The longstanding belief that heart disease is caused by lipids ingested through high-cholesterol, fatty foods is being challenged by research out of the University of Connecticut that’s suggesting bacterial fats, not dietary ones, are responsible for cardiovascular complications.

Using chemical analysis of atheromas collected from Hartford Hospital patients, Frank C. Nichols, DDS, PhD, and colleagues noticed a presence of lipids that were chemically removed from those associated with animals. The molecules, instead, are linked to a bacteria known as Bacteroidetes, which are characterized by branched chain fatty acids and odd numbers of carbons.

“I always call them greasy bugs because they make so much lipid,” Nichols said in a release from the University of Connecticut. “They are constantly shedding tiny blebs of lipids.”

Nichols and his team linked the Bacteroidetes to atherosclerosis in cardiovascular patients by using weight differences between bacterial and human lipids and modern mass spectrometers  to measure the quantity of the Bacteroidetes, according to the study, which was published in the Journal of Lipid Research. Since the bacterial fats are non-native to the human body, the researchers said the chemical differences between Bacteroidetes and human lipids could be the reason they cause disease.

In the past, scientists’ belief that heart disease was triggered by a diet rich in fats was questioned by the fact that in studies, some patients who ate high-cholesterol diets with plenty of eggs, fatty fish, butter and meat didn’t develop heart disease, according to the release. If the immune cells that naturally adhere to blood vessel walls don’t recognize the bacterial lipids, they could react to the foreign entities negatively, raising red flags in the body. The authors wrote that lipid-processing enzymes also break down these new fats, supercharging the inflammation.

According to the research, the bacteria themselves aren’t inherently dangerous. They remain largely in the mouth and gastrointestinal tract, but the lipids they produce can easily diffuse into the bloodstream.

The release states the team’s next moves involve analyzing thin slices of atheroma to distinguish where these bacterial fats are accumulating.