The Red Meat Controversy: It's Not the Meat, It's the Carnitine
I think researchers might just have it out for red meat. And for some reason they are pro-alcohol. You see studies every year about how bad red meat is for you and how good alcohol is for you in moderation. Eggs are another great example, with studies alternating between good and bad each year. It goes to show the effects of the media and popular opinion on research, and this week is no exception. A study performed by the Cleveland Clinic showing red meat is bad for you got national attention in an article by the New York Times.
I’ve always just waved off reports of red meat being linked to heart disease as a matter of fact. Sure if you eat a lot of bad food, including fatty, poorly-raised red meats you’re going to get sick at some point. That’s not advanced science, that’s just common sense. The big difference in this study is the link between lean red meat and heart disease. That’s right, even the non-fatty stuff that most of us think is fine - especially the paleo diet followers among us.
But wait, all this talk from researchers about red meat seems to just be an attempt at media attention. And it worked, because sure enough the Times picked up the story. What the research actually found was a link between the amino acid L-carnitine and heart disease. Red meat just so happens to be high in carnitine. If true, however, carnitine supplements, carnitine containing drinks, and really anything with carnitine could be an issue as well.
While the media didn’t give this point a ton of attention, for readers of Breaking Muscle, it might be much more important. I don’t know about you, but I love my red meat, and I have a bottle of carnitine caps close at hand as well. Carnitine is a required component of the fat-burning process in the body, so it is very important, and many athletes take it as a performance enhancer or contributor to weight loss.
Apparently, carnitine is metabolized by intestinal bacteria into a chemical called TMAO. TMAO alters cholesterol transport and metabolism, and voila, heart disease over time. Indeed the researchers used antibiotics and a vegan participant to test the theory, and in both cases the TMAO levels remained low, even with consumption of high dietary carnitine. This is because in both cases the microflora of the intestine didn’t exist to create the TMAO.
So does this mean red meat is out? Let’s not be so hasty. With red meat consumption having a long precedent in human history, we should be very demanding of any research indicating it isn’t healthy for us. I’m not sure this fits the bill.
We might still have a selection bias here. Just because carnitine metoblizes into TMAO doesn’t automatically mean it is bad for you. Carnitine is required for human life, and the human part of the study focused on meat consumption. It could simply be that the vegetarian participants led a healthier (non-average) life. However, mice supplementing with carnitine did also exhibit greater risk for heart disease. Happily, researchers found that circulating carnitine only correlated with heart disease if TMAO was also present. As such, it seems likely that high carnitine intake might not be an issue if it is utilized rather than metabolized.
I do love a good steak, and I’m not convinced it is bad for you. I think more research is needed on the variables before we just oust the red meat from our diets, but I’m going to keep an open mind on this one.
1. Robert Koeth, et. al., “Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis,’ Nature Medicine (2013).
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