Peripheral artery disease patients who had high blood levels of a digestive byproduct were significantly more likely to die during a five-year study released Wednesday.

The digestive byproduct — trimethylamine N-oxide — is produced by gut bacteria breaking down red meat, eggs and other meat products in the traditional Western diet.

Previous research has associated TMAO with narrowing of the heart’s arteries, or coronary artery disease.

“Improving our understanding of the functional changes that link gut microbes with PAD development may help us improve the selection of high-risk PAD patients, with or without significant coronary artery disease, who likely need more aggressive and specific dietary and medical therapy,” said W. H. Wilson Tang, M.D., study lead author and a professor in medicine at the Cleveland Clinic in Ohio.

After studying 821 patients with PAD who received a screening test for coronary artery disease and blood tests to determine TMAO levels, researchers found that the incidence of short- and long-term death progressively increased as blood levels of TMAO rose. Compared to patients with the lowest levels, those with the highest levels of TMAO were 2.7 times more likely to die of any cause.

Although the results don’t prove that high TMAO levels caused the deaths, they demonstrated an association.

About 8.5 million Americans have PAD, which occurs when fat and other substances accumulate in the arteries of the legs, arms, head or abdomen — restricting or blocking blood flow. The legs are affected most often, and common symptoms include pain or cramping during walking or other movement that disappear with rest.

PAD often can be treated with lifestyle changes, such as stopping smoking; increasing exercise; losing weight; controlling high blood pressure, cholesterol and sugar; and eating a heart-healthy diet.

The study is published in the Journal of the American Heart Association.