According to the Centers for Disease Control and Prevention, 715,000 people in the U.S. suffer from a heart attack each year. High blood sugar, smoking and high blood pressure are all known to contribute to the possibility of heart disease and heart attacks.
Eating large quantities of red meat also increases your risk of heart disease because it contains high levels of cholesterol and saturated fat – right? While that may be at least partially true, researchers from Ohio’s Cleveland Clinic say that their new study may have identified the truer culprit. According to their study, the primary component in red meat that influences heart disease risk may be l-carnitine, a nutrient also readily available in dietary supplements. What is l-carnitine, and why are people taking it in supplement form if it increases the risk of developing heart disease?
L-Carnitine: Bad for Mice, Bad for People?
The researchers began their work roughly two years ago, when lead researcher and preventive cardiology specialist Dr. Stanley Hazen and his team made the discovery that intestinal bacteria can convert portions of dietary fat choline into the by-product trimethylamine-N-oxide, or TMAO. In their most recent study, the researchers examined l-carnitine because its chemical structure is very similar to that of choline’s.
Dr. Hazen and his team examined the l-carnitine levels in the blood of almost 2,600 adults, including a fairly even mix of men and women. The researchers found that, in subjects with high levels of TMAO in their blood, the amount of l-carnitine present in the blood was a solid indicator as to whether that person had coronary heart disease, as well as whether he or she would be likely to die of stroke, heart attack or another major cardiovascular event over the next three years.
The researchers also conducted a study on mice, which are genetically similar to humans, to see how l-carnitine affected their cardiovascular risk rates. One group of mice was fed a typical vegetarian diet, while another group received a diet that included an l-carnitine supplement.
The group of mice fed the l-carnitine diet had significantly more TMAO in their blood, and they experienced atherosclerosis at roughly double the rate of the mice in the vegetarian group. Atherosclerosis is the scientific name for hardening of the arteries, which is the top cause of deadly cardiovascular events.
According to Hazen, consuming l-carnitine regularly and in high quantities could increase the risk of heart disease because doing so changes the way the body metabolizes cholesterol. Specifically, less cholesterol is eliminated as waste, and more of it is stored in the artery walls.
A Reason to Cut Back on Red Meat?
In a final component of their study, the researchers compared 23 vegetarians and vegans to 51 individuals who regularly consume meat. They found that people in the vegetarian group had far lower TMAO blood concentrations than people in the meat-eater group.
So, why do people take l-carnitine supplements when it appears to be one of the most unhealthy components of red meat? As a supplement, l-carnitine is usually billed as an energy booster, and can be found in certain “muscle milks” and energy drinks. However, Hazen and his colleagues are unaware of any scientific studies proving that l-carnitine is beneficial as a supplement.
Hazen says that the new study findings are a compelling reason for people to reduce the amount of red meat they consume in their diets, by eating red meat less frequently, in smaller portions, or both. In reality, l-carnitine is difficult to avoid entirely, as it’s found in poultry, fish and various dairy products such as milk. However, the highest concentrations of it are found in red meat.
The Bottom Line
L-carnitine, a nutrient found in red meat and certain dietary supplements and energy drinks, may be one of the primary links between consuming red meat and developing heart disease. The researchers conducted the study after suspecting that cholesterol and saturated fat were not exclusively responsible for the link between red meat and heart disease.
The full text of the study can be found online in Nature Medicine.