A Narrative Review On Athletic Performance And Safety Of Creatine Supplementation For Adolescents

ABSTRACT

Creatine is an organic nitrogenous compound that can be obtained from the diet or produced by the body. It has been widely used and tested in laboratories mainly on adults. There are few studies aimed at adolescents (classified hesre as between 13 and 18 years old), but the studies point to promising results in improving performance and safety for the health of adolescents. Therefore, the purpose of this review is to contribute to the evidence-based discussion on the use of this supplement for adolescents.

KEYWORDS

Creatine; Sports nutrition; Sports medicine; Health; Performance

INTRODUCTION

Despite being an endogenously produced nutrient found in meat, chicken, and fish, creatine is regarded as one of the more consumed, researched, and efficacious nutritional supplements available (Figure 1); [1]. When supplemented occurs increases in intramuscular creatine stores and can improve effort capacity and training adaptations. Creatine has been established as a legitimate nutritional adjunct in rehabilitation.

Creatine is naturally found primarily in the flesh of animals, with the majority (~95%) being present in skeletal muscle. Approximately two-thirds of intramuscular creatine is phosphorylated (phosphocreatine-CrP). Metabolism of creatine results in 1-2% creatinine production and it being excreted via kidneys (Figure 2). The process of lost creatine leads to a daily ~2 g of creatine required per day to maintain normal creatine cells concentration. The human diet provides approximately half of this amount. The remaining amount of the total rate of appearance is provided by endogenous synthesis by the kidney and liver [2], 2000; [1].

Creatine is stored within the skeletal muscle as both free creatine and as phosphocreatine serving as a key substrate for the resynthesis of ATP [3]. It mainly serves as a critical metabolic intermediary of energy transfer by facilitating the recycling of ATP, the source of energy for use and storage at the cellular level. Consequently, creatine is abundant in organs with high energy turnover, with ∼95% of the human body’s creatine stores found in the skeletal muscle and the remaining 5% in the brain, liver, kidney, and testes (muscle or brain maintain a total cellular Cr pool of up to 30-40 mM) [4].

DISCUSSION

Supplementation

It is described that exogenous supplementation of creatine is an effective strategy to increase intramuscular (and other tissue) phosphocreatine stores by ~20-40% [1] depending on baseline levels. There are 3 ways, with slight variations, to supplement creatine. The first way, known as loading, is to supplement 3.0 grams per kilogram of body weight per day. To avoid intestinal discomfort, this dose is usually divided into 4 times distributed throughout the day. This strategy lasts from 3 to 7 days, which would be enough to saturate the cells [5].

The second supplementation strategy, called maintenance, consists of ingesting 0.3g of creatine per kilogram of body weight per day. It is normally ingested at a single moment of the day and usually takes more than 14 days to saturate the cells, and can be prolonged for weeks or months [5]; [1].

The last strategy would be a mixture of the two previous ones, in which the person would start with the loading dose for 3 to 7 days (3.0g per kg of weight) and persist using the maintenance dose (0.3 grams per kg of body weight) on subsequent days [5]; [1]. A summary can be seen in Figure 3. When supplementation ceases, it may take as long as 28 days before intramuscular CrP levels return to baseline [6,7]. It is not uncommon to use creatine “cycles”, in these cases the athlete uses creatine for 28 days, does a washout for 28 days, and then returns to use, returning to washout and supplementation. Despite having some popularity, the cycle strategy lacks a scientific basis. In addition, many manufacturers and professionals recommend supplementation 30 minutes before training, which is another strategy that is not based on nutritional and pharmacological fundamentals [8].

Efficacy of Creatine as an Ergogenic Aid

It has been widely demonstrated that the loading strategy, as described above, is very effective for significant increases in strength, power, and speed. [9-12]. It is essential to emphasize that gains only happen when accompanied by resistance, strength, or power training. Creatine does not present results per se and must be accompanied by efficient planning in training strategies Branch [13,14]. These outcomes are consistently reported across genders as well as in adolescents [15-33].

In addition, [11] found that a 20g per day for seven days of oral creatine monohydrate supplementation improved results in some cognitive tasks in mountain bikers. These findings show that creatine supplementation could be used for diminished mental fatigue in mountain bikers, potentially contributing to greater reaction times and better decision-making on the track.

Safety of Creatine Use

A growing number of studies are available that support the safety of creatine supplementation, unfortunately, the majority in adults. These studies have been conducted in both athletic and general populations and range from a few days up to to 5 years without any adverse changes in markers of clinical health [34]; [13]; [35,36]. Creatine supplementation has been demonstrated no adverse impact on clinical health markers in competitive athletes [13]; [37-46] and in clinical populations [47-50].

Recently, two studies evaluating over 40 biochemical and hematological health markers have shown that creatine supplementation is safe in young. Both studies revealed no significant changes in adverse outcomes following either 7 days [12] or 28 days [12] of creatine supplementation. The result of increased body mass as a side effect is practically unanimous, however, this increase is notorious for lean mass, not being an undesirable effect for most modalities in which creatine has been recommended (strength athletes, power athletes, bodybuilders, and clinical patients with muscle wasting disorders [1].

In addition, [51] helps us to unravel why many professionals are wrong when giving diagnoses about kidney health. By increasing creatine intake (supplementation), we naturally produce more creatinine, which is used to assess kidney health. In Figure 4 we can see how this happens.

Creatine Use In Adolescents

Even though it is one of the most studied supplements by science, the number of studies carried out in children and adolescents is very small. Acordin [52] the main reasons are the fear of authorizing research ethics committees, parents, doctors, and nutritionists. Position stand published by the International Society of Sports Nutrition [53], is careful and prudent describes certain criteria surrounding approval from parents, choosing quality supplements, strictly follow following the dosages, and mainly concerned with optimizing diet before supplementation.

On the other hand, [17] examine swimmers (~15y.o.) who were randomly assigned to one of two groups to ingest either 21 g/day of creatine or placebo over 9 days. They found significant improvements in repeat sprint swimming performance after creatine supplementation. Another study, led by [17] tried to replicate these findings in young (~16 y.o.), elite swimmers using 28 days of supplementation (20g/day for 5 days; followed by 5g/ day for 22 days). Despite they found improvement in swim bench test performance, the results failed to replicate improvement in single sprint performance as [17,18] examined the effects of creatine supplementation (5 days; 4 times per day × 5g/day) on mechanical power output and swim performance in highly trained junior (~16 y. o.) competitive swimmers. Significant improvements in sprint swimming performance and dynamic strength following creatine supplementation were observed.

In soccer’s adolescent athletes we found 3 studies that showed positive results in some outcomes after creatine supplementation. [54] verified significant improvements in specific soccer abilities. Were tested 20 young (~17 y.o) male soccer players (7 days of supplementation; 30g/day). In another study, seven days (20g/ day) of creatine supplementation were provided to 17 younger soccer players (~17 y.o.) and significant improvements in repeat sprint performance and dribbling abilities were observed [55]. [19] with elite youth (~17 y,o.) soccer players found significant improvements in power output following a 0.03g/kg/day for 7 days. All these studies were able to demonstrate improvements in many, but not all tests performed, unfortunately, the number of study participants is small and the effect size was not always calculated. Although not an extensive list, a precedent has been set regarding creatine supplementation interventions in adolescent athletes, warranting further research in this area examining both efficacy and safety.

Is Creatine Safe for Youth?

Historically, the concern of creatine supplementation started in 1998 when a young male with focal segmental glomerulosclerosis and relapsing nephrotic syndrome who had kidney disease began creatine supplementation which increased creatinine and was incorrectly presumed to indicate deteriorating kidney function. Two independent experts wrote letters to the journal indicating the error, but speculation surrounding creatine and kidney function has continued [51].

To date, we have not verified studies whose outcomes were directly related to the health of adolescents supplemented with creatine. The studies previously cited in this review provide vague information about some participants who suffered cramps, stomach or intestinal discomfort, and dehydration. None of these findings were investigated to confirm whether the effect was from supplementation or another confounding variable.

Another factor is that these symptoms/signs appeared in young people who used higher dosages (higher and 3.0g/kg per day), but we cannot reliably attribute that there is an association. Based on studies with young people (between 18 and 25 years of age), we can speculate that there is safety in creatine supplementation, but specific studies for these outcomes need to be carried out, whether or not they are safe.

In addition, creatine supplementation has been used for decades as a treatment for diseases with a deficiency of the enzymes that catalyze creatine synthesis. In addition to being successful as a treatment, these children (sometimes as young as 2 years old) do not have any undesirable effects associated with the use of creatine [56-64].

CONCLUSION

The main conclusion of this study is that there is a great deal of misinformation about creatine use by teenagers. If, on the one hand, the number of studies is small to incisively determine that the use of creatine is safe for health, the results of these studies are very promising. It is understandable, but there may be an exaggeration among physicians, nutritionists, and parents regarding the restriction of this supplement. Furthermore, the results related to the improvement of sports performance seem to be much more evident. As a supplement, not a drug, it can benefit young athletes with no side effects and no addiction. Specific studies investigating metabolic and health markers, studies comparing results in boys and girls, and assessments of improvements in cognition are recommendations that the authors give for future studies on the topic.

CONFLICTS OF INTEREST

The authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript.

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