As many as 700 species of bacteria live on our teeth and in our mouth, and just like the microbiomes inhabiting other parts of our bodies, they change in response to diseases and other health conditions.
Type 2 diabetes is the most common kind of diabetes, and estimated 29 million people in the US have the disease. A much smaller percentage of US children, about 0.25%, have type 2 diabetes, but the incidence has increased 30% since 2009, a worrisome trend. In type 2 diabetes, the body may make insulin, but doesn't use it properly, and since insulin metabolizes sugars consumed in the diet, sugar levels in the blood are increased and treatment is required to decrease them.
In a study to be published in PLOS ONE, a group of researchers from the Forsyth Institute in Cambridge, Massachusetts, and the Dasman Diabetes Institute in Kuwait, reported that the bacteria making up the oral microbiome of kids changed depending on the amount of sugar (glucose) in their saliva.
The study looked specifically at glucose in the saliva of 8,173 ten-year-olds and compared it with the bacteria present in the kids' mouths. Some of the children were diabetic, but most of the saliva samples, about 98%, had normal levels of less than 1 mg/dL glucose—indicating that if they were diabetic, their sugar levels were well-controlled at the time of the study.
Both the total bacteria present and the number of almost every bacterial species tested were decreased in samples with high salivary glucose. That might sound like a good thing, but most of the bacteria that normally lives in our mouths is protective. These protective bacteria stop the disease-causing bacteria from sticking to surfaces in the mouth—the first step in causing cavities and other dental issues. When their levels drop, disease-causing microbes have a better chance of getting a stronghold in the mouth and causing problems.
High-glucose patients had, on average, a 62% decrease in the presence of 27 bacterial species, compared with bacteria present in samples where the saliva glucose was normal. And the overall number of bacteria in 35 of the 42 bacterial species evaluated was significantly lower.
Since a change in the oral microbiome can affect mouth health, the kids teeth and gums were also checked as part of the study. Children with high salivary glucose had increased gum redness and twice the frequency of cavities as the kids with normal saliva glucose.
Increased saliva glucose may be the root cause of changes in the oral microbiome, according to the study, led by J. Max Goodson, from Forsyth Research Institute.
About 34% of the children in the study were obese, weighing more than 95% of kids their age and height.
Obesity and high blood sugar aren't just signals of diabetes, they're also characteristics of metabolic syndrome, a group of risk factors that raises risk for diabetes, heart disease, stroke, and other health problems.
Obesity has been associated with changes in the oral microbiome, including high proportions of Firmicutes bacteria and reduced proportions of Bacteroidetes. Those same changes in bacterial populations were seen in children with high salivary glucose in the PLOS ONE study. Streptococcus mutans is the bacteria mainly responsible for tooth decay, and it is a type of Firmicutes.
The study supports the idea that high blood sugar, associated with obesity and type 2 diabetes, results in high saliva glucose. That glucose makes the saliva more acid by decreasing the pH. The acidity, in turn, decreases the overall bacterial counts of the oral microbiome and changes the frequency of certain bacterial species to those kinds that like acidic environments, like the cavity-causing S. mutans.
The end result is an increase in types of bacteria that cause cavities and gum inflammation.
The study highlights the importance of dental care in people with certain conditions, like diabetes, obesity, and metabolic syndrome. People with these disorders should practice good oral hygiene and receive frequent dental care to help offset their increased risk for cavities and gum disease.