Researchers Explore Link between Red Meat and Heart Disease

Researchers have found a compound - common in red meat products and popular energy drinks - that promotes the progression of a heart disease.

The compound, called carnitine, is broken down by bacteria in the gut to form trimethylamine-N-oxide (TMAO), a metabolite previously linked to atherosclerosis, or hardening of the arteries.

Also, people on a diet that has high levels of carnitine also have higher levels of gut bacteria that metabolize the compound to release TMAO, thus increasing the risk for atherosclerosis.

For the study, researchers assessed the levels of carnitine and TMAO in 2,595 patients who were undergoing elective cardiac evaluations. Study participants were omnivores, vegans or vegetarians. The study team also tested the effects of the compound on mice models.

Study results showed that high carnitine levels were a risk factor for many heart diseases like stroke, heart attack, etc. However, this increase was largely due to the presence of the metabolite TMAO rather than the compound itself. Interestingly, both vegans and vegetarians having high levels of carnitine did not have the carnitine-metabolizing bacteria in their guts.  

"The bacteria living in our digestive tracts are dictated by our long-term dietary patterns. A diet high in carnitine actually shifts our gut microbe composition to those that like carnitine, making meat eaters even more susceptible to forming TMAO and its artery-clogging effects. Meanwhile, vegans and vegetarians have a significantly reduced capacity to synthesize TMAO from carnitine, which may explain the cardiovascular health benefits of these diets," said Stanley Hazen, M.D., from Cleveland Clinic and lead author of the study.

Though, previous studies have shown that people with high levels of meat in their diet have high risk for heart disease, they couldn't explain a reason for the increase. High levels of fat or salt from these diets also weren't adequate in understanding the risk factors involved.

"Carnitine is not an essential nutrient; our body naturally produces all we need," Hazen said in a news release. "We need to examine the safety of chronically consuming carnitine supplements as we've shown that, under some conditions, it can foster the growth of bacteria that produce TMAO and potentially clog arteries."

The study is published in the journal Nature Medicine.

Other research has shown that certain gut microbes can raise the risk for obesity in people. One such study was recently published in The ISME Journal.

Atherosclerosis occurs when fat, cholesterol and other substances build up on the walls of arteries and form hard structures called plaque. These plaques then block the artery and cause major health problems, PubMed Health says. The plaques restrict blood flow that can result in damage or tissue death. Sometimes these plaques break in to smaller bits and block other smaller blood vessels or get in the lungs. Atherosclerosis is the leading cause of death for men and women in the U.S.