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No, meat is not unsafe-nor is L-carnitine.

A recent study published in the journal Nature Medicine associates the amino acid L-carnitine, found in red meat, supplements, and sports supplements, with the risk of heart disease. Here are some examples of what the media said about it:
The Daily Mail (UK): “Red meat nutrient used in weight-loss and muscle-building supplements could cause heart disease”!
The Dallas News: “Put down that steak! (and energy drinks, too); the carnitine in these foods may increase risk of cardiovascular disease”!

Here is the gist of the study:

• a diet high in L-carnitine promotes the growth of certain bacteria that metabolize the amino acid; 

• during that metabolization, an organic compound called trimethylamine-N-oxide (TMAO) is produced in the blood;

• and  this compound increases risk of heart disease.

The study further states that vegetarians and vegans have different gut bacteria, which do not produce a burst of TMAO after consuming L-carnitine.

There is a lot to find fault with in this study.

First, there’s the question of the study participants. Most of the study was done on mice, though there was a human component-a tiny sample of only six people, five meat-eaters and one vegan. That’s right, their conclusion that vegetarians and vegans have different gut bacteria that don’t produce a burst of TMAO after consuming L-carnitine was based on just one individual.

We also don’t know how healthy the five meat-eaters were in this study. The study found that the red meat eaters did not produce TMAO after a course of antibiotics. This suggests that these subjects’ immune systems were already damaged-not that all meat eaters’ are. At the same time, it is still unclear whether TMAO production is caused by eating red meat at all (this was just an assumption), and whether raised TMAO levels actually cause heart disease.