L-carnitine—also known as levocarnitine—is an amino acid that occurs naturally in the body and is available as a supplement. Some studies report weight loss results of 2 to 3 pounds with L-carnitine, but these results are mixed and more research is needed. In some cases, weight gain is actually the goal of using L-carnitine supplements.
L-carnitine aids in metabolism and can be used to supplement your body's natural carnitine to produce energy and remove toxins from cells. Because of this action, L-carnitine is sometimes taken to improve physical performance, or used when treating conditions such as end-stage kidney failure.
In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says. When choosing a supplement, look for third-party tested products and consult a healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.
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Does L-Carnitine Aid Weight Loss?
L-carnitine moves fatty acids into the cells to produce energy, so it has been assumed that it can help with weight loss. Some studies report L-carnitine weight loss results that support this theory but more research is needed for conclusions to be drawn.
A literature review that looked at 37 randomized control trials found that L-carnitine decreased body weight by 1.21 kilograms (2.66 pounds). The modest weight reduction was primarily seen in people who also ate a low-calorie diet and exercised.
L-Carnitine and Obesity
People diagnosed with obesity or overweight may improve their weight, waist circumference, and fat mass when treatment includes L-carnitine. There was less evidence of improved body fat percentage, according to a 2020 analysis of L-carnitine research studies.
Other Studied Uses
L-carnitine is a crucial component of energy production in the body. L-carnitine also helps to move toxins out of the cells. It may help with various symptoms of different diseases and conditions, as outlined below.
Alzheimer's Disease
Alzheimer's disease is the most common type of dementia. It is a progressive condition causing irreversible damage to nerve cells in the brain. It can be treated by preventing the breakdown or increasing the levels of the neurotransmitter acetylcholine.
Researchers have studied L-carnitine to determine if it can help produce acetylcholine.
A 2020 review of several articles regarding the use of L-carnitine for dementia and Alzheimer's disease found mixed results. Many of the studies reviewed showed favorable outcomes with L-carnitine use, whereas other studies showed minimal to no results.
Further research is needed on the effects of L-carnitine on people with Alzheimer's disease.
Heart Disease
L-carnitine supplements might aid in cardiovascular health by decreasing inflammation markers and reducing the likelihood of fatal irregular heart rhythms in people with heart disease.
A study from 2017 found benefits from L-carnitine supplementation in people with chronic heart failure. Improvements in several areas of heart function included cardiac output and left ventricular ejection fraction.
Other studies have found that L-carnitine supplementation caused negative effects on the cardiovascular system in people diagnosed with an underlying metabolic disorder or predisposed to cardiovascular risk. Research still needs to be conducted to determine if L-carnitine supplementation is an effective treatment for cardiovascular disease.
Kidney Disease
People receiving peritoneal dialysis treatment for renal (kidney) failure often demonstrate L-carnitine deficiency. This deficiency is associated with symptoms that include:
- Anemia
- Fatigue
- Cardiomyopathy (heart disease affecting the heart muscle)
- General muscle weakness
Supplemental L-carnitine is not recommended in all cases, but some people may benefit when L-carnitine is added to the fluid used for dialysis. More study is needed to understand this use.
Athletic Performance
Carnitine preserves fuel for the muscles and promotes the breakdown of fats into energy. As a result, some people take L-carnitine supplements to improve their athletic performance.
However, research has shown no proof that L-carnitine supplements improve physical exercise performance.
Fertility
L-carnitine has been used successfully to improve fertility. Research showed that supplementation improved sperm motility.
Other research has shown that L-carnitine supplementation improved ovulation and pregnancy rates in those with polycystic ovary syndrome (PCOS). People with PCOS who took the supplement had 64.4% higher ovulation rates. It also improved pregnancy rates and lessened miscarriages in those with PCOS.
Daily Dosage
Carnitine is made in the liver, kidney, and brain. The body stores 95% of carnitine in the heart and skeletal muscles. The body needs 15 milligrams (mg) per day of carnitine from either outside sources—like food—or from the body which makes its own carnitine.
Most people who eat a diet consisting of both meat and nonmeat sources will consume between 24 and 145 mg of carnitine each day. However, people who follow a vegan diet will likely consume only 1.2 mg per day.
Oddly, diet does not seem to influence how much carnitine the body makes. According to the National Institutes of Health, a person who eats a vegan diet still produces 14.4 mg of carnitine per day.
Since carnitine is not considered an essential nutrient, there are no recommended daily amounts for supplements.
Types of L-Carnitine Supplements
L-carnitine is a type of carnitine. There are several forms of carnitine available for supplementation. They include:
- L-carnitine: This is the most popular and least expensive form of carnitine. Its absorption rate (the amount made available for the body to use) is 14% to 18%, much lower than carnitine found in foods.
- Acetyl-L-carnitine: This is absorbed in the gut more easily and crosses the blood-brain barrier. As a result, it's more likely to be used in patients with Alzheimer's disease.
- Propionyl-L-carnitine: This form of carnitine is used in those with heart and peripheral vascular diseases.
Carnitine is typically taken as an oral supplement but can be given through an intravenous (IV) line.
Side Effects and Safety
There are potential side effects when too much L-carnitine is taken. They include:
- Vomiting
- Nausea
- Diarrhea
- Abdominal cramps
- Muscle weakness
- Foul body odor
- Seizures
Always talk to a healthcare provider before starting a carnitine supplement.
Who Can Benefit from Supplements?
L-carnitine supplements may offer benefits to specific users, including:
- People born with genetic conditions that lead to L-carnitine deficiency. This can include some autistic children.
- Those looking to boost their athletic performance
- People taking medications that lower carnitine levels in the body, like those that treat seizures or antibiotics
- Certain people treated for kidney failure
People who lose muscle due to cancer diagnosis and treatment (called cachexia) may benefit from L-carnitine supplements, too, but research results haven't shown a strong benefit and more study is needed. Always talk to a healthcare provider before starting a carnitine supplement.
Food Sources
The best source of L-carnitine is in food. The body's ability to absorb L-carnitine in food is much higher than in a supplement. The best sources (listed from greatest source to lowest) of L-carnitine include:
- Beef, including steak and ground beef
- Whole milk
- Cod
- Chicken breast
- Ice cream
- Cheese
Summary
L-carnitine is an amino acid that is produced in the body and is found in many animal-based food products. It produces energy and removes toxins from the cells. L-carnitine is often advertised as a supplement to help weight loss, improve physical performance, and more.
Research still needs to be done to confirm the effectiveness of L-carnitine supplementation. Always talk to a healthcare provider before starting a supplement as it may adversely interact with other medications or affect certain conditions.
