What to know about L-carnitine

L-carnitine, also known as levocarnitine, is a naturally occurring amino acid structure that the body produces. People can also get it from their diet or take it in the form of an oral supplement. L-carnitine plays a critical role in energy production, as it converts fat into energy.

Most people will get enough L-carnitine from their diet or their body’s production of this compound. Those with low L-carnitine levels may benefit from taking an oral supplement, though.

As well as supporting energy production, L-carnitine may help some other functions in the body, such as maintaining general brain function and reducing the risk of certain disorders.

Some people may experience mild side effects when increasing their L-carnitine intake, especially with long-term use.

In this article, we explore what the current research says about L-carnitine, including its benefits, effectiveness, and side effects.

What is L-carnitine?

l carnitine pills in a bowl
A person can take L-carnitine in supplement form.

L-carnitine is a type of carnitine, which is a derivative of amino acids. Amino acids combine to make proteins, which carry out many essential tasks in the body. Carnitine helps the body break down fatty acids and turn them into energy to power the cells.

L-carnitine is a conditionally essential nutrient, meaning that the body can generally make enough of it, but, in some cases, a person may have to get the compound from food or oral supplements if they cannot make enough.

In the body, the liver and kidneys create L-carnitine from the amino acids lysine and methionine. The kidneys can also store L-carnitine for later use and eliminate the excess through the urine stream.

Types

Carnitine is a broad term that describes a few different compounds. L-carnitine is a more common form of carnitine, present in the body and many supplements. Other forms of carnitine include:

  • Acetyl L-carnitine: This form, sometimes known as ALCAR, also plays a role in metabolism. It possesses neuroprotective properties that may help protect the nervous system.
  • D-carnitine: This type is the optical isomer (mirror image) of L-carnitine. It is toxic to the body, as it may inhibit the absorption of other forms of carnitine.
  • L-carnitine L-tartrate: Athletes may use this type in the form of sports supplements. Research suggests that it may be useful in minimizing muscle soreness and aiding recovery.
  • Propionyl-L-carnitine: This form displays pain relieving and antirheumatic properties, and it may benefit heart health.

Possible benefits

L-carnitine, and carnitine in general, is a key component in creating energy for the cells. Its main function, helping break down fatty acids for use as energy, keeps the body’s cells powered and working efficiently.

L-carnitine also has a secondary function of helping remove some waste products from the cells to prevent them from accumulating and causing problems.

In addition to its core functions, L-carnitine may also pose some other benefits to the body. These include:

Heart health

L-carnitine may help with some markers of heart health, although the research is still ongoing.

Supplementation may help improve L-carnitine levels in a failing heart, which could boost heart health and circulation in the short term following a heart attack. Supplementation may also help with symptoms of heart failure, such as chest pain and arrhythmia.

Cancer treatment

At times, cancer treatments, such as chemotherapy, may cause a person to become deficient in L-carnitine. In these cases, L-carnitine supplements may help reduce symptoms such as fatigue and weakness.

Researchers are currently studying the compound as a possible way to prevent tissue damage due to chemotherapy, but this research is in the early stages.

Kidney or liver disease

As the kidneys and liver help create and use L-carnitine, disease in these organs or organ failure may lead to L-carnitine deficiency. Doctors may recommend L-carnitine supplementation in these cases to support the function of the kidneys and liver and prevent deficiency.

Side effects

Most people tolerate L-carnitine well. However, some individuals may experience digestive side effects when taking L-carnitine. These include:

  • stomach cramps
  • nausea
  • vomiting
  • diarrhea

Some people may also complain of a “fishy” body odor, which is not generally harmful but may be bothersome.

Some studies suggest that high levels of L-creatine may raise the long-term risks of cardiovascular diseases, such as atherosclerosis.

L-carnitine supplements may interact with certain antibiotics or anticonvulsants. Anyone considering taking L-carnitine should talk to their doctor to discuss any medications they are taking and the possible drug interactions.

How and when to take

The best amount and form of L-carnitine may vary depending on the person’s reason for wanting more of this compound.

Adults with a good overall health status

The National Institutes of Health (NIH) note that healthy people do not need extra L-carnitine from food or supplements. The liver and kidneys will create enough to meet their daily needs.

Even though the body produces it naturally, carnitine is widely available in a number of simple foods. Animal proteins, such as fish, red meat, and poultry, are some of the best sources.

According to the NIH, adults who eat a mixed diet that includes red meat and other animal products get about 60–180 milligrams (mg) of carnitine per day. People who avoid animal products, such as those following a vegan diet, may get roughly 10–12 mg from their diet.

However, the kidneys can store carnitine for later use, so people’s overall levels will be about the same, regardless of their diet. The kidneys also eliminate excess carnitine through urine to maintain healthful concentrations.

Generally speaking, otherwise healthy adults do not need to take L-carnitine to support their health.

Athletes

Some athletes take extra L-carnitine, believing that it will boost their athletic performance. L-carnitine availability seems to limit muscle metabolism during very high intensity exercise. So, in theory, supplementing carnitine during workouts may support exercise performance.

However, a study in Molecules notes that the evidence for this practice is lacking. While many athletes take L-carnitine, years of research does not provide conclusive evidence to support these claims.

For weight loss

As L-carnitine helps burn fatty acids for energy, many people assume that taking more of it may help them lose weight. More research is necessary, but some studies support this idea.

In a review of nine different trials, researchers found some evidence to support this claim. They suggest that participants who took L-carnitine lost an average of 1.3 kilograms (2.9 pounds) more than those who did not.

However, L-carnitine cannot replace healthful habits, such as a proper diet and regular exercise.

Dosage recommendations

People who wish to take L-carnitine should talk to a doctor first. The doctor may have additional recommendations to support any treatment that the person needs and can help them avoid possible reactions and interactions.

Most people tolerate L-carnitine well. The recommended dosage is roughly 1–3 grams per day. However, people with genetic abnormalities or other conditions causing a lack of L-carnitine should talk to their doctor for a more specific dosage.

Summary

L-carnitine is an amino acid that the body naturally produces. In people with good health, the liver and kidneys produce and store enough of the compound to prevent deficiency.

People with L-carnitine deficiencies may need to get the compound through their diet or as a supplement. It is advisable to talk to a doctor before taking an L-carnitine supplement.

Some people may wish to take L-carnitine supplements for their potential benefits, such as aiding athletic performance or weight loss. However, more research is necessary to confirm these benefits.

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