Red meat’s effect on your heart

Medical experts have long included red meat near the top of their list of foods one should limit to avoid heart disease. The high amounts of artery-clogging cholesterol and fat in red meat definitely make it a menu item to reduce or eliminate for a heart-healthy diet. But a recent study indicates that there may be more to the problem of red meat than just the obvious.

“Cholesterol, saturated fat and salt only account for a tiny little piece of the risk,” said study co-author Dr. Stanley Hazen of the Cleveland Clinic in a statement. The study suggests that intestinal microbes, or “gut bacteria,” may play a significant role as well.

Red meat, as well as some energy drinks and body-building supplements, contains a nutrient called L-carnitine. The study found that when bacteria in the digestive system of a non-vegetarian feed on L-carnitine, an artery-hardening chemical is formed as a byproduct. According to the researchers, the presence of this byproduct, called trimethylamine N-oxide or TMAO, is a solid warning sign of a potential heart attack or stroke, when found in high levels.

Interestingly, test subjects in the study who were long-established vegetarians or vegans produced almost no TMAO, even after consuming red meat for the study. Only subjects who already include red meat in their regular diet showed noticeable levels of TMAO in their blood. This result was attributed to differences in the digestive tract bacteria make-up between those who regularly consumed meat and those who did not.

“The composition of bacteria living in our digestive tracts is dictated by our long-term dietary patterns,” said Dr. Hazen. “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, which helps promote atherosclerosis.”  Atherosclerosis, or “hardening of the arteries,” is a disease in which plaque builds up in the arteries, restricting blood flow.

Researchers hope that testing for TMAO can give physicians new insight in determining a patient’s heart disease risk. The American Heart Association (AHA) named this discovery as one of their top 10 advances in heart disease and stroke science for 2013. 

“Regardless of how atherosclerosis develops, the important thing is to maintain an overall heart-healthy lifestyle to help prevent heart disease,” says Dr. Kunal Bodiwala, a cardiologist with Advocate Medical Group in Normal, Ill. “Following the AHA dietary guidelines, which are rich in fruits and vegetables, whole grains and fish while conservative with sugar and salt, is the best way to modify your eating habits. Don’t smoke, get regular exercise, and manage your weight, blood pressure, cholesterol and blood sugar. All these things together are your strongest defense.”