For the second time in a matter of weeks, a group of researchers reported a link between the food people eat and bacteria in the intestines that can increase the risk of heart attacks.

Two weeks ago, the investigators reported that carnitine, a compound found in red meat, can increase heart disease risk because of the actions of intestinal bacteria. This time they reported that the same thing happens with lecithin, which is abundant in egg yolks.

The lecithin study, published Wednesday in The New England Journal of Medicine, is part of a growing appreciation of the role the body’s bacteria play in health and disease. With heart disease, investigators have long focused on the role of diet and heart disease, but expanding the scrutiny to bacteria adds a new dimension.

“Heart disease perhaps involves microbes in our gut,” said the study’s lead researcher, Dr. Stanley Hazen, chairman of the department of cellular and molecular medicine at the Cleveland Clinic Lerner Research Institute.