Red Meat and Heart Health: The Gut Bacteria Connection

There’s been a lot of debate over the years as to whether or not red meat consumption increases our risk of developing heart disease. In the past, much of the research has focused on the high levels of saturated fat and red meat, and their impact on blood cholesterol levels. A new study just published this month in Nature Medicine suggests a new mechanism: the difference in the type of gut bacteria between meat eaters and non-meat eaters.  A nice summary of the study was discussed recently on the National Public Radio show, Science Friday.

The main focus of this new study is a compound called L-carnitine, which is found in abundance in red meat. The intestinal bacteria found in omnivorous humans (compared to vegetarians or vegans) are more likely to metabolize L-carnitine into a compound called trimethylamine-N-oxide (TMAO).  High levels of TMAO accelerate the process of atherosclerosis.

The findings of this study are consistent with the well-known pattern of the Mediterranean diet, which places a great emphasis on plant-based foods, and recommends red meat only once or twice per month (see the pyramid diagram below). The Mediterranean diet is the pattern of eating among people in Italy, Greece, and other Mediterranean regions, that has been associated with protection against chronic disease, and greater lifespan.  This study has generated considerable outrage and debate, especially among proponents of high-meat diets, such as the Paleo diet. However, there is much more research about the health benefits of a Mediterranean eating pattern.

Once again, we’re just beginning to scratch the surface of the importance of the ecosystem living in our intestinal tract.  I recently reported that the normal flora living in our gut can have an influence on obesity and weight loss.  If the first hundred years of nutrition research has focused on identifying nutrient compounds, deficiency conditions, and toxicity, then the next hundred years could be looking more at the effects of normal flora on our health.

Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis.  Nature Medicine (2013) doi:10.1038/nm.3145.  
Published online
 07 April 2013

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