A study in the journal Nature Medicine showed that carnitine in red meat was broken down by bacteria in the gut. This kicked off a chain of events that resulted in higher levels of cholesterol and an increased risk of heart disease.
There has been a wealth of studies suggesting that regularly eating red meat may be damaging to health. However, this was not thought to be the whole story.
Experiments on mice and people showed that bacteria in the gut could eat carnitine. Carnitine was broken down into a gas, which was converted in the liver to a chemical called trimethylamine N-oxide (TMAO).
In the study, TMAO was strongly linked with the build-up of fatty deposits in blood vessels, which can lead to heart disease and death.