woman taking a selfie in training clothes

What is L-Carnitine and what is it for?

L-carnitine is a substance produced by the body with the help of two amino acids: lysine and methionine. 

As an athlete, vegan, or a person interested in nutrition, you have probably come across the term L-carnitine, perhaps in advertising as a dietary supplement or as a miracle cure for burning fat.

Structure and synthesis

L-carnitine is a protein compound that the body needs for fat metabolism and it also plays an important role in carbohydrate metabolism.

The body can produce carnitine from methionine and lysine in the presence of certain vitamins and the trace element ironThese are two essential amino acids, which means that the body cannot produce them on its own. They have to be consumed with food.

Foods that contain proteins such as meat, fish, nuts, eggs, and soy, in particular, are high in these substances. Once ingested, methionine and lysine become their active forms in the body and are available for protein synthesis and to build carnitine.

It breaks down into two forms, one of which is L-carnitine. A deficiency of the two amino acids leads to the fact that the synthesis reactions deteriorate and a deficit arises. Therefore, it is good to know that you can supply L-carnitine to your body directly from food and thus satisfy your needs.

The body produces carnitine itself, but to an insufficient degree, so additional intake must be made through food or dietary supplements. Since it is a protein- like substance, carnitine is found mainly in meat (preferably lamb and sheep meat).

L-carnitine increases performance, which endurance athletes in particular appreciate. Due to increased performance, it is possible that fatigue time may be significantly delayed. It is especially effective for marathon runners, rowers, or long-distance runners, as well as racing cyclists.

L-carnitine also has the ability to stimulate fat metabolism. The substance is known to improve regeneration through absorption.

The functions of L-carnitine

L-carnitine is important for carbohydrate and fat metabolism. It absorbs free fatty acids in cell plasma and transports them to the mitochondria. These organelles, also known as cell power plants, are responsible for energy metabolism and are very numerous, for example, in muscle cells.

The long-chain fatty acids can only move through the mitochondrial cell membrane if they are bound to L-carnitine. Since it acts as a bio carrier. If this link does not exist, they remain in the cell plasma and are not available for power generation.

In this case, they are converted to their storage form and deposited as depot fat in various tissues, such as subcutaneous fat or liver parenchyma. The result may be obesity. Various enzymes play an important role in this process.

L-carnitine is important in carbohydrate metabolism because it increases the sensitivity of insulin receptors in cell membranes. Therefore, insulin can work more effectively and glucose can enter cells better and faster.

This is an important mechanism for regulating blood sugar levels and optimizing energy production in the mitochondria.

Need, safety and supply of L-carnitine

An average of 20-25 grams is stored in the human body. About 98% of the supply is in the heart and skeletal muscles. This is due to the fact that these tissues have a high energy rotation. 

Daily needs depend on several factors. Therefore, it can fluctuate and averages between 16 and 23 milligrams in a 70 kg man. It can increase significantly during physical work, serious illnesses, sports activities, or psychological stress. 

As a rule, the need is met through food, on the one hand through a direct intake and, on the other hand, through the two protein building blocks that are used to establish the connection. 

Studies have shown that the level in cells does not increase due to higher intake and that fat turnover does not increase. This is due to the fact that excess molecules, no matter how they were absorbed, are broken down immediately through the metabolism of urea and excreted in the urine. 

An exaggerated intake of food supplements, for example, is ineffective and, on the contrary, can have a negative effect. A strong concentration can cause the body to speed up its own production because sensors in the blood indicate an adequate supply. 

Therefore, you should simply pay attention to an adapted diet instead of, as it is sometimes recommended, ingest up to 3 grams per day through nutritional supplements. 

An exaggerated intake of food supplements, for example, is ineffective and, on the contrary, can have a negative effect. A strong concentration can cause the body to speed up its own production because sensors in the blood indicate an adequate supply. 

woman doing bycicles

Carnitine content in food

As already mentioned, daily needs in the context of a healthy diet are easily met. Meat, especially red varieties like a lamb, game meat, and beef, contains a lot of L-carnitine, but vegetables, fruits, and nuts contain very little.

Vegetarians mainly consume low-content foods, but the daily supply is generally guaranteed. It is more difficult for vegans. Vegetables, fruits, nuts, and grains contain very little substance and an adequate supply may be compromised. Therefore, as a vegan, you need to pay attention to the careful composition of your food.

Mushrooms, for example, have a relatively high content of protein compound. On the other hand, you don’t have to worry too much, because scientists have discovered that the metabolism of vegans is adapted so that there is no lack of energy.

Enzymes, which in cooperation with L-carnitine ensure that long-chain fatty acids are transported to cells, improve their efficiency. They gradually increase their effectiveness and work up to 60% more efficiently than non-vegans.

This means that the supply of the cells is sufficient even with a smaller supply.

Carnitine deficiency

As a vegan, you generally don’t have to worry. There is a growing discussion about the fact that pregnant women and young children can experience the negative consequences of a deficiency.

In the first case, this is due to the fact that the mother’s iron level decreases during pregnancy, and insufficient L-carnitine is synthesized. This results in a deficiency for the mother while properly caring for the child.

In this case, you should not worry, because there have been no documented cases describing negative effects for the mother or child. Rather, the drop in iron level appears to be a sensible regulation to protect against infection.

The situation is similar to babies and children. Breast milk contains enough L-carnitine only in the first month, after which the level drops relatively quickly. On the other hand, babies cannot synthesize it by themselves.

This ability develops gradually in childhood and adolescence and only fully develops at 15 years. However, so far, no signs of deficiency have been found in infants or older children and adolescents unless there is a special disease.

It can also be assumed that the body prefers other protection processes.

Causes of L-carnitine deficiency

As you have seen, if you are healthy and have a balanced diet, the risk of developing a deficiency and causing health problems is very low.

On the one hand, the diagnosis is very difficult because the exact limit values ​​for the needs cannot yet be clearly established and not all the relationships have been scientifically clarified. On the other hand, the tissue tolerance threshold and the adaptability of bioactive substances in cells appear to be very high.

Lack of carnitine can arise in different ways:

Synthesis is impaired due to liver disease or insufficient intake of iron and vitamins B3, B6, B12, and folic acid. These vital substances play a key role in the construction of L-carnitine from the two amino acids mentioned above. They are often absent from a one-sided diet or from actual malnutrition.

Hereditary enzyme deficiencies impair or impair carrier function in the cell membrane. As a result, mitochondria do not have enough long-chain fatty acids for energy supply.

Due to an insufficient supply of nutrients as part of malnutrition or a very one-sided diet, the body does not ingest enough L-carnitine, as well as methionine and lysine. As a result, the synthesis rate and external supply are too low to meet real demand.

Deficiency due to illness

With certain diseases associated with diarrhea and increased excretion of water, but also with dialysis, there is a massive loss that the body cannot compensate for in the short term. The same effect is also produced due to a hereditary disease in which an increased release of the renal tubules is induced.

The energy requirement increases greatly under certain loads and can only be guaranteed with an adequate amount of long-chain fatty acids. To do this, there must be enough L-carnitine in the cell.

In the case of serious illnesses such as sepsissevere burns, or major gastrointestinal operations, the body may not be able to provide the capabilities necessary to meet energy requirements. In this case, it is a relative deficiency that disappears after the cause has been remedied.

Certain medications taken due to other conditions can affect both synthesis and function.

Regardless of the cause, the consequences of a defect are always the same. L-carnitine-dependent functions are impaired or completely prevented.

This can be a temporary process that disappears after the cause has been removed. Or the situation persists if the triggering cause cannot be eliminated. Without countermeasures, various symptoms can develop.

two women performing jumping squats

L-carnitine deficiency symptoms

As previously mentioned, the human body is highly capable of reacting to reduced L-carnitine absorption and production when healthy. The system can significantly increase both the efficiency of the substance and of the enzymes that control the function of the carrier in the cell membrane.

High loads, serious illness, great weight loss, and certain medications can lead to a real deficiency that the body cannot compensate for on its own.

As a result, symptoms related to functions appear and affect the entire system or specifically the muscles. Fat metabolism when impaired can have negative consequences. Since cells do not produce enough energy. This will reduce your performance.

On the other hand, unused fats are returned to the blood and lead mainly to an increase in fat levels in the blood. In the long term, this increases the risk of stroke and heart attack.

In a further step, the fatty compounds are stored and deposited in various tissues, especially the liver, muscles, heart, and other internal organs, as well as subcutaneous fat. The direct result is the development of obesity.

This can have serious consequences, especially for the heart and liver. The risk of heart attack increases in the heart and heart failure can develop. The liver is initially altered in its function, which is particularly noticeable in detoxification and other metabolic functions.

If this condition persists for a longer period of time, liver cirrhosis can developMuscles lose function through both processes. Their performance decreases and they tire quickly because there is not enough energy available.

If this condition does not change over a longer period of time, the contractile tissue is gradually replaced by fat. As a result, the muscles lose strength and elasticity. The risk of injury increases and atrophies develop.

Carbohydrate metabolism

L-carnitine is not only involved in fat metabolism, but also in carbohydrate metabolism. It increases the sensitivity of beta receptors in cell membranes to insulin and, therefore, promotes the absorption of glucose in cells.

With a deficiency, two things happen. On the one hand, less glucose is absorbed into the cells and the energy problem increases. On the other hand, more glucose molecules remain in the blood, and the blood sugar level increases.

This process may play an important role in type II diabetes, but it is not yet clear whether the described effect occurs causally or only as a side effect.

Given the effectiveness and efficiency of L-carnitine, on the one hand, and the negative effects of a manifest deficiency, on the other hand, the question naturally arises as to whether or not additional intake in the form of dietary supplements makes sense.

Supplementation is not necessary

Basically, there is no universal answer to this, but it can be said that healthy people who eat a balanced diet do not need any supplementation. This generally also applies to vegetarians, vegans, and pregnant and lactating mothers provided that none of the deficiency symptoms described above occur.

The situation is different in the case of a manifest deficiency with a cause related to a disease. In this case, it is sensible to make up for the deficit and it should also be done immediately. If the cause of the disease cannot be eliminated, a permanent intake is necessary.

In the case of temporary illnesses, the dose can be lowered slowly as health status improves so that the body can take over regulation again. Using preparations as a means to lose weight and as a fat burner is pointless according to current research.

A greater effect could not be scientifically demonstrated through a high-dose intake. The increase in the concentrations of the substance in the cell and the increase in the rate of fat burning could not be determined.

Tolerance and harmful effects of L-carnitine

Studies suggest that adverse effects may occur not only in the case of deficiency but also through increased intake of the substance over a longer period of time.

Scientists have determined that certain intestinal bacteria convert it to trimethylamine, regardless of the source of income, and then it is processed in the liver to produce trimethylamine N-oxide (TMAO). This substance is said to have a toxic effect on the artery walls and is therefore involved in the development of arteriosclerosis and subsequent diseases such as heart attack and stroke.

The consequences of these research results have not yet been clearly defined, because on the one hand there is this risky effect, but on the other hand, it is of vital importance for power generation. To make matters worse, there is still no reliable knowledge of where exactly the limit values ​​should be set for the ideal daily requirement.

Study experts advise against consuming too much L-carnitine. When it comes to diet, it is primarily about meat consumption. A principle here is not only to eat red meat less frequently but also to plan smaller portions.

The same applies to the intake of protein with food supplements in high doses. The fact that healthy people who eat a balanced diet do not need additional intake of synthetically manufactured preparations also speaks against this form of intake of active ingredients. Furthermore, high doses of ingested often cause gastrointestinal problems.

woman exercising with bands

What are the classic sources of L-carnitine?

The best source for L-carnitine is from red meat. For this reason, you should eat between 100 grams and 300 grams of meat every day.

Poultry or plant foods contain only fragments or are sometimes carnitine-free. Especially vegetarians or vegans often have the problem that natural sources cannot be used.

Other possible intakes are made through vitamins and iron. If the body receives too little carnitine, natural production decreases in the subsequent course. Cheese and dairy products are also classic sources of carnitine.

How is the dietary supplement taken?

L-carnitine is available as a dietary supplement in capsule, liquid, or powder form. Capsules sometimes have the advantage that they can be easily taken. There are also no major difficulties in terms of dosage.

The dosage is generally specified by the manufacturer. That may, depending on the manufacturer, be different from one to the other. It is important that the capsules are taken with enough water.

Powdered or liquid carnitine are other forms of nutritional supplements, which on the one hand are absorbed very quickly by the body, but on the other hand, are more complicated to dose.

It is advisable that the athlete take the dietary supplement around 30 minutes before training.

Take L-Carnitine 30 minutes before the start of training

There is no real recommendation on when to take L-carnitine. The manufacturer’s specifications also vary here. In theory, it can be taken at any time of the day. However, it makes sense if it is taken 30 minutes before training.

This sometimes ensures that the nutritional supplement is available when the body begins to break down carnitine and the body needs more replenishment. The daily dose of 5 grams should generally be met and never exceeded.

This is because otherwise, it increases the risk of side effects. The classic side effects of an overdose include vomiting or nausea. L-carnitine also ensures significant sweat production. For this reason, it is important that enough liquid is absorbed.


L-carnitine is a highly active chemical compound that plays a central role in carbohydrate and fat metabolism.

It is responsible for bringing long-chain fatty acids from cell plasma to the mitochondria, where they are used to generate energy. It also improves the effects of insulin by promoting glucose absorption in cells.

Both processes are life processes that, along with other metabolic activities, are vital to many physiological processes. A manifest deficiency means that the body cannot receive enough energy and is accompanied by a reduction in performance.

This can refer to the entire system or specifically to the muscles. Carnitine is synthesized by the body or can be absorbed through food. The exact need depends on various parameters and can fluctuate greatly.

How high it should really be, has not yet been clarified. Normally, the need is met through self-synthesis and food intake.

Furthermore, the system is highly adaptable, so problems rarely arise even with a low intake.

A manifest deficiency usually arises from a serious illness, genetic defects, actual malnutrition, or a sharp and rapid loss. In this case, the deficit must be compensated temporarily or permanently with adequate preparations. Otherwise, there is generally no reason to take dietary supplements in high doses, a balanced and conscious diet is sufficient.

This also applies to vegetarians, vegans, and pregnant and lactating women if none of the symptoms described are present. The scientific findings demonstrate in particular that the promises in the weight loss and fitness market have no verifiable basis.

Neither accumulation in cells nor increased fat burning could be demonstrated after ingestion.

In the best case, excess amounts are simply drained through the urine. However, they can also become toxic substances in the intestine that damage the artery walls.

Therefore, it is enough if you pay attention to a healthy and balanced diet. As long as you are comfortable and your performance and alertness are not restricted, no further action is necessary.

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