Researchers Have Found What Makes Steak Unhealthy

Researchers have found the compound in red meat that's linked to cardiovascular diseases — like heart attacks and strokes from the buildup of plaques in blood vessels.

Surprisingly, it wasn't the high saturated fat or cholesterol content in the meat, but a different compound called L-carnitine.

But, knowing this could help make steak healthier in the future and provide better treatments for cardiovascuar disease, though a few servings of steak a week is still ok, risk wise.

"There's no need to change our dietary recommendations from this — a Mediterranean style diet with modest meat, fish, dairy and alcohol intake, coupled with more pulses, vegetables fruits, whole grains and mono-unsaturated fats, remains the nutritional blueprint for a healthy and healthful life," Catherine Collins, a dietitian who didn't perform the study, said in a statement from the Science Media Centre.

The culprit, L-carnitine, is sometimes taken as a nutritional supplement, which may be unwise for meat eaters, the researchers said.

In the study, the researchers found an association between how much L-carnitine people take in from meat and their risk of cardiovascular disease. They also saw a direct link between the nutrient and plaque build up in the blood vessels of lab mice.

Interestingly, they found that the effects of this nutrient aren't direct, but seem to be mediated by how it's metabolized by gut bacteria. In the gut, the L-carnitine is metabolized into a compound called Trimethylamine N-oxide (TMAO).

Meat-eaters had more TMAO in their blood and were at a higher risk for cardiovascular diseases.

Studies have found that people who don't eat as much meat don't metabolize L-carnitine as well, but those who eat a lot of it have tons of the bacteria that turn it into TMAO. These gut bacteria are what make red meat dangerous, it seems.

There's a good side to this, though. It indicates that the negative effects of meat-eating aren't linked to the levels of saturated fat and cholesterol in red meat. Maybe one day we could make meat and other sources of L-carnitine in our diet safer to eat by developing a way to block the metabolism of this nutrient in the gut — thereby lowering the risk of cardiovascular diseases.

They also noted that meat eaters could be given a type of antibiotics to kill off these L-carnitine-metabolizing bacteria didn't accumulate as high levels of TMAO in their blood, though we wouldn't recommend taking antibacterials just so you can go on a steak binge.

The researchers note that L-carnitine is used as a dietary supplement by some to ward off cognitive decline or improve fat metabolism. For meat-eaters who have a lot of gut bacteria to turn it into TMAO, that could be dangerous, though the safety of this hasn't been studied.

"But I would strongly recommend that unless you're a vegetarian or vegan, there is a potential risk from taking L-carnitine," Collins said. "If the evidence is confirmed these supplements would do more to damage arteries than provide health benefits."

The new study was published Sunday, April 7, in the journal Nature Medicine.