L-Carnitine

Supplements and energy drinks that contain l-carnitine claim to be metabolism boosters that can help you shed weight and increase your athletic performance. However, no scientific data backs up these claims. In fact, taking l-carnitine can make you may lose your good health rather than extra pounds. Read on to find out why.

A Meaty Subject

The word carnitine comes from the Latin word for flesh: carnis, which is also the root of the word carnivore. Your liver and kidneys make carnitine from two amino acids, lysine and methionine. Carnitine is stored in your skeletal muscles, brain, and heart. In men, carnitine is also stored in sperm.

This compound plays an important role in your body, escorting long-chain fatty acids to your cells’ mitochondria, where they produce energy. Carnitine also ushers toxic byproducts of energy production out of your cells, so they don’t build up.

The National Institutes of Health (NIH) says that healthy adults and children don’t need to take carnitine supplements. The Institute of Medicine lists no recommended dietary allowance of carnitine. Your body makes quite enough, thank you very much.

Food Sources

Carnitine is also found in food, mostly in red meat. A 4-ounce steak contains between 56 and 162 grams. A 4-ounce hamburger delivers between 87 and 99 grams of carnitine. The redder the meat, the higher its carnitine concentration. Smaller amounts of carnitine are also present in fish, poultry, and dairy products.

Something’s Fishy

There is no scientific data to support the bloated claims about l-carnitine’s fat-burning capacity, or its mythical ability to spur peak athletic performance.

On the contrary, l-carnitine supplements have potential side effects such as nausea and vomiting, cramps, and diarrhea. Carnitine supplements can even wreck your social life, because taking 3 grams a day can produce a fishy body odor.

People with kidney disease or seizure disorders should exercise particular caution with carnitine supplements or energy drinks that contain it, like Monster Energy or 5-hour Energy. That’s because carnitine can cause muscle weakness in people with kidney disease, and seizures in people who have a seizure disorder.

The Carnitine Clog

The most serious complication associated with carnitine is its link to an elevated risk of heart disease. Cleveland Clinic researchers found that a metabolite of carnitine drives up your chances of developing atherosclerosis, or hardening of the arteries.

Carnitine itself isn’t the problem. It’s what happens when carnitine meets the bacteria in your intestines. When you tuck into a steak or swallow an l-carnitine capsule, the bacteria in your gut produce a chemical called trimethyl amine. Then your liver converts trimethyl amine into trimethylamine N-oxide, or TMAO. This byproduct gums up your arteries.

Possible Reasons to Go Meatless

Non-meat-eaters appear to have different gut bacteria, and don’t experience the same TMAO spike if they do eat meat or take an l-carnitine pill. Researchers still don’t know which gut bacteria trigger TMAO production after eating meat or taking l-carnitine. Further studies to identify these bacteria will reveal more about the interchange between what we eat, our intestinal flora, and the potential to develop cardiovascular disease.   

Dr. Oz Says “Oops”

The evidence about l-carnitine, TMAO, and heart disease prompted Mehmet Oz, M.D., to backtrack on his prior support for l-carnitine supplements. Once a proponent, Oz rescinded his claim that l-carnitine could help you lose fat. He issued a warning not to take carnitine.

Rarely Needed

Who might need carnitine supplements?

A preterm infant who cannot make enough carnitine may need to supplement with this compound. A rare genetic defect called primary carnitine deficiency may also require supplementation.  

For everyone else, it’s best to give carnitine a wide berth. If you’re a fan of energy drinks, read the ingredients and avoid those that contain l-carnitine. The occasional steak won’t do you in, but you’re best off limiting your consumption of red meat to the occasional few bites.