Flossing may be as important to heart health as exercise. Far from being an aesthetic issue, gum disease is linked to a number of health risks, including atherosclerosis, heart disease, and cancer.

The reason for the gums' disturbing connection to health problems hasn’t been totally clear. But now, researchers have discovered exactly why bacteria in your mouth are so troublesome for the body — they are able to evade our immune system.

With the host organism unable to fight off the bacteria that cause gingivitis, they can have far reaching effects, from mouth to blood vessels in the heart.

Bacteria have evolved certain mechanisms for dodging their hosts' immune systems, and Boston University School of Medicine researchers were interested in how the bacteria causing gingivitis, Porphyromonas gingivalis, were doing this. They suspected a specific fat molecule, lipid A, on the outside of the bacteria, which has two versions: One that activates a key regulator of the host’s immune system, and one that prevents it from activating.

The researchers found that P. gingivalis was using a version of the lipid A molecule that blocked activation of the host’s immune response, so the bacteria in gum disease are able to roam freely. With the host organism unable to fight off the bacteria, they can have far reaching effects, from mouth to blood vessels in the heart.

When the team infected mice prone to developing atherosclerosis with the strain of P. gingivalis that suppresses the host immune response, the mice were even more affected by inflammation and fatty buildup in the arteries.

What makes gingivitis so dangerous, according to the authors, is that the bacterium that causes it is able “…to evade host defenses and establish chronic infection leading to persistent systemic low-grade inflammation.”

And it’s this chronic inflammation that seems to be the cause of many different diseases and disorders, from heart disease to cancer to depression.

So the next time you consider procrastinating about flossing, think not just of better breath and healthier teeth, but of reducing the population of a type of bacteria that cause problems throughout the body.

Though it’s a little unnerving that bacteria in the mouth could affect body parts that are relatively far away, it’s also heartening to know that something as simple as brushing your teeth or a cleaning at the dentist could protect your heart.

The research is published in the open access journal PLOS Pathogens.