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Avoid Carnitine and Lecithin Supplements

A landmark study in the New England Journal of Medicine shows that choline in eggs, poultry, dairy and fish produces the same toxic TMAO as carnitine in red meat, which may help explain plant-based protection from heart disease.

Earlier this year, a research team at the Cleveland Clinic offered another explanation as to why meat intake may be related to mortality (see, for example, Harvard’s Meat and Mortality Studies). They noted that “Numerous studies have suggested a decrease in atherosclerotic disease risk  (our  number 1 killer) in vegan and vegetarian individuals compared to omnivores,” but reduced intake of dietary cholesterol and saturated fat may not the full story.  The researchers found that within 24 hours of carnitine consumption—eating a sirloin steak, taking a carnitine supplement—certain gut bacteria metabolize the carnitine to a toxic substance called trimethylamine, which then gets oxidized in our liver to TMAO, trimethylamine-n-oxide, which then circulates throughout our bloodstream. There’s a diagram in the above video.

The way we know it’s the gut bacteria is that if you give people antibiotics to wipe out their friendly flora, you can apparently eat all the steak you want without making any TMAO, but then if you wait a couple weeks until your gut bacteria grows back, you’re back to the same problem.

What’s so bad about this TMAO stuff? It appears to increase the buildup of cholesterol in the inflammatory cells in the atherosclerotic plaques in our arteries, increasing our risk of heart attack, stroke, and death. The role of these inflammatory “foam” cells (so-called because they’re so packed with cholesterol they look foamy under a microscope) is explained in my video series that starts with Arterial Acne and Blocking the First Step of Heart Disease.

What does carnitine do? It’s involved in energy production in the mitochondria (“power plants”) in our cells. The enzyme that uses carnitine to help us burn fat, carnitine palmitoyl transferase, is actually upregulated by about 60 percent in those eating meat-free diets, which may help explain why those eating plant-based diets tend to be slimmer. More details in my video How to Upregulate Metabolism.

How do you stay away from carnitine? Well there’s zero dietary requirement; our body normally makes all that we need. The problem is that the bodies of other animals also make all that they need so when we eat them, their carnitine can end up in our gut for those bacteria to feast upon, resulting in TMAO.

Some animals make more carnitine than others. Carnitine is concentrated in red meat, and so this new body of research has led to recommendations to decrease red meat consumption as well as avoid carnitine-containing supplements and energy drinks.

What most media reports missed, though, is that gut bacteria can turn the choline found in eggs, poultry, fish, dairy, and lecithin supplements into TMAO too. So it’s not just a problem with red meat. The good news is that this may mean a new approach to prevent or treat heart disease: “The most obvious is to limit dietary choline intake.” But if that just means decreasing egg, meat and dairy consumption, the “new” approach sounds just like the old approach.

Unlike carnitine, we do need to take in some choline, so should vegans be worried about the modest amounts of choline they’re getting from beans, veggies, grains, and fruit? And same question with carnitine. There’s a small amount of carnitine found in fruits, veggies, and grains as well. Of course it’s not the carnitine itself we’re worried about, but the toxic TMAO, and you can feed a vegan a steak without getting a TMAO spike. Literally. The researchers convinced a long-time vegan to eat an 8-ounce sirloin, in the name of science. The vegan got the whopping carnitine load, but hardly any TMAO was produced. Apparently, the vegans don’t develop those TMAO-producing bacteria in their gut, and why would they?

It’s like the whole prebiotic story I detail in videos like Boosting Good Bacteria in the Colon Without Probiotics. When we eat a lot of fiber, we select for fiber-munching bacteria, and some of the compounds they make with fiber are beneficial, like the propionate that appears to have an anti-obesity effect I explored in Fawning Over Flora. It seems that if we eat a lot of animal products we may instead be selecting for animal-munching bacteria, and some of those waste products—like the trimethylamine—may be harmful.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos here and watch my full 2012-2013 year-in-review presentation Uprooting the Leading Causes of Death.

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Dr. Michael Greger

A founding member of the American College of Lifestyle Medicine, Michael Greger, M.D., is a physician, author, and internationally recognized speaker on nutrition, food safety, and public health issues. Currently Dr. Greger serves as the Director of Public Health and Animal Agriculture at The Humane Society of the United States. Hundreds of his nutrition videos are freely available at


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7:46AM PDT on Aug 31, 2013

Chris Kresser L.Ac has also weighed in on this issue,9 comparing the hypothesis that red meat causes heart disease via TMAO to the patently false notion that dietary cholesterol and saturated fat cause heart disease by raising serum cholesterol. Kresser lists three reasons for not taking the featured study at face value:

Inconsistent epidemiological evidence
“Healthy user” bias, and
Inconclusive and insufficient evidence on the role of TMAO in heart disease
“...even if Paleo meat eaters have higher TMAO levels than vegans and vegetarians, we still don’t have evidence proving a causal relationship between TMAO and cardiovascular disease,” he writes. “Once again, the supposed link between cholesterol and saturated fat and heart disease should serve as a reminder not to jump to hasty conclusions that unnecessarily deprive people of nutrient-dense, healthy foods. It is virtually impossible to control for all of the possible confounding factors.”

7:44AM PDT on Aug 31, 2013

He points out that red meat is only one of many foods that increases TMAO when eaten, and cites data from a 1999 study that evaluated TMAO excretion following consumption of 46 different foods, which shows that red meat generated no more TMAO than fruits and vegetables. In fact, some veggies, such as peas, cauliflower and carrots generated more TMAO than beef did! Still, none of the foods generated TMAO at levels that were statistically different from the control. (Similarly, there was no statistically significant difference between different kinds of meats, compared to the control.)

2:03AM PDT on Jul 12, 2013

Thank you :)

10:29AM PDT on Jul 10, 2013

Much to consider...
Thank you for good info.

2:59PM PDT on Jul 1, 2013


6:11PM PDT on Jun 26, 2013

Just great! & hear I thought eating organic eggs were ok, even good for me! I am more confused than ever! Also lecithin I have been told for yrs is GOOD to supplement w/! WTH!

6:15PM PDT on Jun 22, 2013

Thanks - That was forwarded to all the boys ....

11:04AM PDT on Jun 22, 2013

I have had genetic damage from toxic chemicals, on the job, 20+ years ago, and I NEED carnitine supplements, not every body is the same.... =)

5:11AM PDT on Jun 22, 2013


12:55AM PDT on Jun 22, 2013

most of my aunts and uncles lived into their 90's, they all ate meat and dairy as well as veggies and fruits (though most of it they grew themselves until they were quite old) and none of them had problems with cholesterol or plaque in their arteries. They took no supplements either, got all their nutrition from food. Maybe they didn't have a problem with it because they were always physically active. I think we need to take the genetic component in mind, rather than a possibly flawed study. My dad was healthy and didn't supplement with carnitine or lecithin, so neither
will I.

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