Hazen and his research team suspected there must be something else in red meat, besides its cholesterol and saturated fat, that explains its association with heart disease. "This study suggests carnitine may be a piece of this link," he said.
The findings were published online in the journal Nature Medicine.
A carnitine connection Two years ago, Hazen and his research team discovered that microorganisms in the intestines can convert substances found in choline, a common dietary fat, to a by-product known as TMAO, trimethylamine-N-oxide.
This new study looked at l-carnitine, which has a similar chemical structure to choline.
Carnitine is a nutrient found at high levels in red meat, but fish, poultry, milk and other dairy products are also good food sources of it. Carnitine is also a popular over-the-counter diet supplement, often billed as helping to boost energy and bulk up muscle. It's found in some energy drinks and muscle milks.
The researchers looked at fasting levelsof blood carnitine in nearly 2,600 men and women. The findings showed that carnitine levels could quite strongly predict participant's risk of existing coronary artery disease, as well as the risk of having a major cardiac event, such as heart attack, stroke, or death over a three-year period, but only in adults who had high blood levels of TMAO.