Creatine: The chemistry behind the supplement

A look at the science behind the world's most popular supplement. And a detailed look at creatine from a chemical and biochemical point of view.

Introduction

Creatine has a very long and controversial history. Creatine (methyl-guandinoacetic acid) was discovered by French scientist Michel Eugene Chevreul in 1832. Chevreul was studying the various metabolic products found in meat when he first isolated creatine. He named it after the Greek word for meat, kreas (16). What Chevreul did not know at the time, of course, was that creatine would one day become the most popular dietary supplement in the world (1).

Justus von Liebig confirmed Chevreul's discovery in 1847 and carried out additional research into creatine and animal physiology. Liebig made several interesting discoveries during his investigations. He found that wild foxes had ten times more creatine in their skeletal muscles than foxes kept in captivity. He concluded from this that physical training leads to an increase in the concentration of creatine in skeletal muscle (1).

In 1927, phosphocreatine - a derivative of creatine - was discovered. This groundbreaking discovery was made by Fiske and Subbarow (1). Their research established the fact that phosphocreatine concentrations in skeletal muscle decrease during muscle contractions and increase again during rest (1). They also discovered the (important?) role that phosphocreatine plays in energy production.

After these discoveries by Fiske and Subbaro, not much more research was done with creatine until 1992, when Chanutin reported that total creatine concentrations in skeletal muscle increased after creatine supplementation (1). This discovery meant that supplemented creatine can be directly absorbed into skeletal muscle.

This study was confirmed by other studies, including one conducted by Harris et al in 1992, which is considered to be the study that started the creatine supplementation revolution (17). As a result of the Harris et al study, the number of studies conducted with creatine skyrocketed.

The purpose of this article is to show how creatine can be used as a sports supplement from a chemical standpoint and to examine different factors that may contribute to the effectiveness of creatine supplementation.

Over the last few years, creatine has become an interesting topic outside the field of sports performance enhancement and has also found its way into the medical field. There is evidence that creatine may play a role in the treatment of various disorders and diseases such as Parkinson's disease, neuromuscular diseases, brain diseases, muscular dystrophy and even heart disease (2, 19). This evidence has paved the way for the potential use of creatine outside of the athletic arena.

Creatine in the human body

As mentioned above, phosphocreatine concentrations have been shown to fluctuate during muscle contractions (19). This suggests the role that creatine plays in the human body. It has been speculated that creatine may ultimately increase the amount of energy that people "store" within their skeletal muscles. When a muscle contracts, it uses the hydrolysis of a phosphoanhydride bond of an adenosine triphosphate (ATP) molecule to release energy.

The hydrolysis of the ATP molecule leads to the formation of an adenosine diphosphate (ADP) molecule (3). This is the primary mechanism used by the human body to obtain energy during muscle contractions. Because of this reliance on ATP hydrolysis, the concentration and consequently the availability of ATP in skeletal muscle is critical in determining the amount of energy a muscle has available to perform contractions (e.g. during exercise).

It is important to note that when ATP is dephosphorylated to ADP, ATP resynthesis also occurs within the muscle tissue at the same time. This is the point at which creatine becomes a crucial factor in the energy production of muscle cells in the body. During muscle contractions, this resynthesis of ATP from ADP is achieved by a breakdown of phosphocreatine. This reaction can be seen in Figure 1 (4):

Figure 1: The creatine kinase reaction depicted on this graph is the creatine kinase reaction that occurs within skeletal muscle to allow ATP resynthesis. As you can see, phosphocreatine in combination with ATP creatine (Cr) and ATP provides ATP that can be used for energy production.

Source: Wyss and Kaddurah-Daouk (2000). (4)

As a result of this direct reaction between phosphocreatine and ADP, phosphocreatine concentrations are the limiting factor for ATP resynthesis. With this knowledge of how skeletal muscle utilizes the creatine kinase reaction to produce energy, we can now further investigate the effects of creatine supplementation. Many factors related to creatine supplementation, as well as the effectiveness of creatine supplementation in enhancing performance, are described below.

The first factor to examine is the contribution of creatine in its pure form to maintaining energy levels. Although creatine does not react directly with ADP to produce ATP, there is a pathway by which creatine supports the resynthesis of ATP, as shown in Figure 1. Creatine fulfills this role by acting as a buffer for the reaction that occurs during the resynthesis of ATP (5).

It has been shown that the total concentration of phosphocreatine in skeletal muscle increases after creatine supplementation (6). Therefore, creatine supplementation prevents the phosphocreatine concentration from decreasing to such an extent that the balance shifts away from ATP production. The increased phosphocreatine concentration also shifts the balance towards ATP production. In turn, this buffer system allows faster and more efficient production of ATP, which results in an increase in the overall availability of ATP.

However, while many would like to think of creatine as the perfect supplement for energy production in muscle tissue, reduced energy production is not the only reason muscle fibers become fatigued. The other factor to consider when it comes to muscle fatigue is the accumulation of lactate (lactic acid) during muscle contractions. When a muscle contracts, the demand for ATP begins to increase. As the consumption of ATP increases, lactic acid is produced in the muscle faster than it can be removed, causing the concentration of lactic acid in the muscle tissue to rise.

Increasing lactate concentrations lower the pH in the muscle, which has been identified as the cause of a fatiguing effect in the muscle (7). However, it is important to note that according to Katz et al, fatigue that occurs during short-term contractions is more strongly related to low phosphocreatine levels than to an increase in lactic acid concentrations (8). This result was confirmed by Saugen et al (18). These results demonstrate the important role that phosphocreatine plays in the amount of energy a muscle can produce during contractions.

Another aspect of creatine in the human body that needs to be considered is which types of muscle fibers use more creatine during their contractions. According to Casey and Greenhaff, the two types of muscle fibers found in skeletal muscle - type I and type II - use creatine in different amounts (3). Type I muscle fibers, also known as slow-contracting fibers, are more useful during endurance activities such as long-distance running and cycling, while type II muscle fibers, also known as fast-contracting muscle fibers, are primarily used for short maximal muscle efforts such as weight training.

Casey and Greenhaff report that the use of phosphocreatine in type II fibers can be up to 33% higher than in type I fibers. Since the primary energy source for type I muscle fibers is triglycerides (fatty acids) and type II muscle fibers primarily use ATP, it can be speculated that creatine supplementation will be more useful for short explosive anaerobic activities such as moving weights and sprinting than for prolonged aerobic exercise (3).

It is also important to examine the maximum amount of creatine, and ultimately phosphocreatine, that can be stored within muscle fibers. The average person consuming a normal diet consisting of protein, carbohydrate and fat will provide an approximate baseline creatine level of 120mmol creatine per kilogram of lean body mass (5). This amount can also be substantially lower depending on the individual diet. Vegetarians, for example, have lower creatine levels due to the absence of meat in their diet.

According to Paddon-Jones et al, the maximum skeletal muscle concentration that can be achieved through supplementation is 160mmol per kilogram of lean body mass (5). This concentration cannot be further increased by additional creatine supplementation. Once this concentration has been reached, any additional creatine consumed is simply excreted.

In addition to the proposed energetic effects that creatine has on skeletal muscle, creatine has also been shown to play a role in the mechanism that controls muscle protein synthesis. In one study, scientists found that increased concentrations of creatine within skeletal muscle cells led to increased synthesis of myosin heavy chains (9). These studies were conducted in vitro using tissue cultures. The results of the study by Ingwall et al are shown in Table 1.

	Experiment #	Total protein synthesis (cmp/ g DNA)	Synthesis of myosin heavy chains (cmp/ g DNA)	Increase in the rate of myosin synthesis in %
Control group	1	149,000	360	-
	2	134,000	350	-
+5mM Creatine	1	161,000	800	120
	2	151,000	610	75

Table 1: Total percentage of myosin heavy chain synthesis after creatine supplementation in tissue cell cultures. The cell cultures were incubated for 4 hours during which a 5mM creatine solution or warm water was added. As can be seen, the amount of myosin heavy chains increased dramatically after the addition of creatine to the cell cultures. Total protein synthesis and total myosin heavy chain synthesis were determined using 3H decay analysis (9).

As can be seen, the increase in creatine concentrations increased the amount of myosin heavy chains and the total amount of protein produced within the cell. These results were later confirmed by similar studies by Ingwall et al (19). Because myosin heavy chains are the primary protein that initiates muscle contraction, these results suggest that creatine promotes maximal muscle contraction via two distinct mechanisms: an energetic effect and a promotion of myosin heavy chain synthesis.

In turn, however, it is also important to note that some studies were unable to show that creatine supplementation increases total protein synthesis. However, one of these studies was able to show that creatine supplementation could potentially reduce the rate of protein catabolism, where protein is broken down in the body (19).

Although the theoretical possibilities of creatine seem amazing, the question remains whether creatine supplementation can enhance athletic performance. There have been countless studies regarding creatine supplementation that have come to contradictory results [, something is missing from verb] . Casey and Greenhaff found that his creatine supplementation with 20 grams of creatine per day for 5 days resulted in increased maximal isokinetic leg extension performance by up to 4% (3). Casey et al discovered that with the same supplementation program as Casey and Greenhaff, nine male subjects were able to increase their work performed during several maximal isokinetic exercises by an average of 4% (10).

Harris et al conducted tests with trained middle-distance runners at Tartu University, where they found that creatine supplementation of 20 to 30 grams per day for five days improved the runners' times in their respective runs compared to a placebo group (11). This study, conducted by Harris et al, suggested that creatine is not only useful for short-term maximal muscle contractions, but may also be beneficial in athletic activities such as mid-stretch runs, during which more type I muscle fibers are used.

Although a large number of studies have been conducted showing that creatine supplementation can improve athletic performance, there are many other studies that have failed to find such evidence. One such study, which examined the performance of rowers, was conducted by Syrotuik et al (12). The study was unable to find any significant differences between the subjects who supplemented creatine and the placebo group over the eight-week study period. Similar results were observed by Odland et al during 30 seconds of maximal exercise (13).

Since many of these studies seem to contradict each other, it is important to look at some of the aspects of the studies mentioned above. The study conducted by Odland et al only lasted for three days and many believe that this period is too short to achieve a sufficient increase in phosphocreatine levels within the muscles. The normal period required to achieve a maximum increase in creatine concentrations within the muscles and to maintain these concentrations is 5 days of creatine supplementation. The shortened duration used in this study may have led to inaccurate results and conclusions.

The study conducted by Syrotuik et al lasted significantly longer than the study just mentioned. However, this study used the same training volume for the supplement group and the placebo group. When phosphocreatine levels increased in the supplement group, these subjects were unable to increase their training volume when they wanted to. As the training volume was kept constant in both groups of the study, this could have led to inaccurate results.

Based on the above results, the question of the effectiveness of creatine supplementation is still open. However, it is important to note that of the 300 studies examined by Kreider as part of a meta-study, approximately 70% reported clearly noticeable positive effects of creatine supplementation (20). Despite the fact that the majority of these studies concluded that creatine supplementation enhances athletic performance, it is still important to consider the different types of creatine that are commercially available. Some of the more popular creatine derivatives are discussed in more detail in the following section.

Creatine derivatives

Creatine monohydrate was the first form of creatine to be sold as a dietary supplement (15). Creatine monohydrate consists of a creatine molecule bound to a single water molecule (hydrate). This is the simplest and most popular form of creatine sold. Creatine monohydrate has a controversial history in terms of its bioavailability and effectiveness as a supplement. Many believe that creatine monohydrate cannot pass through the gut with great efficiency and therefore has low bioavailability (4).

For this reason, it is often recommended that creatine monohydrate should be consumed in conjunction with simple carbohydrates to induce an insulin release, which is believed to increase the absorption of creatine (3). However, although this is a widely held belief, Harris et al conclude that the bioavailability of creatine monohydrate is around 100% (14).

Another reason that creatine monohydrate is controversial is that it has poor solubility in water at room temperature, around 14 grams per liter of water (15). This poor solubility makes it necessary for creatine to be mixed with a large amount of warm water to produce a consistent, uniform solution (15).

Another factor to consider with the different creatine derivatives is the rate at which creatine derivatives are broken down into creatinine once they reach the bloodstream. Harris et al conducted a study that investigated how three different types of creatine (creatine monohydrate, creatine citrate and creatine pyruvate) affect creatine blood concentrations (14). They found that the different types of creatine resulted in different creatine blood concentrations during a certain period of time after supplementation. The results are shown in Table 2.

	Creatine Monohydrate	Creatine citrate Citrate	Creatine pyruvate
Time (h)	Mean concentration (M)	Average concentration (M)	Average concentration (M)
0.0	40.5	56.5	44.0
0.5	488.6	551.1	637.0
1.0	761.9	855.3	972.2
1.5	660.8	771.8	875.7
2.0	557.0	624.2	681.7

Table 2: Blood creatine concentrations after consumption of different forms of creatine. Three men and three women supplemented with the different forms of creatine, which were administered in the form of capsules. Each subject was given all three forms of creatine in turn. The amounts administered were 5 grams of creatine monohydrate, 6.7 grams of creatine citrate, and 7.3 grams of creatine pyruvate. The different amounts were used to ensure that each subject consumed exactly 5 grams of pure creatine with each administration. As can be seen, the different forms of creatine produced different results (14).

Since creatine monohydrate was shown to have a bioavailability of approximately 100%, the scientists speculated that the differences in blood concentrations were the result of a different rate of degradation of the different creatine derivatives (14).

The reasons for these different results lie in the molecular structure of the different derivatives of creatine. Creatine citrate is more soluble in water than creatine monohydrate, which makes it easier to achieve more consistent supplementation when taken orally. Creatine citrate is in the form of a salt in which a creatine molecule is ionically bound to a citric acid molecule. This form of creatine has a lower pH value of around 5 due to the citric acid molecule. This slightly increases the bioavailability and reduces the rate at which creatine is broken down.

The latter is related to the fact that acidic creatine is more stable in the acidic environment of the stomach (15). Creatine pyruvate is very similar to creatine citrate in that it is present as a salt of creatine and pyruvic acid (15). This modification also reduces the pH of the creatine molecule, thereby slightly increasing its bioavailability, improving water solubility and slightly reducing the rate of degradation to creatinine.

Another popular form of creatine is creatine ethyl ester (CEE). CEE is a creatine-based compound in which the caroxylic acid end (do you mean carboxylic acid end?) has been replaced by an ethyl ester (2). Because creatine is broken down into creatinine faster than the ethyl ester derivative in the acidic environment of the stomach, the bioavailability of CEE is slightly higher than the monohydrate form (2). This slower breakdown of CEE allows the body to utilize the full amount of creatine consumed. In addition, CEE has a higher lipophilicity, which results in better membrane permeability (2). This allows the CEE molecule to enter the muscle fibers more easily and efficiently than creatine monohydrate.

Conclusion

It's easy to see why creatine has such a controversial history. The many different factors that determine creatine's efficiency vary from person to person. However, it is also easy to see why creatine has become the most popular supplement in the world (1). It was reported that at the 1996 Olympics, nearly 80% of athletes supplemented with creatine (5).

The theoretical possibilities for creatine are astounding, but it is still very difficult to draw a definitive conclusion regarding the effectiveness of creatine. As mentioned above, 70% of 300 studies concluded that creatine supplementation can increase athletic performance within a surprisingly short period of time, usually in the range of one week (20).

However, questions remain as to why the other 30% of studies were unable to show an increase in athletic performance through creatine supplementation. Although the majority of studies conducted found creatine to be effective, it is ultimately up to each athlete to determine whether creatine supplementation can improve their athletic performance.

References:

1. Bahrke, M.; Yesalis, C.; Creatine As an Ergogenic Supplement, Ch. 15. Performance-Enhancing Substances in Sports and Exercise, 1st edition; Human Kinetics: Champaign, Illinois, 2002; 175-209.
2. Vennerstrom, J. L. Production of Creatine Esters Using In Situ Acid Production. U.S. Patent 20050049428, August 25, 2003.
3. Casey, A.; Greenhaff, P. Does Dietary Creatine Supplementation Play a Role in Skeletal Muscle Metabolism and Performance?. Am. J. Clin. Nutr., 2000, 72, 607-617.
4. Kaddurah-Daouk, C; Wyss, S. Creatine and Creatinine Metabolism. Physiol. Rev, 2000, 80, 1107-1213.
5. Paddon-Jones, D et al. Potential Ergogenic Effects of Arginine and Creatine Supplementation. J. Nutr,, 2004, 134, 2888-2894.
6. Parise G. et al. Effects of Acute Creatine Monohydrate Supplementation on Leucine Kinetics and Mixed-Muscle Protein Synthesis. J. Appl. Physiol., 2001, 91, 1041-1047.
7. Matsurra, R. et al. Effect of Blood Lactate Concentration and the Level of Oxygen Uptake Immediately Before a Cycling Sprint on Neuromuscular Activation During Repeated Cycling Sprints. J. Physiol. Anthropol., 2006, 25, 267-273.
8. Katz, A. et al. Muscle ATP Turnover Rate During Isometric Contraction in Humans. J. Appl. Physiol., 1986, 60, 1839-1842.
9. Ingwall, J. et al. Specificity of Creatine in the Control of Muscle Protein Synthesis. J. Cell Biol., 1974, 63, 145-151.
10. Casey, A. et al. Creatine Ingestion Favorably Affects Performance and Muscle Metabolism During Maximal Exercise in Humans. Am. J. Physiol., 1996, 271, 31-37
11. Harris, R. et al. The Effect of Oral Creatine Supplementation on Running Performance During Maximal Short Term Exercise in Man. J. Physiol., 1993, 467, 74P.
12. Syrotuik, R. et al. Effects of Creatine Monohydrate Supplementation During Combined Strength and High Intensity Rowing Training on Performance. Can. J. Appl. Physiol., 2001, 26, 527-542.
13. Odland, B. et al. Effect of Oral Creatine Supplementation on Muscle [PCr] and Short-term Maximum Power Output. Med. Sci. Spts. Exr., 1997, 29, 216-219
14. Harris, R. et al. Comparison of New Forms of Creatine in Raising Plasma Creatine Levels. J Int Soc Spts. Nutr., 2007, 4, 17-22.
15. Carnazzo, J. Method for Enhancing Delivery and Uniformity of Concentration of Cellular Creatine. U.S. Patent 5925378, July 20, 1999.
16. Tokish, J. et al. Ergogenic Aids: A Review of Basic Science, Performance, Side Effects, and Status in Sports. Am. J. Spts, 2004, 32, 1543-1553.
17. Harrise, R. et al. Elevation of Creatine in Resting and Exercising Muscle of Normal Subjects by Creatine Supplementation. Clin. Sci. (London), 1992, 83, 367-374.
18. Saugen, E. et al. Dissociation Between Metabolic and Contractile Responses During Intermittent Isometric Exercise in Man. Exp. Physio.l, 1997, 82,213-226.
19. Persky, A. Brazeau, G. Clinical Pharmacology of the Dietary Supplement Creatine Monohydrate. Pharmac. Rev, 2001, 53, 161-176.
20. Kreider, R. Effects of Creatine Supplementation on Performance and Training Adaptation. Mol. Cell. Biochem. 2003, 244, 89-94.

Source: https://www.muscleandstrength.com/articles/creatine-the-chemistry-behind-the-supplement.html