A naturally occurring amino acid derivative, L-carnitine is often taken as a supplement. There exist L carnitine liquid, tablets, and capsules.
These supplements are thought to have an impact on brain health and function, as well as weight loss.
However, some popular claims about this supplement are not backed with science.
Here we examine the potential benefits, side effects, sources, and dosage of L-carnitine supplements. We also explain herein how this nutrient functions in your body.
What is L-carnitine?
A nutrient and dietary supplement, L-carnitine plays an important role in energy production. It transports fatty acids into the mitochondria, which acts as engines within your cells, thereby burning fats and creating usable energy.
Your body is able to produce L-carnitine from the amino acids methionine and lysine, but you will also need sufficient amounts of vitamin C to produce plenty of this.
Moreover, eating animal products like fish, chicken, or meat can help you obtain small amounts of L-carnitine.
L-carnitine is a conditionally essential nutrient. Vegans or individuals with certain genetic issues may not be able to produce or get enough L-carnitine.
Different types of carnitine
L-carnitine is a more common active form of carnitine, which is present in the body, foods, and many supplements. Here are the different types of carnitine:
Propionyl-L-carnitine. This form may help increase the production of nitric oxide, thereby improving blood flow. It is best for circulatory issues, including high blood pressure and peripheral vascular disease.
L-carnitine L-tartrate. This type of carnitine may aid muscle soreness and recovery in exercise, which is why it is commonly added to sports supplements. Moreover, it has a rapid absorption rate.
Acetyl-L-carnitine. This type is often called ALCAR and is possibly the most effective form for your brain. In fact, it has been suggested to benefit people with neurodegenerative diseases.
D-carnitine. This inactive form inhibits the absorption of other more useful forms of carnitine, which may cause a carnitine deficiency in your body.
Although L-carnitine and acetyl-L-carnitine seem to be the most effective type for general use for most people, you should choose the form that is fitting for your goals and personal needs.
Its role in the body
The main role of L-carnitine in your body involves energy production and mitochondrial function.
L-carnitine helps transport fatty acids into the cells’ mitochondria, where they are burned to be used for energy. It may also help boost mitochondrial function, which is crucial in disease and healthy aging.
Recent research demonstrated that the different forms of carnitine may be beneficial for various conditions, such as brain and heart diseases.
L-carnitine for weight loss
In theory, the use of L-carnitine for weight loss makes sense.
You might think that it would boost fat burn and weight loss as it helps move more fatty acids into the cells to be burned for energy.
However, considering that the human body is particularly complex, both human and animal study results are mixed.
An 8-week study in women who exercised four times every week observed no difference in weight loss between participants administered with L-carnitine and those who weren’t.
Plus, five of the L-carnitine-administered participants experienced diarrhea and nausea.
In addition, another human study examined the effect of L-carnitine on fat burning during a 90-minute stationary bicycle workout, and found that taking supplements for four weeks did not increase fat burning.
However, one analysis of nine studies—mostly in older adults and obese individuals—observed an average of 1.3 kg weight loss while taking L-carnitine.
With that, further human study is necessary to confirm the benefits of L-carnitine in a younger and more active population.
Although L-carnitine may promote weight loss for older adults and obese individuals, a proper diet and exercise regimen must be held in a paramount regard.
Its effects on brain function
L-carnitine may also have positive effects on brain function.
Acetyl-L-carnitine (ALCAR) has been suggested in some animal studies to help improve markers of learning and prevent age-related mental decline.
Moreover, taking acetyl-L-carnitine daily has been found in human studies to help reverse the decline in brain function associated with brain diseases, such as Alzheimer’s.
It also showed similar effects on the general brain function in older adults who have no brain conditions, like Alzheimer’s.
It may even protect the brain from cell damage in specific cases.
In fact, a 90-day study found significant improvements in all measures of brain function in alcoholic people who took 2 grams of acetyl-L-carnitine every day.
Further research on long-term benefits for healthy individuals is however necessary.
Other health benefits
L-carnitine supplements have been linked to a few more health benefits.
Heart health
L-carnitine supplements have been found in some studies to potentially reduce blood pressure and the inflammatory process linked to heart disease.
One study showed that a 2-gram acetyl-L-carnitine a day leads to an almost 10-point drop in systolic blood pressure, which is an important indicator of heart health and disease risk.
L-carnitine has also helped improve patients with severe heart disorders, such as chronic heart failure and coronary heart disease.
Moreover, a 12-month study in participants who took L-carnitine supplements observed a reduction in heart failure and deaths.
Exercise performance
When it comes to the effects of L-carnitine on sports performance, the evidence is mixed.
However, mild benefits associated with larger, long-term doses have been noted in several studies.
The benefits of L-carnitine’s benefits may take weeks or even months to happen; this differs from supplements like creatine or caffeine, which can improve sports performance directly.
L-carnitine may also benefit the following:
Red blood cell production. It may help increase the production of red blood cells, which carries oxygen from the lungs to other parts of the body and muscles.
Muscle oxygen supply. It may also help increase oxygen supply to your muscles.
Muscle soreness. It may lessen muscle soreness after exercise.
Recovery. It may also promote exercise recovery.
Stamina. It may increase blood flow and the production of nitric oxide, which can help reduce fatigue and delay discomfort.
Type 2 diabetes
L-carnitine may also improve type 2 diabetes symptoms, as well as its associated risk factors.
A study in people with type 2 diabetes who took anti-diabetic medication found carnitine supplements to significantly lower blood sugar levels.
It may also increase a key enzyme called AMPK, which may improve the body’s ability to utilize carbs, thereby combating diabetes.
Safety and side effects of L-carnitine
Two grams of L-carnitine or less per day is relatively safe for most people and free from any serious side effects.
A study found no negative effects on people who took 3 grams of L-carnitine every day for 21 days.
In addition, a review of the safety of L-carnitine demonstrated that ~ 2 grams per day may be safe for long-term use, but some mild side effects, including stomach discomfort and nausea, were observed.
However, L-carnitine supplements may also cause your blood levels of trimethylamine-N-oxide (TMAO) to increase over time. It can be noted that high TMAO levels are associated with an increased risk of atherosclerosis, which is a coronary artery disease that involves chest pain.
Further studies on L-carnitine supplements’ safety are necessary.
Food sources
Small amounts of L-carnitine can be obtained from your diet by eating animal products, such as fish, meat, and milk. Here are the best sources of L-carnitine, as well as its amount for every 3 ounces or 85 grams.
Fish: 5 mg of L-carnitine
Chicken: 3 mg of L-carnitine
Beef: 81 mg of L-carnitine
Pork: 24 mg of L-carnitine
Milk: 8 mg of L-carnitine
Food sources of L-carnitine have interestingly a higher absorption rate as compared with supplements.
One study showed that only 14–18% of L-carnitine is absorbed when taken as a supplement and 57–84% when it’s consumed from food.
Additionally, it can be noted that your body is able to produce L-carnitine from the amino acids lysine and methionine if your stores are low.
That said, L-carnitine supplements are only needed in certain conditions, such as disease treatment.
Should you take it?
Your L-carnitine levels depend on how much your body is producing and how much you’re consuming.
This makes vegetarians and vegans obtain only small amounts of L-carnitine, as they restrict consumption of animal products.
Therefore, these people may want to consider taking L-carnitine supplements. However, no studies have confirmed carnitine supplements’ benefits in vegetarians and vegans.
L-carnitine supplements may also benefit older adults. It has been found that your L-carnitine levels tend to go down as you age.
One study showed that 2 grams of L-carnitine increased muscle function and reduced fatigue in older adults. Other research also found acetyl-L-carnitine to help boost brain function and health as you age.
In addition, people with kidney disease and cirrhosis have been found to have a higher risk of deficiency; thus, taking L-carnitine supplements may be beneficial for them.
Before you take L-carnitine, you should speak with a healthcare provider first.
Dosage recommendations
The standard dosage recommendation for L-carnitine is 500–2,000 mg every day.
Different studies provide various dosage recommendations. Below is an at-a-glance of the dose and use for each form.
L-carnitine L-tartrate. Most effective for exercise performance, L-carnitine L-tartrate doses can range from 1,000 to 4,000 mg every day.
Propionyl-L-carnitine. The recommended dosage for this form varies from 400 to 1,000 mg per day. It helps improve blood flow in people with high blood pressure or related health conditions.
Acetyl-L-carnitine. This form may be beneficial for brain health and function. Its recommended dosage can range from 600 to 2,500 mg per day.
Two grams of L-carnitine per day seem safe and effective for long-term use.
Conclusion
Although best known as a fat burner, L-carnitine is unlikely to cause significant weight loss.
However, evidence supports its use for brain function, disease prevention, and health.
People with lower L-carnitine levels, such as vegetarians, vegans, and older adults, may benefit from supplements—may it be L-carnitine liquid, tablets, or capsule.
Out of all the different forms of carnitine, L-carnitine and acetyl-L-carnitine seem to be the most effective and most popular.
