- What is creatine?
- How does creatine work?
- What are natural sources of creatine?
- How does creatine get into muscle?
- Do all muscles respond to creatine?
- Does everyone respond to creatine?
Creatine is, and always has been, a natural component of skeletal muscle. The only reason that creatine may seem like something new is a recent boom in scientific research in the area since the early 1990s. In a sense, creatine was rediscovered when world-class athletes became wise to the option of utilizing it to enhance their physical performance.
In truth, however, creatine was identified as an indispensable part of skeletal muscle some time ago. Nearly two centuries ago (1835) a French scientist and philosopher named Michel-Eugène Chevreul isolated a component from skeletal muscle that he gave the name Creatine after the Greek word for flesh, or Kreas. A few years later (1847) a German scientist named Justus von Liebig proposed that creatine is necessary to support muscular activity when he observed that wild (active) foxes contain more intramuscular creatine than foxes kept in captivity. Liebig later went as far as lending his name to a commercial extract of meat that he asserted would help the body perform extra “work“. Indeed, Liebig’s “Fleisch Extrakt ” could reasonably be considered the original creatine supplement – complete with marketing strategy.
In fact, meat and fish are the richest natural sources of creatine. Carnivores therefore, receive their creatine directly via dietary channels. Conversely, herbivores (and strict vegetarians), since they abstain from consuming these sources of creatine, are solely reliant on their body’s natural ability to synthesis creatine from basic components. Omnivores, on the other hand, have at their disposal both avenues from which to fulfill their daily creatine requirement.
When dietary creatine intake is restricted (or entirely absent) the body can produce creatine from amino acids made available during the digestion of foods (see “What are natural sources of creatine?“).Therefore, in one way or another, creatine is acquired from our diets. The production of new creatine (synthesis) principally takes place in the liver and kidneys, although the pancreas also contributes some to the body’s new synthesis of creatine. Creatine is produced in a chemical reaction involving three amino acids, arginine, glycine and methionine. Of these three, the requirement for dietary methionine is most critical, since the body does not readily produce it from starting materials (see “What are natural sources of creatine?“).
Although creatine is present in most cell types to varying degrees, the greater part of the body’s entire creatine reserve (95%) is found within skeletal muscle. The remainder (~5%) is principally found within the heart, brain and testes. These are all tissues with extremely high energy expenditures. Following ingestion (or synthesis) creatine is transported to our muscles where it serves to increase muscle energy levels (see “How does creatine get into muscle?“). Creatine achieves this by increasing the availability of ATP, the cell’s energy molecule (see “How does creatine work?“). The chemical reaction that produces creatine in the liver, kidneys and pancreas can be viewed here.
To become physiologically active creatine must first be enzymatically transformed into another molecule known as phosphocreatine (PCr). PCr is nothing more than a molecule of creatine that has been modified with the covalent attachment of a phosphate group. On average the body goes through about 2 grams of creatine (creatine and PCr) each day through a process of spontaneous degradation. This entails the spontaneous conversion of creatine and PCr into an energetically inert molecule known as creatinine. We typically notice an improvement in exercise performance when our muscle creatine levels increase by at least 20% as a result of creatine supplementation (see “Does everyone respond to creatine?“).
It is now common to supplement one’s diet with synthetically produced creatine in hopes of enhancing athletic performance. Synthetic creatine is sold as citrate, phosphate or monohydrate salts. Creatine monohydrate is the most commonly used form in athletics and is nothing more than a molecule of creatine accompanied by a molecule of water. A gram of creatine monohydrate also contains more creatine than a gram of either creatine citrate or a gram of creatine phosphate. You therefore consume less creatine monohydrate powder to get the same amount of active creatine.
The qualitative differences between natural and synthetic sources of creatine are discussed in Creatine: A practical guide.
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