What to Know About the Amino Acid L-Carnitine

L-carnitine is an amino acid produced by the body and found in some foods and supplements. It may offer some health benefits, including increased weight loss, improved brain function, and more.

L-carnitine is a naturally occurring amino acid derivative that’s often taken as a supplement. It’s used for weight loss and may have an impact on brain function.

However, popular claims about supplements don’t always match up with the science.

Keep reading to learn more about the possible functions, risks, and benefits of L-carnitine.

What is L-carnitine?

L-carnitine is a nutrient and dietary supplement. It plays a crucial role in the production of energy by transporting fatty acids into your cells’ mitochondria.

The mitochondria act as engines within your cells, burning these fats to create usable energy. Your body can produce L-carnitineTrusted Source out of the amino acids lysine and methionine.

For your body to produce it in sufficient amounts, you also need plenty of vitamin CTrusted Source.

More than 95%Trusted Source of your L-carnitine stores are contained in your muscles, along with trace amounts in your blood, liver, heart, and kidneys.

You can also obtain small amounts by eating animal products like meat and dairy products.

People who eat plant-based diets or those with certain genetic issues may be unable to produce or obtain enough L-carnitine, which makes it a conditionally essential nutrient.

Does it aid weight loss?

L-carnitine helps move more fatty acids into your cells to be burned for energy, so it’s sometimes used as a weight loss supplement.

A 2020 reviewTrusted Source of 37 studies found that L-carnitine supplementation significantly reduced body weight, body mass index (BMI), and fat mass. However, it had no effect on belly fat or body fat percentage.

Another 2021 review in 1,239 people with type 2 diabetes also found that taking 2 grams (g) of L-carnitine daily for at least 2 weeks helped promote weight loss.

Still, more research is needed to understand how it may impact long-term weight loss.

Furthermore, while it may aid in weight loss for some people, consider speaking with a dietician to develop a thorough diet and exercise regimen first.

Effects on brain function

L-carnitine may benefit brain function.

Some research suggests that the acetyl form, acetyl-L-carnitine (ALCAR), may help prevent age-related mental decline and improve markers of learning.

In fact, a 2018 study found that taking 1,500 milligrams (mg) of ALCAR daily for 28 weeks significantly improved brain function in people with dementia.

However, other studies have turned up mixed results.

For instance, a 2017 review of two studies showed that taking L-carnitine for 3 days had no effect on markers of brain function — including reaction time, vigilance, immediate memory, and delayed recall — in young adults without cognitive impairment.

Therefore, more research is needed on the potential benefits of supplementation.

Heart health

Some studies demonstrate that L-carnitine could benefit several aspects of heart health.

For example:

• A 2019 reviewTrusted Source found that L-carnitine significantly reduced diastolic blood pressure, especially in people with overweight and obesity.
• A 2017 analysis showed that L-carnitine may improve heart function and decrease symptoms in people with congestive heart failure.
• A 2019 reviewTrusted Source showed that L-carnitine may reduce total and LDL (bad) cholesterol while increasing HDL (good) cholesterol in people at risk for heart disease.

Food sources

You can get small amounts of L-carnitine from your diet by eating meat and dairy products.

The best sources of L-carnitine are:

• Beef: 139 to 143 mg per 3.5 ounces (oz), or 100 g
• Pork: 25 to 61 mg per 3.5 oz (100 g)
• Chicken: 13 to 34 mg per 3.5 oz (100 g)
• Cow’s milk: 40 mg per 3.5 oz (100 g)
• Hard cheese: 3 mg per 3.5 oz (100 g)

Interestingly, food sources of L-carnitine have a greater absorption rate than supplements.

According to a 2004 study, 57% to 84%Trusted Source of L-carnitine is absorbed when it’s consumed from food, compared to only 14% to 18% when taken as a supplement.

Your body also produces L-carnitine naturally from the amino acids methionine and lysine if your stores are low.

As such, L-carnitine supplements are only necessary in special cases, such as disease treatment.

Should you take it?

Your L-carnitine levels are influenced by how much you’re eating and how much your body is producing.

Vegans and vegeterians

L-carnitine levels are often lowerTrusted Source in vegetarians and vegans since they restrict or avoid animal products.

Therefore, vegetarians and vegans may want to consider L-carnitine supplements, which can help normalize carnitine levels in the blood and muscles.

Older adults

Older adults may also benefit from L-carnitine supplements.

A 2016 study found that taking 1.5 g of L-carnitine per day for 10 weeks improved functional status and frailty in older adults.

On the other hand, a 2018 study showed that L-carnitine supplementation had no effect on muscle strength or markers of inflammation in older women.

Chronic conditions

The risk of deficiency is higher for those with diseases like cirrhosis and kidney disease. If you have one of these conditions, a supplement may be beneficial.

However, as with any supplement, you should speak with a doctor before taking L-carnitine.

Dosage recommendations

Studies on the potential benefits of L-carnitine have used a wide range of doses.

Dosage varies from study to study and may vary depending on the form of carnitine you take:

• Acetyl-L-carnitine: This form is best for brain health and function. Doses vary from 500 to 3,000 mg per day.
• L-carnitine L-tartrate: This form is most effective for exercise performance. Doses vary from 1,000 to 4,500 mg per day.
• Propionyl-L-carnitine: This form may help improve blood flow in those with high blood pressure or related health conditions. A 2005 study used a dose of 2 g per dayTrusted Source.

Frequently asked questions

Does L-carnitine affect sleep?

Some research suggests that taking 500 to 510 mg of L-carnitine daily may help treat narcolepsy, a sleeping condition characterized by abnormal sleeping patterns.

Is L-carnitine good for females?

Some researchTrusted Source suggests that L-carnitine may reduce body weight, BMI, and belly fat in people with polycystic ovary syndrome (PCOS).

If you’re pregnant or have recently delivered, consider speaking with a doctor about your carnitine levels. People who are pregnant have a higher riskTrusted Source of carnitine deficiency.

Who should not take carnitine?

People who are taking certain typesTrusted Source of antibiotics and anticonvulsants should speak with a doctor before taking L-carnitine, as this supplement may interact with the medications.

The bottom line

L-carnitine is an amino acid that may help support weight loss, brain function, and disease prevention.

It’s produced naturally in your body, but it’s also found in foods like meat and dairy products. Supplements may benefit those with lower levels, such as older adults, vegans, and vegetarians.

Consider speaking with a healthcare professional before taking L-carnitine. They could help you decide whether it’s appropriate and recommend the best dosage.