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Maybe it's not really cholesterol from that big, juicy steak that's linked to heart disease. Instead, it could be a compound in red meat called carnitine, which does a number on our gut bacteria if we eat too much meat too often, suggests intriguing new research.
Carnitine seems to have a profound effect on certain bacteria in the intestine; these in turn produce a chemical linked to clogging of the arteries and heart disease. The more meat we eat, the more it changes our intestinal bacteria, making us even more susceptible to the artery-clogging by-products.
By contrast, vegetarians and vegans who were given a generous serving of red meat as part of the new study didn't produce the same harmful chemicals in their bloodstream as did the meat eaters, most likely because their digestive bacteria are different.
This "surprising new explanation of why red meat may contribute to heart disease," comes from a study by researchers with the Cleveland Clinic who conducted tests on both humans and mice, the New York Times reported.
The study was published in the journal Nature Medicine and was funded by the National Institutes of Health.
Carnitine is abundant in red meat like beef and pork. During digestion, carnitine gets converted by intestinal bacteria into a chemical called TMAO. TMAO then gets into the bloodstream and promotes atherosclerosis, or a thickening of the arteries, perhaps by making it difficult for the body to get rid of excess cholesterol, researchers theorize.
"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," said lead author Stanley Hazen, M.D., an atherosclerosis expert. "Meanwhile, vegans and vegetarians have a significantly reduced capacity to synthesize TMAO from carnitine, which may explain the cardiovascular health benefits of these diets."
Carnitine plays an important role in helping the body transport fatty acids into cells to be used as energy, the Wall Street Journal explained, which is why carnitine is added to some energy drinks and bodybuilding supplements - something that concerns Hazen. A typical energy drink could have more carnitine than a porterhouse steak, he said.
Other foods, such as milk, fish and chicken, contain small amounts of carnitine, but red meat contains the most. In general, the redder the meat, the more carnitine it contains, according to the National Institutes of Health. For example, four ounces of ground beef contains 87 to 99 mg. of carnitine, compared to a four-ounce cooked chicken breast, which contains 3 to 5 mg.
In the study, Hazen and his team of researchers tested the carnitine and TMAO levels in omnivores, vegans and vegetarians, and looked at blood test results of nearly 2,600 patients. Patients with high TMAO levels were at a higher risk for cardiovascular disease and more likely to suffer heart attacks, stroke and death, the researchers wrote.
This doesn't mean we should give up red meat entirely, said Hazen, but he admitted that his research has caused him to cut back on his own red meat consumption from several times a week, about 12 ounces at a time, to once every two weeks and no more than four to six ounces at a time.
As he told the New York Times: "I am not a vegan. I like a good steak."
Photo: Tavallai /flickr
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