Study Offers New Insight into Red Meat, Cardiovascular Risks

Dorian Martin Health Guide
  • Like many men of his generation, Dad grew up a meat-and-potatoes guy.  Pot roast, brisket, stew – I remember eating those meals a lot while growing up because Mom wanted to make dishes that Dad enjoyed.  One of his favorite meals involves a grilled New York strip steak, served medium rare. In fact, I’ve got two of them defrosting in the refrigerator so we can enjoy them while watching the final game of March Madness. However (since I’m the chef in this household), I make sure that we don’t eat red meat too often. The protein in our meals more often tends to be chicken and (increasingly) fish.

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    And it turns out that change in our eating patterns may be a really thing! A new study by researchers from the Cleveland Clinic showed that red meat has carnitine, a compound found in red meats (beef, venison, lamb, mutton, duck and pork) as well as energy drinks, morphs thanks to bacteria in the digestive tract into trimethylamine-N-oxide (TMAO). This substance has previously been linked to promoting atherosclerosis (hardening or clogging in the arteries).


    The researchers looked at the levels of both carnitine and TMAO in omnivores, vegans and vegetarians. They also analyzed data from 2,595 patients who had elective cardiac evaluations. In a third part of the study, they studied the cardiac effects caused by a carnitine-enhanced diet in normal mice as well as mice that had suppressed levels of gut microbes. This last part of the study helped the researchers find out that TMAO changes the water cholesterol is metabolized at several levels, thus causing atherosclerosis to increase.


    The researchers also found eating a lot of red meat (or consuming a lot of energy drinks that have carnitine added) actually causes more of the bacteria to live in the digestive tract, thus leading to more artery-clogging TMAO to be produced. Furthermore, higher levels of carnitine and concurrently high TMAO levels indicates an increased risk for cardiovascular disease, including heart attacks, stroke and death.


    So what about the vegans and vegetarians? The researchers found that these groups of study participants didn’t produce significant levels of TMAO, even after eating a large amount of carnitine.


    “The bacteria living in our digestive tracts are dictated by our long-term dietary patterns,” said Dr. Stanley Hazen, the vice chair of the Lerner Researcher Institute, the section head of the Preventive Cardiology and Rehabilitation in the Cleveland Clinic’s Miller Family Heart and Vascular Institute Hazen and the study’s lead author. “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.”


    Hazen also called for increased study on the effect on the human body of additional carnitine through supplements and energy drinks. “Carnitine is not an essential nutrient; our body naturally produces all we need,” he says. “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.”


  • So what should you do if you’re like my dad and love your red meat but want to lower your risk of cardiovascular disease through diet? I’d suggest limiting the amount of red meat that you eat each week and focus your meals more on vegetables, fruits legumes and seafood.  And if you haven’t already, read my sharepost about a major study that highlighted the benefits of a Mediterranean diet (which is the type I’m describing).

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    Cleveland Clinic. (2013). Study offers new understanding of cardiovascular health benefits of vegan, vegetarian diets.

Published On: April 08, 2013