More Evidence Linking Gum Disease and Heart Disease
Credit: Human heart diagram via Shutterstock

People with gum disease show a higher risk for heart problems, but it's been controversial whether bacteria in the mouth can indeed cause heart disease, or whether people with worse oral health just tend to have worse heart health, as well. Now, a new study in mice provides more clues to these bacteria in action.

The researchers infected mice with four types of bacteria that cause gum disease, and then tracked the spread of the bacteria over six months. Results showed that the bacteria traveled from the mouth to the heart and the large artery called the aorta; this increased the animals' cholesterol levels and inflammation, which are risk factors for heart disease. The bacteria also migrated to the kidney, lung and liver.

The results show that the same bacteria that cause gum disease also promote heart disease, said the researchers, who presented the findings Sunday (May 18) in Boston at the annual meeting of the American Society for Microbiology. [Chew on This: 8 Foods for Healthy Teeth]

There are two forms of gum disease, gingivitis and periodontitis. Both types are common among adults in the United States. The bacteria that causes gum disease can enter the bloodstream during dental procedures and tooth brushing, the researchers said.

Numerous studies have observed that people with gum disease have higher risks for heart disease, but many experts have been skeptical about whether these bacteria may actually be causing heart disease. Gum disease and heart disease share several common risk factors, including cigarette smoking, older age and diabetes, and these factors could explain why people with gum disease are likelier to have heart disease, too. 

In 2012, the American Heart Association reviewed more than 500 studies and concluded that common factors cannot explain the link between the two diseases. However, there wasn't enough evidence at the time to conclude that one causes the other, the association said in a statement.

The researchers of the new study said their results could change things.

"Our hope is that the American Heart Association will acknowledge causal links between oral disease and increased heart disease. That will change how physicians diagnose and treat heart disease patients," said study researcher Irina Velsko, a graduate student at the University of Florida's College of Medicine.

However, the new findings do not close the case. Because the study was done in animals, the findings may not apply to humans. Also, researchers need to conduct more studies to discover if treating people's gum disease could help prevent heart problems.

Oral bacteria have been linked to many conditions other than heart disease. Studies have associated gum disease with an increased risk of type 2 diabetes, respiratory and kidney disease, erectile dysfunction, problems in pregnancy such as miscarriage and premature birth, and taking longer to become pregnant.

Email Bahar Gholipour or follow her @alterwired. Follow us @LiveScience, Facebook & Google+. Original article on Live Science.