The connection between heart disease and red meat consumption has long been established. Saturated fat and cholesterol have taken the blame for the clogged arteries found in those who regularly include red meat in their diets. A research team at the Cleveland Clinic has identified another way red meat may contribute to heart disease. According to their study published April 2013, the compound carnitine, found in high concentrations in red meat, metabolizes in the human digestive tract to produce TMAO, trimethylamine-N-oxide. TMAO is a metabolic by-product that past research has found advances atherosclerosis, hardening of the arteries.

The study is one in a series of studies conducted at Cleveland Clinic to better understand the connection between atherosclerosis and digestive system microbes. The research team measured carnitine and TMAO levels in vegans, vegetarians and omnivores. A vegan diet contains no animal products; vegetarians do not eat meat, but they will consume dairy products. Omnivores eat both meat and vegetables. The data collected by the research team showed that subjects with both high carnitine and high TMAO levels were at greater risk of suffering cardiovascular disease, heart attack, and stroke.

The research also revealed that those who did not consume meat, the vegans and vegetarians, had significantly lower levels of the artery-hardening TMAO, even when they were fed the same amount of carnitine as those who regularly eat meat. These findings indicate that intestinal bacteria respond to long-term dietary behaviors. The bacteria in the intestines of those who do not eat meat lacked the microbes that convert carnitine into damaging TMAO.

Carnitine is a necessary compound produced by the liver and kidneys. It works to convert body fat into energy. It is often taken in pill form as a dietary supplement, and added to energy drinks, in the belief it will increase a person’s energy. Some manufacturers market carnitine supplements as a weight- loss product, although there is no evidence to support the claim that carnitine aides in weight loss. Dr. Stanley Hazen, who led the research, notes that the body makes all the carnitine it needs, and taking it in supplement form is unnecessary in most cases. Based on these new findings, it may even be harmful.

This study has important implication for those with family histories of heart disease. Controlling cholesterol levels with medication may not be enough to prevent the buildup of plaque in the arteries. Taking cholesterol-lowering statins does not give one free license to consume unlimited quantities of beef, pork, lamb and other red meats. A diet that minimizes carnitine consumption will actually change the way the body metabolizes this compound, and can protect the heart from the adverse effects of high TMAO levels.