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Egg yolks can add heart attack risk

NEW YORK — For the second time in a matter of weeks, a group of researchers has 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 have reported that the same thing happens with lecithin, which is abundant in egg yolks.

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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.

“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.

In the case of eggs, the chain of events starts when the body digests lecithin, breaking it into its constituent parts, including the chemical choline. Intestinal bacteria metabolize choline and release a substance that the liver converts to a chemical known as TMAO, for trimethylamine N-oxide. High levels of TMAO in the blood are linked to increased risks of heart attack and stroke.

To show the effect of eggs on TMAO, Hazen asked volunteers to eat two hard-boiled eggs. They ended up with more TMAO in their blood.

If they first took an antibiotic to wipe out intestinal bacteria, however, eggs did not have this effect.

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