Latest Meat Scare: ‘Shocking Ignorance’
The meat-will-kill-you brigade was out in full force last week. This time, the media frenzy and exaggerated headlines were the result of research being published in the journal Nature Medicine.
Translation: When gut bacteria process L-carnitine, which is found in red meat, it leads to hardening of the arteries.
Based on that title and the claims made in the article, perhaps extreme headlines are justified?
Well, let’s take a look at the headlines, the basic premise, and how some thought leaders have interpreted the research. Hopefully, this article will provide you with some insights and the proper starting point for you to continue to looking into the issue if you wish. Even if the Internet is robbing you of our ability to focus, it’s worth following along just to cut through this round of BS and in order to better recognize the next round, which is sure to come.
Before we commence, the proper music is in order. Let’s set the stage, shall we? Hit play.
Here’s how the media grabs the eyeballs and clicks that they so desperately need.
- New York Times: Culprit in Heart Disease Goes Beyond Meat’s Fat
- Wall Street Journal: New Health Worry in Red Meat
- TIME: It’s Not Just the Fat: There’s Another Way Red Meat May Harm the Heart
- Wired: Red Meat May Cause Heart Disease by Disrupting Gut Bacteria
- CBS News: Carnitine chemical, not fat, may explain link between red meat and heart disease
- LA Times: Red meat and heart disease link: Not all about the fat?
Want some more? OK, as long as those headlines haven’t raised your stress levels and blood pressure too high, there are plenty more to go around:
- Washington Post: Fat and cholesterol aren’t only heart dangers of red meat
- NBC News: Red meat linked to heart disease
- Dallas Morning News Health Blog: Put down that steak! (and energy drinks, too); the carnitine in these foods may increase risk of cardiovascular disease
- BBC: Red meat chemical ‘damages heart’
- Business Insider (Science): Researchers Have Found What Makes Steak Unhealthy
Sadly, I could go on, but let’s call it done. Clearly, red meat is going to kill you and you shouldn’t be eating it, because now scientists finally KNOW WHY it is KILLING you. They’ve certainly been looking for a reason long enough.
The Simple Version
Here’s the basic story:
Meat contains a compound called carnitine. When we eat meat, the bacteria in our digestive system processes the carnitine and generates another compound called trimethylamine (TMA). The liver then converts the TMA into trimethylamine n-oxide (TMAO). The current research claims that higher blood levels of TMAO will lead to atherosclerosis.
Simple right? Either it does or it doesn’t.
Well, no. And when you take a look at the research methods, the confounders, the potential conflict of interest, and other factors that stack up against this conclusion, you begin to see that it’s anything but simple. Not only that, the researchers’ conclusions seem far from likely.
The Rest of the Story
Anthony Colpo provides an entertaining, yet thorough and scientific, tear-down of the study. If you’re going to read about TMAOs and carnitine, you may as well have a good time and start with Bullshit Study of the Year: “Carnitine Causes Heart Disease”.
Colpo minces no words and tells us plainly:
- Carnitine does NOT cause heart disease.
- No-one — I repeat NO-ONE — has ever shown red meat nor supplemental carnitine to cause heart disease in human beings. Not the ‘researchers’ responsible for the appalling Nature Medicine paper, and not anyone else.
Other salient points include:
- This study is not a randomized controlled trial (RCT), and it also relies on other non-RCT research:
- The researchers accurately state that when we eat red meat, the carnitine in that meat is converted to TMA by our gut microbes. But the researchers go on to claim this new TMA causes heart disease by promoting the uptake of cholesterol into the artery walls.
- As carnitine levels rose in test subjects, so did patients’ age, rate of smoking, and pre-existing heart conditions
- The researchers used specially bred mice that “spontaneously develop ‘atherosclerotic lesions’ on a standard chow diet.”
- (Heart-healthy) fish causes the greatest increase in TMA levels.
- Carnitine is found in every cell of the body and plays a critical role in energy production
So what we have is a study which used misrepresented epidemiology, blatant cherry-picking and a singles bar attitude to metabolomics as a springboard to validate what strongly looks like a preconceived agenda to implicate red meat and carnitine in the pathogenesis of heart disease.
Colpo also points to Spanish, Egyptian and Italian research that the study in question here apparently ignores. They show potential improvements related to cardiovascular deaths, heart rhythm, reduction of angina attacks, blood pressure, and even erectile dysfunction.
Check out the article for a look at the competing financial interestes of the research authors as well as the rest of the general awesomeness therein contained.
In Paul Jaminet’s Lessons from the Latest Red Meat Scare, he quickly informs us that the same group behind the current study was behind a similar study just a couple of years ago. In their previous study, phosphatidylcholine was shown to be metabolized by gut flora, which then lead to TMAO production in the liver. Sounds familiar, right? And, phosphatidylcholine (or PC or lecithin) is found in eggs, milk, liver, red meat, poultry, shell fish and fish.
This doesn’t inherently invalidate their current research, but it’s interesting to know that they’ve been on the TMAO case for quite some time.
In the remainder of Jaminet’s assessment, we learn:
- His book asserts that high protein intake is suboptimal for gut health
- Gut bacteria can ferment protein, which generates toxic compounds
- He boils down gist of the new research to: “fermentation of meat in the gut produces TMA leading to TMAO production which may increase your chance of atherosclerosis by 11%”
- The risk is highly dependent on the nature of an individual’s gut flora
- A low fiber diet could lead to starving the “good” bacteria and feeding the “bad” bacteria that produce TMA
- TMAO in blood only becomes atherosclerotic in the context of metabolic syndrome brought on by endotoxemia
- A high-sugar, high-flour, low-fiber diet provides the necessary landscape for endotoxemia
- Fiber and resistant starches from in-ground starches (like potatoes) are protective
- Eating excessive meat provides more protein for potential fermentation, which then can produce harmful byproduct
Paul’s full article is here.
If you are not familiar with Chris’ work, he is well known with regards to his work on cholesterol.
- 8 oz. of carnitine-rich foods, like meat, produce no more TMAO than fruits and vegetables, while seafood produces significantly more
- In other studies, beef and other foods, did not produce significantly more urinary secretion of TMA + TMAO than a control meal
- Fruits and vegetables produced similar results to beef (red meat)
- Chicken and other meats produced similar results to beef (red meat)
- Several foods produced higher values than beef (like mushrooms, peas, eggs, and seafood), so why pick on red meat?
- There could potentially be gender differences in TMAO production
- The post-meal increases in TMAO levels, relative to the total TMAO pool, appear to be insignificant
- It is unknown whether any outliers in the research group drastically altered the average results
- Female C56BL/6J mice genetically engineered to be missing ApoE, an important protein involved in lipoprotein metabolism, developed twice as much atherosclerosis when fed a thousand steaks a day worth of carnitine.
- If carnitine conversion to TMAO causes atheroscelrosis, then seafood ought to be considered the main culprit — yet Kitavans, an island people who eat seafood plentifully, are virtually free of heart disease.
In Does Red Meat Clog Your Arteries After All, Mark Sisson provides an easily understood interpretation of the data and offers advice that is equally easily digested, even by those without advanced degrees in biochemistry.
This is probably the article you want to forward along to your Aunt Thelma or Uncle Jack who is worried about your caveman diet, since the others require a bit more geekiness to grok…so to speak.
You can find more about this topic in these articles:
- Chris Kresser — Red Meat and TMAO: Cause for Concern, or Another Red Herring?
- Dr. Stephen DeFelice, M.D. — Carnitine: A Highly Promising Biomarker and Proven Treatment for Cardiac Disease and a Case against It as a Cause of Atherosclerosis
- Andrew Kim — What I Learned from the Red-Meat-Carnitine Study
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What do you think about the latest meat-will-kill-you scare? Sound off in the comments, and please feel free to add additional resources or contrary points of view.