Nature Medicine has the coolest stuff! This paper was written up by Gina Kolata in Sunday’s New York Times. Koeth et al from the Cleveland Clinic determined a link between a chemical called TMAO (trimethylamine-N-oxide) and heart attacks. They propose a biochemical pathway for TMAO creation that starts with carnitine, an amine found commonly in red meat (and energy drinks…), and gut microbiota metabolizes carnitine into TMAO. Their controls included having vegetarians and vegans (humans and mice) eat meat and measuring TMAO creation. Their TMAO levels did not change after eating carnitine, though the omnivores’ levels did. Another control was to give omnivore mice antibiotics that wiped out their gut microbiomes. TMAO levels didn’t increase in these mice either, showing that the gut microorganisms were responsible for the TMAO. This could be an explanation for why people eating a diet with lots of red meat may get more heart attacks, it’s not the meat itself, but the gut fauna that they cultivate and the TMAO it creates when meat is eaten.