Chemical in Red Meat Linked to Heart Disease

A chemical found in red meat has recently been linked by scientists to the higher incidence of heart disease among the current population. A team of researchers from the US has identified a link between heart disease and a compound called carnitine, which is found in red meat and also as a supplement to popular energy drinks. The research is published online in the journal Nature Medicine.

The study, led by Stanley Hazen, M.D., Ph.D., Vice Chair of Translational Research for the Lerner Research Institute and section head of Preventive Cardiology & Rehabilitation in the Miller Family Heart and Vascular Institute at Cleveland Clinic, and by Robert Koeth, a student from Cleveland Clinic Lerner College of Medicine of Case Western Reserve University showed that bacteria living in the human digestive tract metabolize the compound carnitine and turns it into trimethylamine-N-oxide or TMAO, a metabolite that previous research has linked to the promotion of atherosclerosis in human. Furthermore, the research also found out that a diet high in carnitine also promotes the growth of the bacteria that metabolize carnitine, which can further compound the problem by an increased production of the TMAO metabolite.

The researchers tested the carnitine and TMAO levels among omnivores, vegans and vegetarians as well as examined clinical data of 2,595 patients getting elective cardiac evaluations. Aside from that, the research team also conducted tests on how a carnitine-enhanced diet affects the heart in normal mice and compared it to mice with suppressed levels of gut bacteria. The team discovered that the TMAO changes cholesterol metabolism at several levels.

The researchers discovered that increased carnitine levels in patients is linked to increased risk of heart disease as well as other major conditions such as heart attacks, strokes, and death, but only in the subjects with high levels of TMAO. And also, the researchers found specific gut microbe types associated with TMAO levels as well as dietary patterns. The study showed that the baseline TMAO levels were significantly lower among vegetarians and vegans than among omnivores. Interestingly, the vegans and vegetarians did not produce significant levels of TMAO even after consuming a large amount of carnitine. This had a quite opposite effect on omnivores consuming the same amount of carnitine.

According to Dr. Hazen, “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.”

Source: Cleveland Clinic (2013, April 7). New link between heart disease and red meat: New understanding of cardiovascular health benefits of vegan, vegetarian diets. ScienceDaily. Retrieved April 15, 2013, from


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