Wednesday, April 17, 2013

Carnitine: Another Scapegoat?

Dr. Hazen and his colleagues at the Department of Cellular & Molecular Medicine, Cleveland Clinic linked carnitine for red meat to high levels of trimethylamine-N-oxide (TMAO) to heart disease. Days later on April 12, a review of several randomized control trials on carnitine was published in the Mayo Clinic Proceedings. Overwhelmingly, carnitine was found to ameliorate the symptoms of heart disease and peripheral artery disease, and to lead to a significant reduction ventricular arrhythmias and anginal attacks following a heart attack, compared with placebo or control.

Every muscle, including the heart, needs fat for energy and carnitine,  a quaternary ammonium, helps to shuffle fatty acids across the mitochondrial wall, thereby increasing the rate in which they are available to the skeletal or heart muscle. Carnitine thus increases endurance and energy levels for aerobic activity, which uses fat for fuel, and the rate of burning fat. Some studies have shown that carnitine can reduce symptoms of angina, heart failure and peripheral artery disease. Carnitine is present in high levels in many sports drinks, so Hazen's article is also of concern to those who consume them, whether they eat red meat or not.

In Hazen's study, chief of cellular and molecular medicine at the Cleveland Clinic’s Lerner Research Institute, Stanley Hazen, tested the carnitine and TMAO levels of 2,595 patients who were omnivores, vegans and vegetarians. In patients with high TMAO levels, the more carnitine in their blood, the more likely they were to develop cardiovascular disease, heart attacks, stroke and death. The higher TMAO levels were due to the metabolism of carnitine by certain gut bacteria. In 2011, Hazen had shown that TMAO is connected to high levels of cholesterol. Mice bred for artherosclerosis had high levels of TMAO, but not if they were cleared of gut bacteria that metabolize certain molecules to TMAO.

The study had several flaws. The authors claimed that the base levels of TMAO were higher in 30 omnivires than 23 herbivores. They assumed that red meat, more than any other type of food, and high TMAO levels are correlated; TMAO is linked to cholesterol and thus artherosclerosis. The cooking methods for the meat may have led to nitrosamines that are precursors of TMAO. The authors did not control for the effects of antibiotics in meat on the levels of certain gut bacteria that increase TMAO levels. The authors did not write about TMAO being the byproduct of carnitine if legumes or other non-meat sources of carnitine are ingested. A study could be done to find this out. The authors did not publish which gut bacteria increase levels of TMAO. Also, some gut bacteria reduce it, so the problem may be in the type of gut bacteria a person has (or the way meat is prepared or the antibiotics it contains), rather than in eating carnitine. For the animal part of the experiment, mouse and human gut bacteria are not alike.

A recent article in the New York Times highlighted the growing concern about pseudo-journals and pseudo-conferences, where scientists pay to have their studies published or to attend. Contrary to what some may believe, many scientists fall prey to the same ego concerns that, let’s say, actors may have: They want to get their name out there, win rewards – in their cases, grants, and move ahead of their colleagues.Perhaps more rigor and less sensationalism are needed in the study design of scientific articles, and more refrain is needed in declaring and supporting claims that are not sufficiently supported.

Last but not least, nothing can take the place of finding the right diet and exercise program for you. Everyone’s body is different. Balance is key in nutrition. Scapegoating or cutting out one food source is just another quick fix. Find what your body needs, get your nutrients, keep informed by reading a variety of articles about each food source, and use your body – move!

My book Pocket Guide to Fitness is available on and If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories. These two books are on my Web site and like, if you so see fit, my book page at

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