Does L-Carnitine Really Cause Heart Disease?

Maylin Rodriguez-Paez, RN

We’ve been around long enough to know the media takes just about every opportunity to put
supplements in a negative light. And rarely do they present an objective picture of reality.

This is why the latest headlines linking carnitine to heart disease didn’t surprise us at all.

In a study conducted by the Cleveland Clinic, researchers sought to examine a link between red meat consumption and heart disease, placing L-carnitine as the middleman.

The media, however, failed to address both the study’s flaws and L-carnitine’s impressive track record.

Below, we’ll explore the details of the study and provide actual evidence of L-carnitine’s heart supportive effects.

The Details of the Carnitine Study

Scientists have long-wondered why high intakes of red meat have been associated with heart disease. Researchers at the Cleveland Clinic think TMAO (trimethylamine N-oxide) and carnitine are to blame.

Red meat is a rich source of carnitine, and during digestion, bacteria convert it into TMAO. For the study, Cleveland researchers examined TMAO and carnitine blood levels of heart patients, omnivores, vegans, and vegetarians.

They also took mice and fed them carnitine-rich diets, with one group receiving antibiotics to suppress their gut bacteria. Here’s what they found:

  • Following the ingestion of carnitine, omnivores had higher TMAO levels than vegans and vegetarians. The researchers attributed this to differences in gut bacteria.
  • Vegans and vegetarians didn’t produce significant amounts of TMAO even after ingesting large amounts of carnitine.
  • Heart patients with increased carnitine levels had an increased risk for cardiac disease and heart attacks, but only when they had higher levels of TMAO.
  • The mice had increased levels of atherosclerosis, but those given antibiotics did not demonstrate these changes.1
Based on their results, the researchers thought they had enough evidence to link carnitine to heart disease. However, we see a very different story.

Flaws of the Carnitine Study

Basically, there are two main flaws with the study. The first (and it’s a big one) is focusing on TMAO as a cardiac risk factor.

There is very little evidence linking TMAO to heart disease. In fact, only three studies exist regarding this issue. In addition, TMAO is not an accepted cardiac risk factor in the scientific community. Here’s what a Harvard researcher said about the Cleveland study:2

“TMAO needs to be studied more in humans to understand the implications for public health…This new research is very interesting but is not yet the final word.”

The second issue found with the Cleveland study is the focus on carnitine. The study clearly shows that gut bacteria are what truly made the difference in TMAO levels. The main reason the vegans and vegetarians didn’t make significant amounts of TMAO was due to differences in gut bacteria. Even the Cleveland researchers recognize this:

“Intestinal microbiota may thus contribute to the well-established link between high levels of red meat consumption and CVD risk.”

Also, it’s important to note that certain strains of gut bacteria have been linked to different diseases. One in particular is Streptococcus bovis.

This “bug” has been linked to all sorts of health problems, including endocarditis11,12 Unfortunately, for us it’s also found in pre-packaged red meat.

This link hasn’t been explored much, but we think it deserves a lot more attention. Don’t you?

Carnitine – The Real Story:

When the media splashed its sensational headlines linking carnitine with heart disease, they forgot to mention one crucial detail — carnitine is perhaps one of the most important nutrients for your heart.

Carnitine transports fat to the mitochondria of your heart cells, where it’s “burned” for energy. Unlike other organs, your heart runs mostly on fat.3

Without carnitine, your heart’s fuel supply is compromised. And just like a car, your heart can’t run without fuel. That’s why there is plenty of evidence showing that carnitine improves heart health, not harms it.

In studies, carnitine has been shown to improve the following measures associated with heart health:

  • Improve blood lipids4
  • Lower blood pressure4
  • Improved heart rate4
  • Decrease death rates in heart attack survivors4
  • Increase blood flow to the heart5
  • Relieve symptoms of congestive heart failure6
  • Decrease angina (chest pain)7
  • Slow the progression of atherosclerosis8
  • Increase exercise tolerance in patients with heart and vascular diseases9

The Bottom Line

With all of these positive effects in mind, we’re pretty confident in carnitine’s ability to promote heart health. The evidence is just too strong to suggest otherwise.

Look at it this way — there are many studies showing that smoking is bad for you, but if a few came out showing a benefit, would you start smoking? Well, the very same logic can easily be applied here.

This one study by the Cleveland Clinic isn’t changing our minds. Will it change yours?


  1. Nat Med. 2013 Apr 7. doi: 10.1038/nm.3145.
  2. Available at: Accessed April 14th 2013.
  3. Herz. Feb 1987;12(1):41-50.
  4. Drugs Exp Clin Res. 1992;18(8):355-65.
  5. Arterioscler Thromb Vasc Biol. 2010 Mar;30(3):426-35.
  6. Jpn Circ J. 1992 Jan;56(1):86-94.
  7. Int J Clin Pharmacol Ther Toxicol. 1985 Oct;23(10):569-72.
  8. Atherosclerosis. 1995 Apr 7;114(1):29-44.
  9. Br J Nutr. 2009 Oct;102(8):1145-53.
  10. Appl Environ Microbiol. 1993 Mar;59(3):936-8.
  11. Cancer Epidemiol Biomarkers Prev. 2008 Nov;17(11):2970-9.
  12. Eur Heart J. 1995 Dec;16(12):1975-80.


Stephen Knows Cancer said...

There seems to be a lot of research being done on red meat and its affects with heart disease. However, I believed that there had been a number of issues with these studies. I am really glad to see that you were willing to delve a little further into this subject, and presents some facts that the media may have missed.

Anonymous said...

As a precaution, I've cut back on beef consumption, and I continue to supplement with acetyl-L-carnitine (but not L-carnitine, which I was not supplementing previously.) I haven't yet found any mentions of studies implicating ALC in atherosclerosis. If TMAO really is a significant risk factor, I'm hoping that the gut bacteria do not convert ALC to TMAO. Note, one supplement I do take is bromelain. In the early 1970s, it was shown to reduce plaque thickness in rabbit models of atherosclerosis. Bromelain being a natural substance, not a drug, the Big Bucks crowd swept it under the carpet. Yet, it works for myself and others, reducing symptoms consistently, from what I have seen.

LifeExtension said...

Anonymous - Thanks for chiming in! Overall, the research is weak linking carnitine to heart disease, so we wouldn't worry about it. If anything, you're better off taking it. Now, if you'd like to step up your heart health, we suggest you take a look at this link. It provides additional suggestions:

Jenni said...

Information is so valuable but can be damaging if not presented with all of the correct facts. This is why no one can agree on what is healthy or not. There are too many studies with giant holes in the implementation. Thanks for spreading the awareness. So much misinformation can cause severe health problems.

LifeExtension said...

Jenni - Agreed! Thanks so much for taking the time to chime in.

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LifeExtension said...

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Chris Kavanagh said...

You're right, this B.S. study is no surprise. Often studies done on supplements are designed to fail, and this appears to be one. Big Pharma can't have the TRUTH coming out and slowing their BILLIONS in drug sales, now can they.

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