Overall, 13.4% of professional Ugandan athletes in our study used nutritional supplements. Most of these athletes played either basketball or rugby. Athletes who used supplements mostly consumed carbohydrate supplements, energy drinks, vitamin and mineral supplements, protein supplements, and fish oils. These supplements were consumed 3 times per week on average, and most supplements were acquired from a dietician, a local retail store, a pharmacy, or from fellow teammates. Most athletes consumed supplements to improve performance, boost immunity, prevent deficiencies, improve physical appearance, and decrease stress. Regarding perceptions of nutritional supplement use, athletes who used supplements believed that the supplements made them healthier, were safe to use, helped them cope with pain, improved their concentration, and contained doping agents. Most athletes who lacked knowledge about supplements had never used them before.
The prevalence of supplement use among professional athletes in the current study is low compared to what was previously reported ([5, 8, 13, 18]; [6, 14]). One explanation for this finding could be that the assessment tools for supplement use adopted by the current study may have underestimated the true prevalence of supplement use in an athlete population. The reported prevalence of supplement use in the current study compared to the prevalence from a similar study involving rugby players under the age of 16 in South Africa  is low even when corrected for geographic location and population characteristics. Because of the paucity of data on supplement use in developing countries, many parts of the current study tool were adapted from similar studies performed in developed and middle-income countries. As such, less emphasis was placed on the herbal varieties of nutritional supplements, which are indigenous and popular among the local people in Uganda. This may have resulted in under-reporting of supplement use by the athletes. However, it is still possible that the reported prevalence is a true representation, since no dietary evaluation was undertaken to ascertain that the athletes were nutritionally deficient, and thus required nutrient supplementation.
Socio-economic status is a known determinant of supplement use amongst athletes, with athletes of higher education status, or those having higher level paying jobs reported to use supplements more than their counterparts of lower education status, or those with lower paying jobs [3, 4, 25, 26]. These findings partly conform with findings from our study, where nutritional supplement use was significantly higher in athletes with a tertiary education. However, despite its predictive potential from earlier studies [3, 4, 25, 26], athlete’s occupation in the current study had no significant association with nutritional supplement use. Small numbers of supplement users in the occupational sub-groups in the current study possibly confounded this association.
The prevalence of supplement use by athletes of both genders in the current study was similar. This finding corroborates previous observations [3, 4], although it is not consistently reported in the literature [6, 13]. Unlike in previous research findings , the athletes’ age had no correlation with supplement use in the present study. However, the duration of time spent playing the sport was significantly correlated with nutritional supplement use; supplement use was more prevalent among athletes who had competed in the sport for 5-10 years than in their counterparts who had competed for shorter (<5 yrs) or longer durations (>10 yrs). It is proposed that younger athletes (who may share similar characteristics with athletes who have competed for <5 yrs so far) have a lower perceived need for supplementation, because they believe that their diets provide an adequate amount of nutrients .
Additionally, patterns of dietary supplement use are known to differ between different sports. A cross-sectional study involving 2783 Greek athletes found dietary supplement intake to be higher in athletes who were performing in individual sports than in athletes who were taking part in team sports. This is in contrast to the findings from the current study, in which more athletes from team sports, such as basketball and rugby, consumed supplements than their counterparts from individual sports, such as cycling, boxing and athletics. Fixture scheduling could be one plausible explanation for the discrepancies in supplement consumption, since athletes from basketball and rugby usually have more calendar fixtures and competitions than cyclists, boxers and track-and-field athletes. This could imply that team players have less time in between competitions to recover, which could motivate athletes to consider other alternatives that could enhance recovery, such as nutritional supplements. Also of interest in the current study is the fact that none of the participants who played the sport of football used supplements. Similar findings were reported when Sri Lankan professional football players were surveyed for supplement use . A lower socio-economic and educational status for most professional footballers compared to athletes from other sports sub-groups could possibly account for this outcome.
The main athlete motivations for the use of supplements in the current study included improving performance, boosting the immune system, preventing deficiencies, and supplementing diet and are similar to the motivations reported in earlier studies [5, 6, 12, 18]. In addition to using supplements for ergogenic and cosmetic reasons, the most frequent motivations reported by athletes in the current study can be categorized as “health related”. This could imply that some athletes probably used nutritional supplements because they thought their diets could not supply adequate nutrients for their body’s needs. Furthermore, Wardenaar et al.  evaluated elite and sub- elite athletes in Netherlands to understand the adequacy of their intake of micronutrients. From the results of their study, both users and non- users of sports products reported inadequate in-take of the necessary micronutrients. Diets that are scarce in such nutrients are obviously deleterious to athletes, especially those with a rigorous training and competition schedule. More so, many athletes in impoverished parts Sub- Saharan Africa, like Uganda might already be nutritionally disadvantaged compared to their Dutch counterparts.
Carbohydrate supplements, vitamin and minerals, protein supplements, and fish oils were the most frequently used supplements by athletes in our study. This was consistent with findings from earlier studies [6, 8, 9, 11, 12]. The athletes’ motivation for supplement use is known to influence the choice of supplement that is used [13, 18]. In the present study, the fact that the athletes preferred carbohydrates, vitamins, minerals, fish oils and amino acid supplements could be a direct reflection of their motivations for supplement use: improved performance and health. These data are corroborated by findings from another study on athlete dietary habits, where elite Finnish athletes used vitamin and mineral supplements to prevent nutritional deficiencies . Elsewhere, professional Greek athletes cited endurance improvement as the main reason for using amino acid supplements . Due to the popularity of alternative medicine in Uganda, we expected the prevalence of herbal supplement use by athletes in the current study to be high. An earlier study involving Singaporean University athletes identified herbal preparations as a popular supplement used by athletes .The popularity of alternative medicine practice is comparable in both Uganda and Singapore. Surprisingly, herbal supplement use in the current study was low, similar to a report from a Sri Lankan study in which athlete supplement use was low, despite herbal formulations being a popular treatment remedy . In Sri Lanka, just like in Uganda, herbal remedies are used as treatment for illnesses rather than as dietary supplements, a fact that could possibly account for the low levels of intake by athletes in the current study. Nonetheless, considering the risks of contamination with prohibited substances, this could be a key positive finding due to the fact that marketing of herbal supplements is unregulated in Uganda. Moreover, athletes in the current study frequently acquired information regarding supplements from health professionals (nutritionists/dieticians and physicians), media (online sources and magazines), and fellow teammates. With the exception of coaches and trainers (who were the least utilized source for supplement information in the current study), similar sources of information regarding supplements have been reported in earlier studies [6, 8, 9, 11]. Over the past 15 years, internet usage in Uganda has increased by 300-fold, growing from 40,000 users in the year 2000 to over 12 million users in the year 2016 . Most of these users are concentrated in urban areas, which is representative of most of our study respondents. This could explain why online media sources were the most common sources of information in our study, since the internet is a readily accessible outlet containing information about supplements. Additionally, we postulate that some athletes might avoid coaches/trainers due to a recent anti-doping push targeting elite athletes and those seeking to compete at the world stage. Sottas et al (2011) reported that the International Association of Athletic Federations (IAAF) introduced blood testing in 2001 and advocated for strict adherence of the protocol, effective from 2005. We also speculate that athletes in our study believed that their coaches/trainers lacked the required expertise to offer advice on nutritional supplements, and thus, athletes were hesitant to seek information from them. This speculation contrasts with earlier findings where athletes preferentially relied on information sources for which accuracy was not guaranteed [6, 11]. Nonetheless, licensing requirements for coaches/trainers in developing and developed nations are different. The minimum requirements for obtaining a coaching/trainer license in most developing countries are not as stringent as those in middle- and high-income countries. In high-income countries, even though most coaches possess a bachelor’s degree or higher, coaches are additionally required to complete specialized coaching education before they can be certified. The curriculum for this specialized coaching education contains a module about sports nutrition. Some coaches from developed countries even undertake additional nutrition training as part of their continued professional development because they can afford it [29–31]. These extra modules ensure that these coaches are better prepared to address nutritional concerns for their athletes than are their counterparts from developing countries.
Athletes in the current study often obtained their supplements from personal or team nutritionists/dieticians, retail stores, pharmacies, or from teammates, which represents an obvious reflection of the athletes’ preferred sources of information regarding nutritional supplements. Depending on whether an athlete used supplements, the response to different statements regarding supplement use was different (Fig. 7). Generally, athletes who used supplements in the present study thought that supplements made them healthier, were safe to use, helped them cope with pain, improved their concentration, and contained doping agents. Even though the current study used these statements to elicit athlete perceptions of supplement use, these statements have previously been used to provide insight into the perceived awareness of athletes on supplements . Knowledge about supplements is believed to deter athletes from using supplements, and a greater understanding of supplements is associated with diminished use of supplements . In contrast, the majority of athletes in the current study who responded with “I don’t know” to different statements regarding supplement use either were not using at the time or had never used nutritional supplements. However, our findings agree with previous findings  showing that British track junior national track and field athletes who used nutritional supplements had greater knowledge levels about supplements.
The major limitation of the current study is that we may have underestimated the true prevalence of supplement use among athletes. Taking into consideration the popularity of alternative medicine practice in Uganda, the assessment tool that we adapted to collect data on herbal supplements did not capture the broad range of herbal supplement formulations and varieties that are unique and indigenous to Uganda. However, the remaining items on the adapted questionnaire had been standardized in earlier studies [22, 23]; [6, 24]. This facilitated comparisons between our data and data that were generated from earlier studies. Furthermore, due to the small number of supplement users in our study, we were unable to complete more robust statistical analyses to examine further associations between factors among nutritional supplement users. However, the 100% response rate of athletes and the adequate statistical power in our study ensured that a satisfactory comparison was made between athletes who used supplements and those who did not.
Most athletes use supplements because they believe their diets do not adequately meet their daily nutritional needs. We did not assess for the nutrient content of the athletes’ diets, so we cannot speculate on the relationship between athlete supplement use and dietary nutrient adequacy. Designs for future studies should take these factors into consideration.