especially when people overuse them, because it weakens the stomach’s power to kill off bacteria, letting more sneak by and disturb the intestinal lining.

At his dental practice, Selvaggio noticed a shocking decline in oral health among aging patients who moved into long-term care facilities.

“When people get into their older years, poor oral health can have serious consequences on their general health,” he says.

As Selvaggio explains, dry mouth from taking multiple medications, or a decreased swallowing reflex, can cause bits of food covered with disease-promoting microbes to enter the lungs, resulting in aspiration pneumonia. “Since our immune systems are less active as we age, the resulting hospitalizations and death are a major problem for residents of long-term care facilities.” Numerous studies have shown that by simply teeth brushing better, these dangerous outcomes can be reduced.

A host of other medical conditions have been linked to poor oral hygiene, such as diabetes and coronary artery disease.

“When people get pneumonia or viral infections, a lot of the mortality and morbidity comes from bacterial superinfections,” says Dash. “These are superimposed on top of a viral infection. We see a known association between periodontal disease and these bacterial superinfections.”

Periodontal disease can easily move from the mouth to the lungs because the pharynx and the larynx share a lot of the same territory and microbiome. Current research indicates that unhealthy respiratory systems may increase susceptibility to COVID-19, and the oral flora play a part in this dance.

The Value of Spit

A healthy, watery mouth is protective against infection, in addition to helping with taste, digestion, and swallowing.

Both Dash and Selvaggio expressed concern for cancer patients who undergo treatments that cause loss of saliva, resulting in a steep decline in oral health.

“We need our spit,” says the dentist. “I remember one patient who had radiation for neck cancer, but it killed off all his salivary glands. It was terrible.”

The team at the Office of Minority Health continues to search for answers on how the oral microbiome develops, especially around lifestyle, social determinants of health, and chronic disease. With the COVID-19 pandemic’s emergence and the devastation in communities of color, we know more than ever how critical immunology and virology are to community health.

Chelsea Burwell contributed to this story.

More from this Issue

maria gomez headshot

Founder, President, and CEO of Mary’s Center, a community health center serving over 60,000 people in the Washington, D.C. area through an integrated model of health care, social services,…

michael menchaca

Michael Menchaca (G’15) graduated from the School of Nursing & Health Studies Family Nurse Practitioner Program five years ago. After a relatively short stint at a traditional fee-for-service clinic,…

nurses working on dummy

In the midst of the COVID-19 crisis, Luci Baines Johnson (NHS’69, H’18)—daughter of President Lyndon B. Johnson and Lady Bird Johnson—and her husband, Ian Turpin, made a $1M gift to…