L-carnitine, also known as levocarnitine, is a naturally occurring amino acid structure that the body produces. 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. It is a chemical that is made in the human brain, liver, and kidneys. It helps the body turn fat into energy.
L-carnitine is important for heart and brain function, muscle movement, and many other body processes. The body can convert L-carnitine to other chemicals called acetyl-L-carnitine and propionyl-L-carnitine. But it’s not clear whether the benefits of these other carnitines are the same.
L-carnitine is used to increase L-carnitine levels in people whose natural level of L-carnitine is too low. Some people also use L-carnitine for conditions of the heart and blood vessels, serious kidney disease, and many other conditions, but there is no good scientific evidence to support these uses.
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.
What is L-carnitine?
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.
Chemical and physical properties
IUPAC Name: (3R)-3-hydroxy-4-(trimethylazaniumyl)butanoate
Molecular Weight (Molar Mass): 161.1989 g/mol
Molecular Formula (Structural Formula): C7H15NO3
SMILES: [O-]C(CC@@HCN+©C)=O
InChIKey Identifier: PHIQHXFUZVPYII-ZCFIWIBFSA-N
CAS Number: 541-15-1
MDL Number: MFCD00038747
Melting point: 197-212 °C
Solubility in water: 2500 g/L (20 °C)
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.
L-carnitine is an amino acid produced by the body that’s also found in food and supplements. Some studies suggest it may offer some health benefits, including increased weight loss, improved brain function, and more.
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.
Different types of L-carnitine
L-carnitine is the standard biologically active form of carnitine, which is found in your body, foods, and most supplements.
Here are several other types of carnitine:
D-carnitine: This inactive form has been shown to reduce blood levels of carnitine and increase fat buildup, leading to liver inflammation and oxidative stress.
Acetyl-L-carnitine: Often called ALCAR, this is possibly the most effective form for your brain. Studies suggest that it may benefit people with neurodegenerative diseases.
Propionyl-L-carnitine: This form is well-suited for circulatory issues, such as peripheral vascular disease and high blood pressure. According to some older research, it may boost the production of nitric oxide, which improves blood flow.
L-carnitine L-tartrate: This is commonly added to sports supplements due to its rapid absorption rate. It may aid muscle soreness and recovery in exercise.
For most people, acetyl-L-carnitine and L-carnitine seem to be the most effective for general use. However, you should always pick the form that’s best for your personal needs and goals.
Role in your body
L-carnitine’s main role in your body involves mitochondrial function and energy production.
In cells, it helps transport fatty acids into the mitochondria, where they can be burned for energy.
More than 95% of your L-carnitine stores are contained in your muscles, along with trace amounts in your blood, liver, heart, and kidneys.
L-carnitine may help increase mitochondrial function, which plays a key role in disease and healthy aging.
Newer research illustrates the potential benefits of carnitine’s different forms, which may be used for various conditions, including heart and brain diseases.
A variety of therapeutic roles have been attributed to this amino acid, which undergoes rapid conversion from both lysine and methionine. The process of conversion is dependent upon adequate vitamin C being present. The supply of carnitine is especially enhanced by lysine ingestion, as compared with other amino acid precursors of carnitine such as threonine and tryptophan.
It is suggested, based on recent studies, that men have a higher need for carnitine than women. Higher levels are found in blood in men than women, and men have high levels present in the epididymis of the testes. Lysine depletion in animals results in infertility as a result of the loss of sperm motility.
Some researchers suggest that although this amino acids is not a vitamin it may be an essential nutrient in newborn infants, due to inadequate ability to synthesize it; and in adults with genetic limitations in their ability to convert methionine or lysine to carnitine.
L-Carnitine has been shown to have a profound involvement in the metabolism of fat, and in the reduction of triglycerides. Oxidation of triglycerides occurs when 1 g to 3 g of carnitine are administered daily. This is of potential value in conditions as diverse as intermittent claudication; poor hand and foot circulation; myocardial infarction and kidney disease. It transfers fatty acids across the membranes of the mitochondria (energy producing centres in all body cells), where they can be utilized as sources of energy.
A variety of other conditions have been suggested as being potential beneficiaries of carnitine supplementation, including muscular dystrophy, myotonic dystrophy, and limbgirdle muscular dystrophy, since these lead to carnitine loss in the urine and therefore greater requirements.The application to the stimulation of fat metabolism leads to possible benefits in cases of obesity. Since fat is more readily mobilized, and clearance is more rapid, with the use of carnitine, there is every reason to expect that a clinical application in this direction will be forthcoming with further research.
Carnitine has been shown to be useful in conditions of ketosis (build up of acid wastes in the blood) in individuals on diets which produce the accumulation of ketone bodies, or fat waste products, in the blood. Such a build up can acidify the blood, resulting in calcium, magnesium and potassium loss, and can indeed be life-threatening. Fat metabolism requires carnitine to be adequately present. In scurvy the fat levels of the blood are high, and this is thought to be as a result of the relationship which exists between vitamin C and carnitine. A low level of vitamin C will result in apparent carnitine deficiency.
Dietary sources
Carnitine is synthesized in the liver by humans as well as being a part of the diet in the form of muscle and organ meats. It is not found in vegetable forms of protein. This amino acid is not essential
Carnitine is predominantly found in animal products, particularly in red meat. Poultry, fish, and dairy products also contribute to carnitine intake, whereas vegetables, fruits, and grains contain minimal amounts. The bioavailability of dietary carnitine ranges from approximately 63% to 75%, although the bioavailability of acetyl-L-carnitine has not been extensively researched.
Specific information on the carnitine content of various foods is limited. The U.S. Department of Agriculture’s (USDA’s) FoodData Centralexternal link disclaimer does not include the carnitine content of foods.
Below is a list of several foods along with their approximate carnitine content per serving, based on several small studies.
• A 3-ounce serving of cooked beef steak - 42–122 mg.
• Cooked ground beef, in a 3-ounce serving - 65–74 mg.
• One cup of whole milk - 8 mg.
• In a 3-ounce serving of cooked codfish - 3–5 mg.
• Cooked chicken breast, in a 3-ounce serving - 2–4 mg.
• Enjoying ½ cup of ice cream - 3 mg.
• Cheddar cheese, in a 2-ounce serving - 2 mg.
• Two slices of whole-wheat bread - 0.2 mg.
• For a ½ cup of cooked asparagus - 0.1 mg.
L-carnitine Uses
Because L-carnitine helps move more fatty acids into your cells to be burned for energy, it’s sometimes used as a weight loss supplement.
L-carnitine deficiency. Taking L-carnitine by mouth or by IV is effective for treating L-carnitine deficiency caused by certain genetic diseases or other disorders. It’s approved by the FDA for this use. IV products can only be given by a healthcare provider.
Chest pain (angina). Taking L-carnitine by mouth or by IV seems to improve exercise tolerance in people with chest pain. Taking L-carnitine along with standard treatment also seems to reduce chest pain and improve exercise ability in people with cardiac syndrome X. People with this condition have chest pain but not blocked arteries. IV products can only be given by a healthcare provider.
Heart failure and fluid build up in the body (congestive heart failure or CHF). Taking L-carnitine by mouth or by IV seems to improve symptoms and increase exercise ability in people with heart failure. IV products can only be given by a healthcare provider.
High levels of cholesterol or other fats (lipids) in the blood (hyperlipidemia). Taking L-carnitine by mouth or by IV can improve cholesterol and triglyceride levels by a small amount. IV products can only be given by a healthcare provider.
Kidney failure. The FDA has approved giving L-carnitine by IV, but not by mouth, for kidney failure. This can only be given by a healthcare provider.
Conditions in a male that prevent a female partner from getting pregnant (male infertility). Taking L-carnitine by mouth, alone or together with acetyl-L-carnitine, increases sperm count and sperm movement in males with fertility problems. Some research shows that this increases the chance of pregnancy.
Swelling (inflammation) of the heart (myocarditis). Some children who have had diphtheria can develop myocarditis. Taking DL-carnitine by mouth seems to reduce the risk of myocarditis and death in these children.
Toxic side effects caused by the drug valproic acid. Toxicity caused by valproic acid seems to be linked with L-carnitine deficiency. Taking L-carnitine by mouth or by IV can prevent liver toxicity from valproic acid. IV products can only be given by a healthcare provider.
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