Nutrition Knowledge of Collegiate Athletes in the United States and the Impact of Sports Dietitians on Related Outcomes: A Narrative Review

A wide variety of nutrition-related issues commonly affect student athletes across the spectrum of body composition and type of sport. Low energy availability (EA), defined as an inadequate amount of dietary energy remaining for physiological function after exercise, is commonly seen in all categories of student athletes [3]. Low EA may arise from either an intentional or unintentional caloric deficit and is often accompanied by an athlete’s lack of knowledge about their nutrition needs. Athletes with relative energy deficiency in sport (RED-S) are in prolonged states of low EA and are at increased risk for infection, illness, fatigue, and nutrient deficiencies, as well as musculoskeletal, endocrine, gastrointestinal, renal, psychological, cardiovascular, and performance detriments. Athletes present with altered hormone levels, unfavorable body composition, catabolic markers, and menstrual dysfunction in females when large energy deficits are maintained long-term [3,4]. Poor carbohydrate, iron, and calcium intakes are commonly observed, especially among female athletes [5]. Likewise, as many as 80% of competitively trained male endurance athletes may be at risk for low EA [6], which is accompanied by impaired athletic performance, fatigue, basal metabolic rate, mood, and higher visceral fat deposition as well as increased risk for dehydration, injury, and illness [7]. The total energy needs for female volleyball players can be as high as 2815 kcals (±306) per day, or 39 to 44 kcal/kg of body weight, to support their higher percentage of lean mass [8]. Many female athletes consciously or unconsciously restrict their intake of carbohydrate below the recommended range of 6–10 g/kg of body weight, or what is needed for the maintenance of glycogen stores [9]. It is important for proper nutrition intake to be completed so that the current energy and nutrient consumption can be assessed, and changes can be made. These methods include 24-h recalls, food frequency questionnaires, diet history, and food records. Twenty-four-hour recalls can either be completed as a single day or for multiple days. The accuracy of this method is improved by proper training and using a multi-pass system that makes sure to catch any forgotten foods and drinks. Food frequency questionnaires look at trends in usual intake instead of single days individually. These are better for addressing whole-team diet trends and may under-estimate individual differences in dietary patterns. Diet histories are conducted by trained professionals who ask about typical diet patterns and behaviors that are associated with the diet pattern. These may include clinical symptoms, sleep, supplement, lifestyle, and exercise factors that may influence or be influenced by the individual’s diet. A final way for nutrient assessment is food records. These are written journals of everything the individual eats and drinks throughout the day and can include weights of foods and more details than other methods. Food records often require training of the individual on measuring food quantities and individuals may alter diet patterns since they are more aware of diet choices and the nutrients associated with each food [10].

Eating disorders are common in athletic populations, with recent estimates indicating as many as half of all athletes in aesthetic-focused sports, such as track and field, may present with features of disordered eating [11]. The gender gap in eating disorder risk may be narrower in athletic populations than in normal populations, with as many as 19% of male college athletes presenting with symptomology of a clinically relevant eating disorder [12,13]. A study of 111 male student athletes found previous food insecurity was associated with disordered eating behaviors such as preoccupation with food and hiding food in athletic locker rooms [14]. Disordered eating that results in insufficient dietary intakes may be associated with additional negative physical consequences similar to RED-S and may include symptoms such as urinary incontinence in female athletes [15].

Outside of micronutrient deficiencies associated with inadequate energy intake, several micronutrients have direct correlations with athletic health and performance. Research is limited on ideal micronutrient intakes, but many micronutrients have the potential to impact sports performance if they are deficient. Thiamin, riboflavin, niacin, and pyridoxine all have important roles in energy status and metabolism within the cell. Since athletes have higher metabolic need and increased energy usage, they may see performance decrements even at subclinical levels. B12 and folic acid aid in hemoglobin formation while vitamins A, C, and E are all crucial for reducing oxidative damage. These vitamins all could decrease endurance performance if subclinical deficiencies exist [16]. Adequate iron status and fitness have been observed to yield combined positive effects on performance in classes [17]. The prevalence of iron deficiency is greater in athletes and active people, with occurrence rates in 20–50% in female athletes and 4–50% in male athletes [18,19]. Vitamin D deficiencies are common in student athletes, especially in indoor sports and during winter months when sun exposure is limited. Halliday et al. found that supplementation could play a role in disease prevention for college athletes. Further research may support nutrition’s role in cognition and injury prevention [20].

Sport-specific events and positions, such as American football linemen and track and field throwers, attain mechanical advantages by maximizing their body size. The deliberate accumulation of large amounts of body mass, with body weights often exceeding 300 pounds, may place undue strain on the heart [7,21,22]. Several longitudinal studies have observed concentric left ventricular hypertrophy among football players, with mortality due to hypertensive heart disease and coronary artery disease increased by more than half (52%) among former football linemen [17,18]. Former football players with a BMI greater than 30 during their years in sport had close to double the risk of CVD mortality of other players (hazard ratio: 2.02 [95% CI, 1.06–3.85]) [23]. Other research studies have included metabolic syndrome (MetS) in order to investigate both cardiovascular risk and other factors to see the greater picture of the health of college football players. Linemen were more likely to meet MetS criteria in both high school and college settings than any other position or skill player. Higher body fat levels were also predictive of arterial blood pressure, HDL, and waist circumference [24].

Given the previously outlined nutrition-related problems in collegiate athletes, we sought to answer the following questions through this narrative review of the published literature: “Are current nutrition knowledge and practices among NCAA student athletes sufficient to meet established needs?” and “Do sports RDs positively impact nutrition knowledge and behavior in NCAA student athletes?”.

One hundred twenty-one papers and 253 papers were retrieved from the (dietitian and athlete) and (athlete and nutrition and knowledge) searches, respectively. One hundred sixty-one and 72 were excluded due to geographic location, and the remaining exclusions were due to the wrong study population and/or not an observational or interventional study. The remaining fourteen studies are presented as assessing nutrition knowledge (Table 1, n = 8) or reporting the efficacy of dietitians (Table 2, n = 6).

In a 2016 study by Andrews et al., 123 student athletes from a Division I (DI) university with no sports dietitian on staff completed a questionnaire to determine their sports nutrition knowledge. While a predetermined mean score of 75% represented adequate knowledge, the mean score for this group was 56.9%. Only 12 student athletes out of the group scored 75% or higher, and there were no differences by team, class level, gender, or completion of prior nutrition coursework [25]. A group of 77 male and female college-aged indoor or sitting Paralympic volleyball players were given the sports nutrition knowledge questionnaire (SNKQ) developed by Zinn, Schofield, and Wall (2005). The mean raw score on the SNKQ of this group was 40.22 ± 8.39 out of a possible 88.00, a percentile score of 46 ± 9%. No athlete made the established passing score of greater than 70% on the quiz [26].

Madrigal et al. surveyed 196 student athletes about their nutrition knowledge and regrets over past eating and drinking habits. The strongest regrets were related to diet quality and inadequate fueling. Average scores were 48% for males and 49% for females and less than 25% for questions related to supplements, all of which were below the minimum values representing adequate knowledge. There was no association between nutrition knowledge and nutrition-related regrets, suggesting that even with the knowledge that they do have, student athletes need more help with behavior change [27]. Shriver et al. assessed the dietary intakes and eating habits of NCAA DI female college athletes and found that there were several sports nutrition standards that most were not meeting. The total calorie and carbohydrate intakes were below recommended minimums (p < 0.001), with only 9% meeting their daily energy needs and only 25% consuming the minimum amount of carbohydrate required for training. In addition, the vast majority (73%) did not eat a regular breakfast, and only 16% monitored their hydration status [28].

Brown et al.’s research suggests that football teams have a high degree of interest in working with a sports dietitian. One study assessed the nutritional needs of a DI football team who did not have an RD or training table, as well as their attitudes towards expanding the provision of nutrition services. Sixty-seven football players (90% of the team) completed a questionnaire, and their fueling and hydration strategies were noted to be insufficient for promoting optimal performance. A majority of the team (80–92%) did not comply with well-known nutrition strategies for football teams (92% did not consume a pre-game snack, 88% did not consume a pre-practice snack, 80% only drank water during exercise), and 75% reported a lack of energy during workouts. Interest in food and nutrition assistance was widespread, as 93.4% believed that they would benefit from a training table, 91% would be willing to meet with a dietitian, and 97% believed that proper nutrition would enhance their football performance [29].

In a similar study with DIII football athletes, a mean score of 55.2% on a nutrition knowledge questionnaire showed a poor understanding of nutrition. Less than half of the athletes consumed a daily fruit and vegetable while lineman had the greatest health-adverse dietary choices. Athletes that had been exposed to nutrition education through coursework had significantly higher results than the others [30].

A study of DIII student athletes at multiple universities examined energy drink consumption and nutrition knowledge, comparing these factors with GPA and team to determine the association between student athlete knowledge and practices. The results included a negative correlation between energy drink use and nutrition knowledge, and also between energy drink use and GPA [31]. Barrack et al. found that nearly half of a group of 557 NCAA DI athletes reported habitual supplement use [32]. It is estimated that 12–58% of all dietary supplements marketed for sport and exercise performance may contain ingredients prohibited by the World Anti-Doping Code (WADC) which may lead to halted sport participation [38]. Osterman et al. surveyed 307 male and female NCAA DI athletes about supplement knowledge needs, and found that athletes with the least perceived knowledge were more likely than those with greater perceived knowledge to list a question related to supplement quality or composition (p = 0.030) [39].

Few studies to date have directly assessed the efficacy of the sports RD in the collegiate setting, particularly randomized control trials with an analysis of causal relationships (Table 2). Rossi et al. performed a matched control study with D1 baseball players. Participants were given a sports nutrition education intervention (SNEI) and compared to position-matched teammates. They found that intakes of kilocalories, protein, and carbohydrates increased significantly (p < 0.001) post-nutrition intervention in the SNEI group though body weight increases were similar between groups. In the intervention group, body fat percentage decreased significantly (p = 0.010), while the control group had a nonsignificant increase. The only performance outcome improved by the intervention was the 5-10-5 shuttle test (p = 0.030). This study showed an overall body composition improvement and a single performance outcome improvement when implementing an off-season nutrition intervention [33].

Both coaches and athletes are often unaware of the inadequate calorie and macronutrient intakes that are common among female athletes [11]. Valliant et al. reported findings in which volleyball players received individualized nutrition education from a sports RD over a four-month period, with a focus on increasing the knowledge of types and amounts of foods specific to personal dietary needs and activity level. The athletes completed a sports nutrition knowledge survey at the beginning and end of the intervention. Data from the non-intervention period indicated that athletes did not meet the recommended energy requirement of 37–41 kcal/kg. At the start of the intervention season, the participants consumed 56% of their estimated energy needs, with a range of 25–88%. At the end of the intervention season, the average intake rose to 70% with a range of 44–95%, representing a significant improvement (p = 0.002). The team’s average carbohydrate intake also fell short of the recommended 6–10 g/kg, with an average of 48% of estimated needs at the beginning of the intervention season, and a range of 29–76%. After the intervention, the average carbohydrate intake rose to 66% with a range of 33–101%, a significant improvement (p = 0.010). The average protein intake at the beginning of the intervention season was 59% of the estimated needs, with a range of 16–88%; at the end, it improved significantly (p = 0.010) to 72% of needed protein with a range of 37–102%. Nutrition knowledge improved significantly across the intervention (p = 0.001), with every participant answering more questions accurately on the post-test than they did on the pre-test. The mean scores were 24.7 (±5.9) for the pre-test and 31.5 (±6.1) for the post-test, out of a possible 55 points [8].

In a case study of a DI track and field female athlete, nutrition counseling was shown to positively affect aspects of the female athlete triad. The athlete presented with an energy deficit and menstrual dysfunction while showing continued weight loss prior to the nutrition program. After the one-month nutrition counseling program, weight loss stopped, body fat percentage increased, and performance was not negatively impacted over a 16-month follow up period [34].

At two universities that employed sports RDs, 383 student athletes were surveyed about their sports nutrition knowledge and habits, as well as about their primary source of nutrition information. When student athletes indicated the sports RD as their primary source, they demonstrated a greater understanding of nutrition periodization (47.12% vs. 32.85%), were more likely to consume school-provided boxed meals while on team trips (21.29% vs. 6.77%) and were less likely to consume fast food while on the road (9.90% vs. 19.55%). It was also noted that female athletes tended to eat more nutritiously than male athletes—they were more likely to prepare their own meals, eat breakfast 7 days a week, and consume school-provided boxed meals while on team trips. Male athletes, on the other hand, ate more fast food and restaurant meals, and had more frequent and higher weekly alcohol intake during their competitive seasons [1].

One study investigated nutrition behaviors in NCAA DI baseball players from three universities. Two universities employed a full-time sports RD (schools 1 and 2), while a third (school 3) had no sports RD on staff. All universities had a Certified Strength and Conditioning Specialist (CSCS) on staff, who tended to serve as the primary source of nutrition information at school 3. The majority of athletes sought individual nutrition counseling at schools 1 (61%) and 2 (53%), while those who did not seek personalized assistance utilized team services. Surveys indicated significant differences in dietary habits between student athletes who worked with a sports RD and those who did not. More student athletes from schools 1 and 2 reported never consuming fast food (31% vs. 7%, p = 0.020) or soda on a weekend day (50% vs. 26%, p = 0.080). The RD groups were also more likely to take a multi-vitamin daily (56% vs. 26%, p = 0.020) and consume fast food less frequently on team trips (45% vs. 70%, p = 0.010). The group who primarily received nutrition information from a strength and conditioning coach ate more frequently at hamburger restaurants (21% vs. 6%, p = 0.020), while the schools with a sports RD were more likely to have meals pre-planned when traveling on team trips (48% vs. 13%, p = 0.010). School 3 reported sport coaches who were less aware of healthy food options for the team when traveling (42% vs. 27%, p = 0.050). Regarding nutrient timing, there were also significant differences in responses between groups. Student athletes at schools 1 and 2 found it easier to eat within 1–2 h of activity (92% vs. 67%, p = 0.030), were more likely to have a pre-workout breakfast (67% vs. 38%, p = 0.020), and were more likely to prepare three or more meals on their own each week (86% vs. 74%, p = 0.070). Overall, the availability of a sports RD was correlated with the presence of positive nutritional habits in NCAA DI baseball athletes [35].

Sports RDs do not only have the role of educating student athletes, but they also have a role in training other staff members [36]. Torres-McGehee et al. assessed nutrition knowledge in multiple staff groups as well as with student athletes. They found most collegiate coaches and athletes do not have adequate nutrition knowledge, while some athletic trainers and strength and conditioning specialists may have adequate knowledge. Since these staff groups have daily interactions with the athletes, unlike many sports RDs, the authors discussed how proper nutrition training for all of these groups by a nutrition professional could have a major impact [36]. Evidence suggests that nutrition education programs should be taught by qualified nutrition professionals in order to be effective due to extensive training and knowledge. Zuniga et al. observed that most collegiate athletes use non-nutrition professionals as their sources for nutrition information but would be interested in using mobile applications for nutrition information [37]. These apps could be designed and maintained by nutrition professionals, which would allow for daily interactions by these trained professionals and further increase the use of their services by student athletes.