For years it has been thought that consuming too much red meat may increase a person’s risk for heart disease. New research is indicating that it may not be the red meat that is the problem, but the microbes in our guts. High concentrations of the nutrient L-carnitine are found in red meat. L-carnitine helps transport fatty acids into the mitochondria of cells. The mitochondria are the energy powerhouses of cells. Doctor Stanley Hazen the section head of preventive cardiology and a biochemist at the Cleveland clinic in Ohio wondered if L-carnitine could be the link between red meat and heart disease.  From prior research Dr. Hazen knew that when fed to mice the compound trimethylamine N-oxide (TMAO) increased the risk for future heart disease in the mice. TMAO is created when bacteria in the intestine break down some types of food. Dr. Hazen wondered if the same bacteria converted L-carnitine to TMAO thus linking L-Carnitine to heart disease. It is unclear why TMAO seems to link to a future risk of atherosclerosis but one possible explanation is that it makes it easier for immune cells in the arteries to collect cholesterol. (Atherosclerosis is a condition in which the arteries thicken as a result of the build up of cholesterol in cells).

To answer this question Dr. Hazen fed research participates steak and then followed up the meal with a blood test to measure their TMAO levels. After initial tests were done, he put several participants on antibiotics for a week to wipe out their gut flora. He then fed these participants steak and retook their blood tests. What he found was that the participants that took antibiotics had no TMAO in their blood. This shows that the conversion of L-carnitine to TMAO cannot happen when bacteria are not present. These results suggest that microbes in our gut are responsible for the breakdown of L-carnitine to TMAO. So it might not be the steak that is bad for our hearts after all, but the way bacteria in our gut convert L-carnitine to TMAO.