Carnitine and exercise 🆙

Introduction

Before analyzing specifically the role of carnitine in motor exercise, the impact that a possible deficiency of this compound could exert and how to remedy it by integrating it into the diet, it is good to briefly summarize some essential notions about carnitine.

Carnitine is a derivative of the amino acid lysine; as such, it contains carbon, hydrogen, oxygen and nitrogen (C, H, O, N) and is mainly synthesized in the liver and kidney.
Its active form is L-carnitine.
It performs functions that are decisive for health and life, as:

It allows long-chain fatty acids to enter the mitochondria where they are oxidized to produce energy in the form of ATP (adenosine triphosphate) molecules.
Stabilizes the levels of acetyl-CoA and Coenzyme A in the mitochondria, releasing the residual acetyl from the oxidation processes (responsible for the production of ATP), thus preventing the toxic effect of any accumulation.

The human body concentrates carnitine above all where it is needed, therefore in the skeletal muscle and in the heart muscle (heart).
It can be obtained from foods, especially of animal origin, and in particular from red meat and offal.
Endogenous biosynthesis (ie the autonomous production of the organism) is the result of a series of enzymatic reactions; not all organs are capable of performing it completely.
Generally it is not an essential nutrient because, under normal conditions, it is produced by the body; however, there are transient conditions, special situations or other causes that can lead to a deficiency or decrease in carnitine levels.
In genetic diseases, carnitine deficiency has very serious effects on heart health and beyond.
Carnitine has been proposed and tested, in its various chemical forms (L-carnitine, Acetyl-L-Carnitine and Propionyl-L-Carnitine), for the treatment of central nervous complications, cardiac, degenerative diseases of the central nervous system, chronic fatigue and not only.
Carnitine and its esterified forms (Acetyl-L-Carnitine and Propionyl-L-Carnitine) are included in the composition of both real drugs and food supplements. Carnitine-based medicines are used for the treatment of pathological forms of deficiency. As a food supplement, on the other hand, carnitine is used in sports supplements as a molecule with an ergogenic power for endurance disciplines and as a remedy to combat asthenia, fatigue and physical and mental fatigue.

Let us now try to understand how carnitine is essential for energy production (adenosine triphosphate - ATP).

Fat, Carnitine and ATP

Fatty acids: digestion, absorption and transport

The energy necessary for cellular and metabolic processes (which are the essential basis of any bodily function) is stored and released by a molecule called adenosine triphosphate or ATP (from the English Adenosine TriPhosphate). This energy is contained in the bonds between the three phosphate groups (PO4-) and adenosine, which are established at the end of a complex series of reactions, at the basis of which the oxidation of energy nutrients (proteins, carbohydrates and fats) takes place. .

The famous "calories" of food correspond to the sum of the energy potentially obtainable from the oxidation of:

Protein amino acids (4 kcal / g);
Carbohydrates (3,75 kcal / g);
Fats or lipids (9 kcal / g).

The lipids, therefore, are the macromolecules that allow us to produce more calories - not surprisingly they represent the reserve substrate of our organism (fats of adipose tissue). In nature, fatty acids are grouped into triglycerides (glycerol + 3 fatty acids); as this protects them from degeneration and makes them more convenient for storage and transport.

Dietary fats must first be digested (through the action of saliva, biliary emulsion and pancreatic / intestinal enzymatic lysis) and subsequently absorbed in the small intestine. The short-chain ones end up directly in the blood, while the medium and long ones end up in the lymphatic circulation. Simply speaking, almost all lipids are transported in the lymph and blood, up to the target cells, by special transporters called lipoproteins (chylomicrons, VLDL, LDL, IDL and HDL).

Importance of carnitine and mitochondria in ATP production

The fatty acids are mainly destined to the cells of the muscle tissue, where they are used for the production of calories, or to the adipose tissue, where they are stored again in reserve triglycerides.

Contrary to carbohydrates, which can produce small amounts of energy even in the absence of oxygen, fatty acids must be oxidized within the mitochondria (beta-oxidation process of fatty acids), therefore, the presence of oxygen is essential.

This is where carnitine comes into play which, by binding long-chain fatty acids and allowing them to pass through the membrane, is the only means of transport for these nutrients within the mitochondria matrix.

It is essential to underline how important mitochondrial oxidation is for life, for health and for the efficiency of our organism; fatty acids in particular, offer a greater metabolic contribution during muscle activity.

Carnitine is therefore also indispensable in physical exercise and sports performance, especially aerobic and prolonged ones.

Detoxification process

Another non-negligible property of carnitine is that of detoxification.

As mentioned, in fact, thanks to its mechanism of action, carnitine is able to prevent the accumulation of acetyl groups and acyl groups within the mitochondrion that are generated following the beta-oxidation processes of fatty acids. In fact, if these groups were not removed, they would accumulate inside the mitochondrion, exerting a toxic action.

This task too - together with the production of energy - is of fundamental importance during physical motor activity.

Carnitine deficiency: causes and symptoms

When we talk about carnitine deficiency we refer to a series of pathological conditions characterized by drastically low levels of this precious molecule. Carnitine deficiencies or deficiencies can be divided into:

Primary carnitine deficiency, caused by mutations affecting genes coding for proteins involved in what is called the carnitine system (the latter is the set of reactions that allow carnitine to carry out its task and which see the involvement not only of this amino acid derivative, but also of its derivatives, proteins and specific transporters localized on the cellular and mitochondrial membrane);
Secondary carnitine deficiencies which may be due to:

Increased need (can occur in case of sepsis or serious infections, following surgery, etc.);
Reduced intake (occurrence that can occur when following incorrect or inadequate diets, when subjected to prolonged parenteral nutrition for long periods, etc.);
Excessive loss (can be induced by taking certain types of drugs, excessive diarrhea, hemodialysis, etc.);
Reduced synthesis induced by pathologies affecting the kidneys and liver (for example, cirrhosis, renal insufficiency, etc.).

The symptomatology and its onset can vary according to the type of deficit considered and according to the severity of the disease. However, both types of deficiency have some common symptoms, such as:

Muscle weakness and fatigue;
Accumulation of lipids in the heart, muscles and liver;
Cardiomyopathy;
epatopathy;
Renal and nervous system disorders.

In more serious cases, moreover, even death can occur.

As can be seen, regardless of the triggering cause, when carnitine is deficient in the body, muscle strength is compromised and fatigue and weakness develop. Carnitine, in fact, is concentrated above all (but not exclusively) at the level of the muscles where it plays its fundamental role in the production of energy. Its lack or insufficiency does not allow adequate transport of fatty acids within the mitochondrion, consequently, they cannot be oxidized and the production of ATP - therefore, of energy - does not occur. Lacking the main source of energy, cells are unable to carry out the processes that guarantee their functioning and survival, therefore, tissues and organs are affected.

Treatment

The treatment of carnitine deficiency involves the administration of medicines based on L-carnitine or its esters (acetyl-L-carnitine, propionyl-L-carnitine) orally, or intravenously, as appropriate. In these situations, the intervention of the doctor is always necessary.

Physical Fatigue and Carnitine

Given the indispensable task performed by carnitine in the production of energy at the level of the mitochondrion, many studies have been carried out on this amino acid derivative to better understand its properties and biological roles. From some of these, it emerged that in some particular conditions (for example, during convalescence, during aging, etc.) there may be a decrease or insufficiency of carnitine levels which, however, do not manifest themselves at drastic and pathological levels. like those described above.

In particular, the onset of fatigue, physical fatigue, reduction in muscle mass and even mental fatigue have been associated with the reduction in carnitine levels. In these cases, supplementation with L-carnitine or its esters (acetyl-L-carnitine and propionyl-L-carnitine) has been proposed as a possible remedy. In this regard, we cite some studies conducted on this use of carnitine and its esterified forms which have shown how:

The administration of L-carnitine in convalescent children at a dose of 500-1000 mg per day may lead to an increase in appetite and a reduction in asthenia.
The administration of L-carnitine in elderly patients at a dosage of 2 grams per day for one month led to an increase in muscle mass and a reduction of about 40% of both physical and mental fatigue.
The administration of proprionyl-L-carnitine in elderly individuals at a dose of 2 grams per day for a period of 24 weeks led to an improvement in the patient's well-being and a reduction in physical and mental fatigue.

Exercise and Carnitine

In light of the importance of carnitine in the processes that lead to the production of energy in the muscles, several studies have been carried out to investigate its potential applications in physical exercise and sports.

In this regard, we cite a study conducted on elderly patients which showed that the administration of carnitine at a dose of 1,5 grams per day for a period of 10 weeks can lead to an increase in muscle strength and a reduction in frailty.

The proposals for integrating carnitine in sports are justified by the fact that - given its ability to optimize the use of fatty acids to produce energy and detoxify the mitochondrion from waste deriving from the beta-oxidation process - its use may be useful. to improve muscular endurance and athletic performance and to promote recovery.

A study conducted on healthy volunteers during progressive training (triathlon) showed that the administration of carnitine at a dosage of 2 grams per day for 24 weeks was able to produce an improvement in physical performance in individuals who took the amino acid derivative. in question compared to those who took the placebo.

To be fair, however, it should be noted that the effectiveness deriving from the use of carnitine in sports is, in reality, the subject of debate. If on the one hand, in fact, there are studies that confirm its usefulness; on the other hand, some studies do not agree with what has just been stated.