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Apr 7, 2013 06:57 PM

Gut bacteria eating red meat carnitine may be cause of heart disease
"Red meat chemical 'damages heart', say US scientists"

The proposed mechanism is that gut bacteria feeds on carnitine, producing a gas which is broken down in the liver into TMAO ( trimethylamine N-oxide). That in turn is linked to fatty deposits in the arteries.
has been updated to reference this study.

Quantity of carnitine per 100g
Beef steak - 95 mg
Ground beef - 94 mg
Pork - 27.7 mg
Bacon - 23.3 mg
Tempeh - 19.5 mg
Cod fish - 5.6 mg
Chicken breast - 3.9 mg

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  1. There is no one mechanism of heart disease. Consider all the risk factors that are well established. This TMAO stuff is much flimsier than any of them.

    3 Replies
    1. re: sal_acid

      The red-meat risk factor seems to be well established, but apparently the mechanism is not all that clear. This is seen as an answer to that mechanism question.

      1. re: sal_acid

        I've read the original papers and found that the study designs were unusually rigorous and the results clear and compelling.

        I am wondering about the basis for your statement that "this TMAO stuff is much flimsier than any of them."

        1. re: Just Visiting

          The study design was pretty clever - feed vegans and carnivores beef, note different levels of TMAO produced; carpet-bomb their gut bacteria with antibiotics, repeat the experiment, note similar levels of TMAO produced. Even with the tiny study size (2 vegetarians, 5 carnivores), that's pretty compelling.

          So they showed that carnivore's intestinal flora turn carnitine into TMAO; and they suggest that TMAO contributes to, or is at least correlated with, heart disease.

          What they don't explore (kind of tellingly, I think) is whether there are any other sources of TMAO. If it comes only or primarily from the processing of carnitine in carnivores, that's pretty damning for red meat.

          But it doesn't. According to a 1999 study in which 46 different foods and supplements were analyzed to determine their effects on TMAO levels, beef *does* raise TMAO levels (as measured by TMAO in the urine 8 hours after consumption). Chicken, pineapples, and soybeans raise it about the same amount. Peas, carrots and mushrooms raise it significantly more.

          And the absolute worst offender - no contest, not even close - is seafood. A serving of halibut raises TMAO levels more than a *hundred* times as much as a serving of beef does. Other finned fish and shellfish aren't as bad - only 600-800 times more TMAO than beef.

          Examining how beef contributes to TMAO-caused heart disease is like examining how second-hand smoke from the next apartment affects contributes to the lung cancer risk of a three-pack-a-day smoker. It's probably *measurable*, but is it *relevant*?

          (The 1999 study is cited here: - the link to the full study is broken - it's available here: but costs money...)

      2. fuller summary at ScienceDaily

        It's interesting that they found a difference in gut bacteria between meat eaters and vegetarians, and this might affect health.

        The difference in gut bacteria comes up in the discussions about grain fed v. grass fed beef. Maybe it's not the cow's gut that matters but our own. :)

        1 Reply
        1. re: paulj

          I'm curious about how a dog or cat would process the cartinine. Their gut bacteria must be different from ours. Although I haven't read much about canine cholesterol.

        2. And here is the Latest on Nature from Orac at ScienceBlogs:

          1 Reply
          1. re: GH1618

            Speaking Orac, I noticed that carnitine is being sold as a supplement.

          2. Does anybody know what the difference is between the carnitine in the study and acetyl-L carnitine, which is sold as an anti-aging antioxidant?

            1 Reply