We’ve thought for decades that red meat is unhealthy. Earlier this month we found out why, a neat story involving a molecule called carnitine found in meat, metabolized by the bacteria that live in our gut. The resulting chemical, according to studies in mice, is linked to heart disease. Here is the paper. Open and shut case? That would be nice, but no.

There is a larger and more uncomfortable story here, and I don’t mean the fact that they got a vegan to eat a steak for science. (Although I would love to have heard that conversation.)

Here’s what I mean. The carnitine study was shouted from the rooftops, or the New York Times which is basically the same thing. But two more studies that came out in the following weeks resulted in less-than-triumphant coverage: one agreed with the first study, but opened up the complexity of the metabolic pathway involved. No longer just carnitine and TMAO, this one mentioned lecithin, choline, and betaine.

The other study claimed that carnitine, as a supplement, protects against heart disease. This meta-study looked at outcomes in patients who had already had one heart attack, and were assigned to take carnitine or placebo. The supplement was associated with lower risk of death, angina, and arrhythmia – but not heart attacks themselves, which is already a little weird.

http://blogs.plos.org/publichealth/2013/05/01/do-we-have-something-against-red-meat-or-just-complexity/