The L-carnitine, a compound abundant in red meat and often added as a complement to many energy drinks, could be promoting atherosclerosis according to research published in Nature Medicine. The study, by researchers at the Cleveland Clinic (USA), shows that the bacteria in the human digestive tract metabolize L-carnitine, making trimethylamine-N-oxide (TMAO), a metabolite that has been linked since 2011 with the development of atherosclerosis in humans. 

In addition, research has found that a diet high in L-carnitine promotes the growth of bacteria that metabolize, compounding the problem by producing even more amounts of TMAO that eventually clog arteries and trigger cardiovascular disease.

Experts saw that patients with elevated levels of L-carnitine appeared to have increased risk of cardiovascular disease and cardiac events such as heart attack, stroke and death, but only in those subjects who also had high rates of TMAO. There was a relationship between the levels of TMAO and the type of diet, and events were significantly lower in vegans and vegetarians than in omnivores. Surprisingly, vegetarians and vegans did not generate significant amounts of TMAO producing microbes even after consuming a large amount of L-carnitine, while it did occur in omnivores who consumed the same amount of carnitine.

This data may explain why diets rich in red meat are associated with increased cardiovascular risk, as the cholesterol and saturated fat in red meat does not seem sufficient to explain the increased cardiovascular risks. Until now this discrepancy has been attributed to genetic differences, a high-salt diet that is often associated with the consumption of red meat or possibly even the cooking process.

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