High levels of a compound found in the gut of meat eaters have been linked to an increased risk of fatal heart problems.

Patients with high levels of trimethylamine N-oxide, or TMAO, were six times more likely to die or suffer a stroke or heart attack say researchers at the Cleveland Clinic, according to a report by WebMD. TMAO is produced during digestion by intestinal bacteria from foods rich in choline and L-carnitine, including eggs, red meat, and dairy products.

The TMAO threat was twofold: TMAO was shown to increase cholesterol buildup in artery walls, which leads to plaque formation and hardening of the arteries, and high levels of TMAO also led to higher incidence of artery blockage via blood clotting.

Cleveland Clinic researchers studied patient information that showed people with the highest levels were almost twice as likely to die within seven years. They followed 530 people in Cleveland and 1,600 patients in Switzerland. Patients in both groups were admitted to the ER after complaining of chest pains.

These groups were monitored for several years for heart attack, stroke, or death. Patients at the Cleveland Clinic with high TMAO levels were six times more likely to die or have serious heart problems within 30 days and nearly twice as likely to die within seven years.

The Swiss patients with high levels of TMAO had a 57 percent increased risk of a heart-related health crisis and a 60 percent increased risk of death within one year.

Lead researcher Dr. Stanley Hazen, chair of cellular and molecular medicine at the Cleveland Clinic's Lerner Research Institute, confirmed the findings: "A high TMAO level predicted who went on to experience a major cardiovascular event." Hazen also acknowledged that TMAO formation appeared to trigger blood-cell clotting, and blocked arteries. "If you infuse TMAO into the blood, you can show that platelets become hyper-responsive," he said. "A lower degree of stimulus can produce a more pronounced and more robust degree of platelet activation and more clot formation."

Hazen noted that TMAO appeared to outperform troponin, a traditional heart-attack blood marker. Troponin is a protein released by damaged heart-muscle cells, and is considered the best biomarker for detecting a heart attack.

About 31 percent of Cleveland patients who tested high for TMAO but negative for troponin had a heart-related crisis within 30 days, and about 37 percent within six months, the study found.

"A lot of people present with chest pain, and they still have not had a high cardiac enzyme," Hazen said. "It can take several hours for levels to go up. That's why they are asked to sit and wait in an observation unit, to see whether or not they are actually having a heart attack."

Since TMAO testing is widely available and inexpensive, in the future, after further study, doctors might add TMAO as a blood marker in their arsenal to detect potential heart problems, Hazen added.

Despite the mixed results from the two groups the benefits of limiting animal protein shouldn't be underestimated, the researchers said.

The new study was published in the European Heart Journal.