Attack of the Killer TMAOs!

Things that make you say, "Hmmm..."

This month the popular press picked up on an April 7, 2013 article published in Nature Medicine  Splashed across the internet were titles like "Culprit in Heart Disease Goes Beyond Meat's Fat (New York Times), and "Researchers Find New Pathway Linking Heart Disease to Carnitine" (Forbes--Forbes later recanted with "Is Red Meat a Fish Story? Why You Should Never Believe Health Headlines", but the article was too little, too late )

In the Nature study, when fed lean red meat and carnitine, vegans and vegetarians were found to have far less TMAO (trimethylamine-N-oxide) in their blood streams than meat eaters.  The authors note TMAO is thought to contribute to heart disease.   Carnitine was also cast under a shadow of suspicion in their study.

In an interesting twist, ten days after the Nature publication, the Mayo Clinic released a meta-analysis (an evaluation of many studies that address the same issue, in this case carnitine)  that concludes, "Compared with placebo or control, L-carnitine is associated with a 27% reduction in all-cause mortality (mortality=death--AC), a 65% reduction in VAs (deadly heart rhythms--AC), and a 40% reduction in anginal symptoms (heart pain--AC) in patients experiencing an acute myocardial infarction (a heart attack--AC)."   In other words, L-Carnitine looks good for the heart.  Sadly, the Mayo study was overshadowed by the fiery press releases on the Nature study. 

Please let me explain how sad this situation is.

My distinguished colleague, Richard D Feinman PhD (for more information, look him up on Wikipedia :), looked into the Nature authors' reference list for the study and found a curious thing.  Among the references in the Nature article is #33, which contains a table describing the overriding problem with the very paper that listed it.  How the Nature authors overlooked this vital information remains a mystery:

Clicking on the table may enlarge it.

If you look at this table you realize that beef is a mini player in the story of TMA/TMAO (TMA is the molecule from which the liver makes TMAO).  Peas promote over twice as much as beef, and halibut promotes a whopping 100+ times as much TMA/TMAO as beef.

Does red meat kill?  No proof to date, and there is evidence to the contrary. Does TMAO (and/or carnitine) kill, or this just a red herring?

We do not have all the answers.  We never do.  If the Nature article hasn't deterred you, my advice: Ignore the media hype and enjoy your beef guilt-free.  But if you believe in Killer TMAOs, according to the table above you should bid farewell to fish. 

As for my dinner plate, surf and turf are still on the menu.