Possible cause and effect relationship between cardiovascular diseases and red meat

Possible cause and effect relationship between cardiovascular diseases and red meat

In an article entitled, “Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis,” published in April 7, 2013, issue of Nature Medicine (doi:10.1038/nm.3145), the lead author Robert A Koeth with twenty two other associates from ten research groups discovered a link between cardiovascular disease and the nutrient l-carnitine found in red meat (Red meat includes the meat of most adult mammals like beef, veal, lamb, mutton and pig and some fowl like duck). They studied the disease-promoting effects of l-carnitine in mice and discovered that the aforementioned nutrient increases the risk of cardiovascular diseases following metabolization by stomach microbes into the compound trimethylamine N-oxide (TMAO). TMAO is capable of damaging arteries supplying blood to the heart and brain. The study tested the carnitine and TMAO levels of omnivores, vegans and vegetarians, and examined the clinical data of 2,595 patients undergoing elective cardiac evaluations. They also examined the cardiac effects of a carnitine-enhanced diet in normal mice compared to mice with suppressed levels of gut microbes, and discovered that TMAO alters cholesterol metabolism at multiple levels, explaining how it enhances atherosclerosis. The researchers found that increased carnitine levels in patients predicted increased risks for cardiovascular diseases and major cardiac events like heart attack, stroke and death, but only in subjects with concurrently high TMAO levels. In addition, the bacteria living in our digestive tracts are dictated by our long-term dietary patterns. A diet high in carnitine actually shifts human 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. However, this evidence is not sufficiently compelling to cause concern amongst the red meat industry and a balanced diet remains the best recommendation for meat lovers. While the paper makes some clever observations, the overall evidence that red meat is harmful-is not consistent with a broader body of evidence. [summarized by Samsad  Razzaque a graduate student in plant biotechnology lab, DU]

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