Prevalence of the use of sports supplements
The survey showed that 82.2% of athletes were using sports supplements among which 60.6% were male athletes. The analysis revealed that 47.7% of athletes were 15–16 year olds (p = 0.038) and 52.3% were 17–18 year olds (p = 0.032). Furthermore, male athletes were more prone to the use of sports supplements in both age categories (56.8 and 64.0% in 15-16Y, (p = 0.029) and 17-18Y, (p = 0.021), respectively).
The study revealed that 82.2% of athletes used 1–2 different supplements at the same time, 62.1% 2–3, and 35.9% 3–4, while 14.7% of athletes used 4 and more. Biplot in Fig. 1 shows the projection of the correspondence analysis (total inertia of 0.6955, χ2 of 64.682, p = 0.007) of number of supplements taken by different sports, among which kayak, swimming and karate were identified as the one with the highest number.
Figure 2 shows that whey protein usage by 54.5% of athletes can be observed, together with the prevalence of ten other sports supplements. The males use more (p = 0.030) whey protein, creatine, amino acids, caffeine and NO reactor compared to females who take more vitamins and mineral complexes, while there is an almost equal use of energy drinks, glutamine and carbohydrates between sexes. Between the age categories the use of protein supplements and consumption of energy drinks were equally distributed; younger athletes tend to use more carbohydrates, beta alanine, glutamine, vitamins and mineral complexes versus 17-18Y athletes who take more creatine, caffeine, NO reactor and amino acids.
Reasons for the use, attitudes, supplement source and source of information regarding sports supplements
When asked how important good nutrition and proper supplementation is for enhancement of athletic performance 30.2% of athletes thought that it is very important, while 18.4% though it is unimportant (Fig. 3a).
The main reasons the athletes gave for taking supplements are presented in Fig. 3b with the improvement of their athletic performance (35.3%) being the predominant one. Female athletes were significantly (p = 0.047) more likely to take supplements “for their health” while males use it for boosting of athletic performance.
The attitudes of the athletes who do not take supplements were expressed through the following statements: I don’t need them (48.4%); I don’t know enough about them (21.0%); they are unhealthy (14.5%); they are expensive (8.1%); using supplements is like cheating (4.8%); they are not allowed (1.6%), I fear of a positive doping test (1.6%).
Considering the “unclear picture” regarding the health safety and quality of sports supplements and their impact on athlete’s health, 72.1% of athletes were aware of a certain health risk, 14.9% thought they are risky and 12.9% of athletes consider them safe.
Supplement safety information were gathered from the coach (38.2%), dietician or medical professional (33.3%) or the declaration on the product (20.1%). The athletes rely less on their own research about the health impact of the sports supplements (8.3%).
The majority of athletes, mostly males and 15-16Y reported that they obtained information regarding sports supplements from their coach (41.4%); likewise 17-18Y athletes rely on the Internet as shown in Fig. 3c.
Athletes mostly procure sports supplements in specialized retail stores (59.1%) as shown in Fig. 3d. There was no significant statistical difference (p > 0.05) between age categories concerning the answers to the question where they buy sports supplements. However, male athletes tended to use more online shopping in acquiring sports supplements than females.
Knowledge about proper and intended use of the sports supplements
One of the main goals of this international study was to assess the young athletes’ understanding of the proper and intended use of the sports supplements. The level of knowledge was assessed by conducting an enquiry about the proper timing (before, during or after training), right serving amounts and the main reason for their use. Graphical presentation of correspondence analysis is presented in Fig. 4. A significant correspondence (p = 0.008) was found between the considered categories, representing the total inertia of 0.141 and χ2 value of 214.88. The first two dimensions account for 74.5% of the total inertia. Substantial differentiation between the proper use and sources of information among different demographics can be observed.
Unfortunately, young athletes lacked proper knowledge about the use of creatine (11.1% of athletes responded correctly), beta alanine (20.0%), amino acids (20.0%), NO reactor (22.2%), glutamine (37.5%), protein (38.5%), and carbohydrates (48.3%). Yet they seem to have more knowledge about sports drinks (50%), caffeine (61.8%) and vitamins and mineral complexes (71.0%). Previous attendance at educational seminars influenced the right answers about the use of creatine (75% of athletes previously attended seminars), amino acids (66.7%), carbohydrates (57.1%), proteins (55.0%), vitamins and minerals (52.6%), caffeine (50.0), NO reactor (50%), glutamine (46.7%), sports drinks (44.4%) and beta alanine (33.3%).
Athletes 17-18Y showed better knowledge than 15-16Y (r = 0.968; p < 0.001), as well as female athletes compared to males (r = 0.953; p < 0.001). Athletes from all 4 countries were among the ones who knew the proper use of supplements: Serbia (r = 0.9013, p = 0.003), Germany (r = 0.9302, p < 0.001), Japan (r = 0.954; p < 0.001) and Croatia (r = 0.979; p < 0.001). Younger athletes (15-16Y) had better understanding of the proper use of creatine (87.5%), carbohydrates (67.9%), sports drinks (66.7%), beta alanine (66.7%), and caffeine (55.9%), while the older athletes (17-18Y) gave the right answers when it comes to the proper use of glutamine (60.0%), vitamins and minerals (60.5%), proteins (70.0%) and amino acids (86.7%). Male athletes were better informed on the right use of NO reactor (100.0%), creatine (75.0%), amino acids (66.7%), protein (60.0%) and glutamine (53.3%), while the female participants were more educated in the proper use of caffeine supplements (73.5%), carbohydrates (71.4%), beta alanine (66.7%), vitamins and minerals (56.6%) and sports drinks (55.6%).
The coach was the only source of information regarding the proper use of creatine. The coach was also the sole source of information for 83.1% of athletes about proper carbohydrates use, amino acids (73.3%), caffeine (73.3%), sports drinks (72.2%), glutamine (53.3%), NO reactor (50.0%), protein (40.0%), beta alanine (33.3%), and vitamins and mineral complexes (32.9%). The 15-16Y athletes took supplements properly according to the coach’s advice (r = 0.912; p = 0.003). The older athletes (17-18Y) gathered information from the Internet (r = 0.942; p < 0.001) and have attended the seminars about that topic (r = 0.963; p < 0.001). Athletes in Serbia had a better understanding of the proper use of proteins (50.0% of right answers), while athletes in Japan were better educated on the use of vitamins and minerals (32.9%). Furthermore, athletes from Germany had a better understanding of carbohydrates (35.7%) and creatine (50.0%). Croatian athletes showed good recognition of sports drinks (50.0%).
The physician was the source of information for 36.8% of athletes about vitamins and mineral complexes, while others used the Internet. Athletes who used sports supplements properly attended more seminars about sports supplementation than others (r = 0.967; p < 0.001). Male athletes gathered the information on how to use sports supplements using the Internet (r = 0.951; p < 0.001) and attending seminars (r = 0.961; p < 0.001), while female athletes were mostly advised by their coaches (r = 0.892; p = 0.007). Also, athletes from Serbia used the Internet as a source of information more than athletes from other countries, who knew the proper way of using sports supplements (r = 0.971; p < 0.001).
Only 27.9% of all surveyed athletes had the opportunity to work with dieticians in their sports clubs, but only 20.0% of those who answered correctly about the proper use of sports drinks and proteins and 3.6% about carbohydrates used that opportunity. Mostly, athletes from Germany had a dietician in their clubs (r = 0.778; p = 0.006). Athletes in Germany and Japan who answered correctly about the use of supplements attended more seminars (r = 0.927; p = 0.004 and r = 0.923; p = 0.004, respectively) and utilized more advice from dieticians, rather than athletes from other countries (r = 0.824; p = 0.003 and r = 0.882; p = 0.003, respectively).
Risks of doping and ethical dilemma
Awareness and caution about possible risks of doping is the key for proper supplement use, following regulations of the World Anti-Doping Agency (WADA). This study revealed that only 55.5% of athletes had the access and are familiar with these regulations. When asked if they would be willing to use prohibited substance to enhance their athletic performance if they knew that they would not be tested by WADA, 11.8% of athletes gave a positive answer.