Nutritional Intake and Dietary Knowledge of Athletes: A Scoping Review

The search was limited to open access articles, published in English since 2010. As research in the sphere of nutrition, sports science, and dietary education is a rapidly evolving field, all of the included articles have been published since 2010. This restriction allows for only the inclusion of evidence that reflects current practices, knowledge and information that is up to date and relevant. Table 1 depicts studies based on year of publication. The search parameters were then further refined to exclude any studies that included minors, non-athletes and non-peer-reviewed articles. Studies included participants over the age of 18. A diverse level of competitiveness was included; this ranged from recreational to elite athletes, and a range of sporting disciplines were included. These strict criteria ensured the inclusion of high-quality, applicable literature with a specific focus on the study population and concept.

The exclusion criteria for this study applied to studies that involved minors (under 18 years of age), or non-athlete populations, or whether the studies were not peer-reviewed. This ensured there was relevance and rigor to the studies included. The specifics of the inclusion and exclusion criteria allowed the author to narrow down the search to include studies that specifically addressed the inter-relationship between performance and dietary knowledge of adult athletes within a peer-reviewed context.

A systematic search strategy was developed and conducted to identify relevant sources related to the conceptual model and the developed PCC (Population, Concept, Context) framework. This framework defined the population for inclusion as athletes and included a diverse range of age groups whilst excluding minors. A diverse level of competitiveness was included encompassing athletes ranging from recreational to elite. A range of sporting disciplines were included. The underpinning concept focused on nutritional knowledge. This can be defined as an understanding of dietary guidelines, nutrient needs, and practical application, in turn influencing one’s health [10]. The context of this review encompassed a range of environments, for example, where athletes engage in training, competition and recovery. This, in turn, will highlight factors that influence nutritional behaviors. Key words were extracted and selected from the initial research question, aim and objectives of this study. The search strategy had a specific focus on papers related to athletes’ nutritional knowledge, dietary intake and players’ performance and recovery with reference to sports nutrition. The aim of this strategy was to comprehensively capture indicators of the relationship between sports nutrition science, performance, nutrition knowledge and dietary intake within the context of sport.

The keywords and search terms were carefully selected to ensure the retrieval of relevant literature. The initial search terms included “sports nutrition” and “athletes’ nutritional knowledge” and “Dietary Intake”. These terms are directly aligned to and target the specific athlete population under study. These terms were then combined with specific inter-related keywords including “Performance”, and terms that are directly related to dietary knowledge and food literacy in sports, including “food literacy in sport”, “nutrition education”, “nutrition”, and “diet”. In addition to these terms, further key words including “food” and “food intake” were utilized to capture further studies with a focus on dietary behaviors of the study population. See Table 1 for the inter-relationship of search terms derived from each concept.

To further refine the search, Boolean operators (AND, OR) were used to combine keywords. The terms “Sports nutrition” and “athletes’ nutritional knowledge” were subsequently paired with the terms “Performance” AND “nutrition education” AND “food literacy in sport”, AND “nutrition” OR “diet”, thus ensuring that the search results incorporated a broad range of relevant studies.

Following the framework of Arskey and O Malley [8], databases including Pub-med, Sports Discus, Sage, EBESCO along with gray literature were screened for papers matching the initial search terms and criteria. These databases were included due to their relevance to sports science, nutrition, and health research. Other databases were excluded due to limited coverage of the key concepts. There was also consideration of gray literature. This included reports and informal studies. This aided in capturing a full picture of the pertinent research within this area and allowed for a more comprehensive mapping of the topic. The initial search retrieved a total of 1375 articles from the peer-reviewed literature. A comprehensive literature retrieval such as this was essential to ensure that no relevant studies were overlooked in the initial screening stages. Following the removal of duplicate records (n = 106), the remaining articles (n = 1269) underwent a further screening process. This screening was conducted at both title and abstract levels to assess the relevance of each study to the research focus. Articles passed initial screening if their title contained words or sentences that were included in the search terms derived from the underpinning concepts (Table 1). After this detailed screening process, eligible studies were then uploaded to referencing management software Zotero 6.0.26. The remaining articles (n = 51) were then exported to Rayyan screening software, https://new.rayyan.ai/↗ (accessed on 9 November 2024). Rayyan is a software used for research collaboration. Rayyan was used to promote rigor in the search strategy, and to facilitate and streamline the selection of eligible papers. Two reviewers (E.M., C.H.) were consistently involved and independently blind-screened all article titles and abstracts against the inclusion and exclusion criteria. Conflicts between reviewers were resolved by a third reviewer (A.M.C.). The reference lists of eligible articles were then searched for identification of the relevant literature for inclusion. Each of the included studies met all the criteria and were found to be directly relevant to the nutritional knowledge and dietary intake of athletes within the context of the PCC framework. Following Rayyan screening and selection, 21 papers were deemed suitable for inclusion in this scoping review. A basic appraisal of the quality of each included study was conducted to identify any potential biases and, in turn, assess the reliability of the findings presented.

The final selection of 21 studies provided a robust foundation for the scoping review, offering insights into the relationship between nutritional knowledge and dietary intake of athletes. The process of screening to include the selected studies is depicted in Figure 1. For each included study, the author, year of publication, country, study aims, population, sample size, methods, key findings and conclusion were mapped to depict relevance of the findings (Table 2).

Fourteen of the twenty-one included studies within this scoping review highlighted a generally low to moderate level of nutritional knowledge among athletes. Mc Crink et al. [6] conducted a study on the nutritional awareness of Irish Gaelic football players. The findings of this study indicated that despite their status as competitive athletes, many of the study cohort had poor to average nutritional knowledge and lacked a comprehensive understanding of nutrient requirements, timing of nutrient intake, and the role of hydration in athletic performance with 19% of these athletes being dehydrated prior to exercise and exhibiting prevalent nutrient deficits [6]. The substandard nutritional knowledge was also echoed in a study by Mitchell et al. [13] with no significant differences in dietary knowledge observed between elite and amateur players. These findings were further reinforced in a study by O’Cathain et al. [14] with Gaelic football players failing to meet sports nutrition guidelines. Within an international context, similar practices are mirrored; a study by Trackman et al. [5] investigated Australian football athletes’ (elite and amateur) lack of awareness of current sport nutrition guidelines. The findings indicated that knowledge of macronutrients, weight management and alcohol was more advanced than knowledge of supplementation, micronutrients and key sports nutrition guidelines [5]. These findings within the Australian context remain consistent with the Irish cohort. It was further suggested that the gap in knowledge and awareness often led to suboptimal dietary intake that could hinder performance. However, there was some evidence that on “game day”, purposeful nutritional planning was evident [14]. Murphy and O Reilly [12] investigated the association between nutritional knowledge and dietary intake amongst a sample of Irish male hurling players, also falling under the umbrella of Gaelic football games. Nutritional knowledge was measured using a validated Sports Nutritional Knowledge Questionnaire (SNKQ). A total of 266 participants ranging from amateur to elite were selected for inclusion. Again, nutritional and energy intake deficits were reported, with the intentional limit of carbohydrates to reduce body fat negatively impacting performance. Avenues used by athletes to acquire information were also noted as a cause for concern [4]. Malsagova et al. [27] described how dietary accessibility, social support, habits, and, in particular, marketing can influence dietary behaviors. There is also a growing phenomenon of social media influencers promoting products to enhance performance. However, the overall impact of these factors is unclear, and further research in this area is required.

Malsagova et al. [27] further discuss how nutrition is considered to be the cornerstone of athletic performance and highlight the importance of adequate consideration of post-workout nutritional recommendations as being fundamental to the effectiveness of the recovery and adaptive processes. This statement contrasts with the awareness of nutritional guidelines and dietary intake of the athlete population in relation to nutrient recommendations. One study in particular, by Boucherville et al. [26], evaluated the nutritional knowledge of recreational athletes. Findings of this study indicated that significant gaps exist in participants’ knowledge of sports nutrition. This is also reflected in a study by Trackman et al. [5] where athletes demonstrated proficiency in knowledge of macronutrients, weight management and alcohol, superior to knowledge of supplementation. Non-elite respondents demonstrated greater proficiency and higher scores than elite players. These findings remain consistent across the literature. The gaps are particularly prevalent in relation to knowledge of nutritional recommendations for the macronutrients protein and carbohydrate. A majority of the participants in this study demonstrated proficiency in knowledge of post-workout protein requirements; however, less than half of the participants (40.8%) could correctly identify the recommended daily protein intake for athletes [26]. These findings further indicate that knowledge of the impact of carbohydrate requirements during exercise was better understood than protein, with 63.8% of participants knowledgeable of the impact of carbohydrates in relation to energy requirements and its role in stabilizing blood sugar levels; however, in contrast, a minority of participants (37.9%) demonstrated awareness of the recommended nutritional intake of carbohydrates during exercise. This study also highlighted a gap in hydration knowledge and practices. A minority of participants (10.5%) demonstrated proficient knowledge of the role of hydration in maintaining adequate blood volume during training. In general, these findings further highlight the need for further education in sports nutrition specifically tailored to address this gap. This is also seen on an international scale as demonstrated in a study by Jessri [17]. This particular study was conducted with Iranian basketball and football players. The findings of this study indicated that female participants demonstrated greater proficiency than males, and there was a clear need for evidence-based nutritional guidance. Parks et al. [21] describe that as athletes face nutritional barriers, there is an inconsistency with the source of information and that perhaps a collaborative approach between the trainer/coach and dietician may be a mode to enhance the delivery of evidence-based nutritional knowledge. It was also noted in a study by [23] that there is a need for more targeted nutritional educational plans encompassing a multi-disciplinary approach.

Education surrounding the significance of carbohydrate intake and its importance in supporting training and performance is warranted amongst athletes [28]. Findings further indicated that protein intake was generally met or, in some cases, exceeded recommended intake, which supports Trackman’s [5] findings. In general, the recorded suboptimal dietary practices of athletes strengthens the argument for improved, tailored nutritional knowledge and awareness to promote optimum performance and health.

A key concept within this review, and recurrent in the findings, is that of good nutritional intake and what it constitutes. Good nutritional intake of athletes encompasses a diet that meets an athlete’s specific energy, macronutrient, and micronutrient requirements to support optimal performance, recovery, and overall health [29]. While the needs of athletes can vary based on a variety of factors including sporting field, training intensity and individual physiology, mainstream dietary guidelines can offer a general framework for balanced nutrition. Interpretations of a what a good diet is may differ widely due to cultural influences, individual dietary philosophies, and exposure to emerging dietary trends.

This scoping review found that there was a varied approach to the dietary practices of athletes. Several common threads were highlighted including insufficient carbohydrate intake and inadequate pre- and post-training nutrition. Mc Daid et al. [30] reported the role of the commercial food industry and the reliance on supplementation. Findings of this study indicated that the routine use of food supplements was reported by approximately 60% of the study cohort. According to the European Parliament [31], a food supplement is used to complement the diet causing a concentrated nutritional or physiological effect. It can be found in various forms including tablet, pastilles, powder sachet or liquid [31]. It is designed to be consumed in small unit quantities.

The use of supplementary nutrition suggests that players might be compensating for dietary gaps with products rather than whole foods [30]. A study by Sánchez-Oliver et al. [24] explores the effects of supplementation on the athletic performance of rugby players. The study focused on the role of supplementation in enhancing energy availability, recovery and, in turn, overall health. It highlighted the efficacy of specific supplements (protein and creatine) in supporting muscle repair and improving strength and endurance. The most common motivation for this supplementation was enhanced performance. The findings emphasize the importance of sound evidence-based supplementation practices to maximize benefits and minimize potential risks for athletes as some of these products are purchased online. Mc Daid et al. [30] state that the most frequently reported types of food supplements consumed are those of protein, Vitamin D and Vitamin C with each popular amongst both elite and amateur athletes. Further to this, a study by Duggan, Collins and Keane [32] investigated the dietary intake of female Irish Gaelic games athletes. This study reported suboptimal intakes of key micronutrients amongst this cohort. This reiterates the need for further research in this area and a targeted approach to address this gap in knowledge and practice. Jenner et al. [33] indicates that a targeted nutritional intervention strategy could be a practical method of improving dietary intake, in turn benefiting a broad range of athletes within differing sporting disciplines, who are currently failing to meet nutritional recommendations.

There is well-established evidence that there is a direct correlation between dietary intake, performance and recovery in field-based team sports including soccer and rugby. O Caitlin et al. [14] conducted a study to determine the dietary intake of Irish Gaelic games athletes, and findings indicated that regardless of playing level, players consumed less than the recommended level of carbohydrates to support optimal performance and recovery; however, results showed that protein and fat were consumed in line with general sport nutrition guidelines. Mc Crink et al. [6] examined the relationship between dietary intake and performance outcomes. In contrast to the reported macronutrient deficits, diets high in carbohydrate were consistently associated with improved energy, performance, endurance and reduced levels of fatigue during matches. This was also noted by Mc Guire [28], where exercise energy expenditure was greater that energy availability. Surprisingly, in this study, Gaelic football players failed to meet the recommended energy intake levels, and therefore, there is an increased risk of low energy availability and decreased performance. This particular study examined energy availability in 20 elite male Gaelic football players. These findings are consistent with a study conducted by Werner et al. [16] who assessed the nutritional knowledge of college athletes. Findings of this study indicated that athletes had lower nutritional knowledge. This, in turn, increased the athletes’ risk factor for decreased athletic performance and increased risk of injury.

Adequate protein intake was reported, and this could be directly linked to faster recovery times and better muscle maintenance. Supplementation of protein was also widely reported. Evidence exists to support the consequences of poor hydration strategies [34] as cited in Duggan et al. [32]. The results of that study found that 25% of female athletes were recorded as dehydrated pre- and post-exercise, much lower than their male counterparts that reported 35% and 48%, respectively. Further to this, the ill effects of dehydration on performance can include an increase in core body temperature, cardiovascular strain, and impaired cognitive performance. Proper hydration has been shown to positively impact cognitive function, decision-making, and overall performance.

Limited understanding and application of sports nutrition can contribute to a macronutrient deficit. This, in turn, can lead to increased fatigue, a greater risk of injury, and prolonged recovery. Furthermore, inadequate dietary practices can also result in long-term health consequences, some of which include chronic energy deficits and metabolic disruptions. This further highlights the need for sound nutritional knowledge and dietary practices to promote performance and recovery and, in turn, strengthens the argument for the need of targeted nutritional interventions.

The need for targeted nutrition education programs, specifically tailored to meet the needs of athletes due to poor dietary behaviors and lack of nutritional knowledge, has been acknowledged [35]. A study by Lydon et al. [15] aimed to assess the impact of a food skills and nutrition education workshop, with young Gaelic football players, on cooking skill efficacy, food literacy and willingness to adopt positive dietary practices. The study highlighted that many athletes struggle with the practical application of knowledge due to insufficient skills. It also showcased a gender disparity with females exhibiting greater confidence with practical application. The effectiveness of a tailored nutritional intervention was proven to effectively improve nutritional knowledge, cooking skills and application of nutritional guidelines. Studies that implemented educational models reported more positive outcomes, including increased carbohydrate intake, improved hydration strategies, and better overall dietary quality [25]. Renard et al. [11] conducted a study to assess the inter-relationship between cooking and food skills confidence among 266 team sport athletes. Results indicated that females had higher confidence levels in both cooking and food skills. This is also echoed by Murphy and O’Reilly [12]. The results showed that factors including gender, culinary training, health interest and food engagement had a significant bearing on confidence levels. These results suggest that male athletes may benefit from targeted educational interventions to improve these skills [11,19]. These findings suggest that targeted nutrition education can effectively motivate behavior change and support athletic performance. This further highlights the need for further exploration of the motivational factors for enhanced dietary practices. Participation in meal preparation has been associated with improved eating behaviors, and the benefits have been showcased with the lasting impact carrying into adulthood [36]. Further to this, only 14.2% of one study cohort reported having previously accessed nutrition education, and this was primarily at the elite level [13].

This scoping review identified a number of barriers and challenges faced by athletes in accessing and maintaining optimal nutrition. These challenges included a lack of access to professional nutritional advice, lack of baseline nutrition knowledge assessment, lack of evidence-based knowledge on supplementation and time constraints due to balancing sports, work, and other commitments [5,25,37]. Additionally, cultural factors and personal dietary preferences were found to influence dietary choices, sometimes leading to suboptimal nutritional practices [22,38]. A study by Brauman [20] explored the barriers faced by college-level athletes when it comes to maintaining a healthy diet. The main significant challenges isolated were lack of time, easy access to unhealthy foods, cost of healthy foods, and lack of nutritional knowledge and cooking skills. “Lack of time” was commonly cited and therefore was the top barrier. This theme reflected the athletes’ busy schedules with classes, training, and social commitments. This aligns with findings from Beasley [37]. Additionally, the cost of healthy food was particularly relevant for male athletes living in off-campus accommodation and was also cited as a barrier. This further emphasizes the financial burden associated with healthier eating habits. There is, however, minimal research in the area of the practical challenges athletes can face in achieving optimal nutritional intake. Research is lacking within the sphere of socioeconomic factors influencing dietary choices, cultural influences and accessibility to quality food or supplementation. The study highlights the importance of targeted nutritional education programs to address these barriers. A targeted nutritional educational model could address areas including time-management strategies, nutrition education, hydration practices and basic food preparation skills [18,22,25]. These skills could support student athletes in achieving optimal dietary behaviors. An improvement in nutritional knowledge is likely to have a profound impact on dietary behaviors, training adaptation and thus match performance [25]. Another significant challenge highlighted was the varying levels of nutritional knowledge among players and coaches, with some studies indicating a need for better education and awareness regarding the importance of nutrition in sports performance.

Given the level of nutritional knowledge among athletes, many studies have highlighted the need for tailored nutritional intervention programs to provide players with evidence-based nutritional advice and practical food skills [6,14]. Mitchell et al. [13] carried out a study to determine nutrition knowledge in elite and non-elite players, and findings indicated that there was little to no difference between the respondent’s nutritional knowledge based on playing level. They further reinforced the importance of nutritional education at all levels of competition. Females were however under-represented in this sample; conversely, a study by Werner et al. [16] showed participants (>50% female), in general, having poor nutritional knowledge with females scoring higher on nutritional knowledge, significantly better than male counterparts. In turn, the contemporary literature in this domain has indicated a deficit in nutritional knowledge, and there persists a need for an innovative nutritional educational model that targets this cohort [4].