Generality
Creatine (from the Greek kreas = meat) is an amino acid derivative naturally present in our body.
In a 70 kg male subject, the amount of body creatine amounts to about 120g; this concentration increases as the subject's muscle mass increases.
Once synthesized or taken through the diet, creatine is picked up by the muscle tissue and stored there.
Phosphorylated in phosphocreatine, creatine is one of the muscular energy deposits. It is therefore used as needed during rapid and intense muscular contractions.
The human body consumes about 30 mg of creatine per kg of body weight per day, equal on average to 1.5 - 2% of its body reserves. The amount of creatine thus "degraded" is eliminated through the urine in the form of creatinine.
The amount of creatine needed to compensate for the losses obviously tends to increase in proportion to the muscle mass and the intensity of the exercise done.
Fortunately, an adequate diet is able to easily compensate for the amount consumed, thus satisfying even the most intense needs.
The daily requirement of creatine is therefore about 2 g (1.5% of 120 grams) and is satisfied through endogenous synthesis (1 gram / day) and through nutrition.
Meat and fish contain a fair amount, but a good percentage is lost during cooking. See: creatine content in food
Creatine introduced with the diet does not undergo changes during digestion and is incorporated mainly in skeletal muscle (95%), in free form (40%) and in the form of creatine phosphate or phosphocreatine (60%).
History of Creatine
The French chemist Michel Eugène Chevreul (Angers 1786-Paris 1889) isolated creatine from meat broth.
In 1847 Lieberg's studies confirmed that creatine was a normal constituent of meat.
In addition, Lieberg observed that the meat of wild foxes contained ten times more creatine than was found in the fox muscle kept in captivity; he came to the conclusion that motor activity tends to increase creatine muscle concentration.
Biological Functions
From a metabolic point of view, creatine intervenes to satisfy the energy demands of the anaerobic alactacid mechanism.
The anaerobic alactacid mechanism is that energetic mechanism that is activated as soon as an intense muscular effort begins. This process involves only one chemical reaction and allows for immediate availability of energy.
PC + ADP = C + ATP
where is it:
Oxygen is not used in this energy mechanism, which for this reason is called anaerobic.
The alattacid agent emphasizes instead that during the reaction there is no production of lactic acid.
As we have said, this system has a very short latency, a high power but a reduced capacity. It means that it activates quickly, generates large amounts of energy in the unit of time, but it runs out very quickly.
The phosphocreatine reserves, in fact, are exhausted within 4-5 seconds, even if the amount of creatine phosphate present in the muscles is variable and increases with training.
During intense muscular activity and very short duration, the decrease of the developed force is directly connected to the depletion of the phosphocreatine muscular reserves.
Indications
Why is creatine used? What is it for?
Creatine is widely used in sports as an ergogenic aid, although recent evidence has also characterized a very interesting antioxidant, cardioprotective and neuroprotective activity.
Creatine has also been used successfully in clinical settings, in the course of diseases such as muscular dystrophy, amyotrophic lateral sclerosis, sarcopenia, cachexia and heart failure.
Property and Effectiveness
What benefits has creatine shown during the studies?
Contrary to what one might think, especially in light of the very important biological role of creatine, the studies currently published in the literature show data that are still very contrasting with regards to the real utility of this supplement, both in sports and in clinical settings.
Creatine and sport
Most studies have clearly focused on the potential ergogenic role of creatine in exercises and sports with a high intensity of execution.
According to some authors, an appropriate supplementation protocol would guarantee:
- An appreciable increase in creatine muscle concentrations, in some cases by almost 20%;
- An improvement in contractile capacity and neuromuscular function;
- An increase in critical power, ie the maximum power exerted in an exercise before the feeling of fatigue is triggered;
- A reduction in the feeling of fatigue.
These data were collected under ideal "laboratory" conditions that are difficult to reproduce in a normal training session or in the competition.
To complicate the picture on the efficacy of creatine in sports, the results of some works would contribute, according to which, following a careful rereading of over 71 clinical trials published in the 90s, significant performance improvements would not emerge following the creatine intake.
Creatine and body composition
However, the so much coveted muscle increase linked to the intake of creatine, vaunted from various sources, would be a blunder, as it is the result of the increase in the content of intracellular liquids (as observed by impedance data).
Creatine and neuromuscular pathologies
Preliminary studies have tested the usefulness of creatine in the management of complex neuromuscular diseases, such as amyotrophic lateral sclerosis.
According to partial data, adequate creatine supplementation would seem to improve motor performance tests in affected patients.
The hypothesized mechanisms would see as protagonists both the ergogenic and the antioxidant activity of creatine.
Doses and method of use
How to use creatine
Over time, various protocols for taking creatine monohydrate have alternated, especially in sports.
From a careful examination of the scientific literature, the protocols currently most used in sports are two.
The first is the assumption:
- 20g of creatine per day (or 0.3 g per kg of body weight), divided into at least 4 daily administrations, for 2-5 days (loading phase);
- at the end of the loading phase, for the next 4 weeks take 2g of creatine per day (maintenance phase).
The second intake protocol consists of a daily intake of 3-6 g, without loading and maintenance phases.
According to some authors, the second protocol would guarantee in the long term the same effects as the first, in terms of improvement of high intensity anaerobic performance, with a lower risk of side effects, above all of gastro-enteric nature.
In both protocols, in order to optimize their bioavailability, creatine should be taken with simple sugars.
In light of some evidence, according to which the endogenous production of creatine and the capacity for muscle storage would be reduced during the use of creatine supplements, it is currently suggested to intersperse the periods of intake at rest phases of at least 4-6 weeks .
Creatine, Glucose and Protein
Studies carried out in recent years have shown that creatine absorption is increased by the simultaneous administration of carbohydrates with a high glycemic index, such as glucose.
Insulin is in fact able to increase the passage of creatine from the circulatory stream to the muscle cells. In order for the insulin response to be maximized, however, it is necessary to take about 20 grams of glucose per gram of creatine, which can be dangerous for those suffering from insulin resistance and type 2 diabetes.
Generally, the carbohydrate dose is taken about 30 minutes after that of creatine; in fact, it is necessary to create the glycemic peak when creatine has already been absorbed at an enteric level and is located in the bloodstream, ready for its entry into the cells. We then tried to add creatine supplements to other molecules that can increase insulin production, such as chromium picolinate, alpha lipoic acid and some amino acids.
However, little importance has been given to the fact that proteins are also able to increase insulin production. The simultaneous intake of creatine, glucose and protein could therefore be the most effective solution to ensure maximum creatine absorption.
Side effects
The side effects related to inadequate creatine intake can be of different clinical importance in terms of quantity or time.
More precisely, excessive use of creatine could lead to acute diarrhea, cramping abdominal pain, skin rash and allergy-like symptoms.
Prolonged use of creatine over time may induce:
- An increase in blood creatinine concentrations;
- Dehydration and alteration of arterial pressure;
- Weight increase;
- Muscle cramps;
- Myopathies.
Fortunately, the incidence of serious adverse reactions such as renal failure and atrial fibrillation is very rare.
When should creatine not be used?
The use of Creatine is contraindicated in dehydrated patients or patients with renal impairment (renal insufficiency, nephrotic syndrome, other renal diseases or predisposing conditions).
The aforementioned contraindications would also extend to subjects hypersensitive to the active ingredient.
Pharmacological Interactions
Which drugs or foods can modify the effect of creatine?
There are currently no known pharmacological interactions between creatine and other active ingredients.
However, in sports, the muscle bioavailability of creatine could be enhanced by the simultaneous intake of simple sugars.
Precautions for use
What do you need to know before taking creatine?
The use of creatine supplements should be avoided during pregnancy and lactation, in children and in all cases of increased risk for kidney disease.
For this reason, in certain cases it would be advisable, with your doctor, to monitor the degree of renal function before starting the use of creatine.
Following the use of creatine, especially at high doses, an increase in body weight may occur, mostly related to increased fluid retention.
Deepening Articles
Below, you will find links to the main articles of the site that deal with topics related to creatine :
Creatine in brief Creatine intake Creatine effects Creatine system - creatine phosphate Creatine use Creatine types Creatine monohydrateCreatine pureMicronized creatineNew forms of creatineCreatine and protein - creatine and insulin How much creatine Creatine in food Creatine and sport Creatine in food and urine of creatine
