A new study reinforces that red meat may cause heart disease. But it's not why you might think.
It’s well documented that eating less red meat can reduce heart disease risk. Doctors routinely encourage patients with atherosclerosis to swap red meat like beef for a more plant-based diet, and the virtues of vegan and vegetarian eating have proved heart healthy, according to several studies.
Forgoing red meat is also linked to a slew of other benefits. For example, vegetarians have better scores when it comes to blood sugar, blood fats, blood pressure, waist size and body mass—which together can reduce metabolic syndrome (prediabetes) risk, said a study inDiabetes Care.
But the mechanism leading to heart disease may actually be caused by something other than red meat’s saturated fat. It may be bacteria.
I know, it sounds weird.
New research published in the journal Nature Medicine found a specific gut bacteria that metabolizes the nutrient L-carnitine into a substance called TMAO (trimethylamine N-oxide). TMAO has been linked to the hardening of the arteries, also called atherosclerosis, because it’s believed to increase the absorption of LDL “bad” cholesterol.
The study found that when vegans and vegetarians ate red meat (I’m puzzled how they managed that one), researchers discovered they did not produce as much TMAO as meat-eaters, suggesting that people who eat plant-based foods don’t have as much L-carnitine-metabolizing bacteria in their gut.
“The bacteria living in our digestive tracts are dictated by our long-term dietary patterns,” Stanley Hazen, MD, and lead author said in a statement. “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.”
More questions than answers
We are continually discovering the importance of gut bacteria—a phenomena I personally find to be fascinating. Microbes, it seems, are intricately linked to more physical functions than we originally thought. Prior research has correlated the absence of gut bacteria, a byproduct of antibiotic use, to childhood obesity. Other studies have shown probiotics in the stomach regulate stress hormones, significantly affecting our mood.
But while this study indicates that bacteria influences various (or all?) of our body’s mechanisms, it also begs us to examine the nutrient L-carnitine. "Carnitine is found in red meat and gets its name from the Latin word carnis, the root of carnivore,” according to an article in the New York Times.
Many people take L-carnitine in supplements or in energy drinks. The protein essentially transports fats within mitochondia so they can be burned for energy; acetyl-L-carnitine also contributes to healthy energy production inside brain cells. Because these nutrients have so many benefits, would it really be wise to cease taking them? If vegans and vegetarians don’t have the proper gut bacteria to metabolize carnitine into something harmful, would it even matter if they took carnitine supplements?
As is the case with most novel studies, more questions than answers have been raised. Without a doubt, more research is needed. But rather than wait for an answer that may take years to obtain, there’s another alternative: Eat less red meat.
Hey, it can’t hurt.