Use of nutritional supplements by elite Japanese track and field athletes

Prevalence of dietary supplement use among the military population: a systematic review and meta-analysis

OBJECTIVES

The aim of the study was to evaluate widespread dietary supplements (DSs) use among the military population. There is no recent study to comprehensively evaluate the prevalence of DS use among the military population. Therefore, this systematic review and meta-analysis aimed to present an overview and estimate of the overall prevalence of DSs use among the military population.

METHODS

PubMed, Scopus, Web of Science, and Google Scholar databases were searched up to September 2023 using relevant keywords. All original articles written in English evaluating the prevalence of DSs use among the military population were eligible for this study. The risk of bias assessment of the included studies was done using the Joanna Briggs Institute critical appraisal checklist. The meta-analysis was performed utilizing a random-effects model and STATA software.

RESULTS

In total, 32 cross-sectional studies were included in this review. The prevalence rate of DS use in the overall military population was 57% (95% CI: 49-64); this rate was higher in the studies that were carried out in the USA and the studies with a sample size lower than 10,000 members. Eleven studies reported adverse effects (AEs) following DSs use in the military population, the pooled effect size of them was 13.0% (95% CI: 6-20). The most common AEs reported by military personnel were abdominal pain, nausea, vomiting, and diarrhoea, however, they did not include any serious complications.

CONCLUSION

The findings indicate that the prevalence of DSs use among the military personnel was high. Moreover, some studies reported AEs following DSs use such as gastrointestinal symptoms. Promotion of knowledge and informed attitudes regarding the DSs use in the military population could be useful.

Athlete Sleep Screening Questionnaire in Japanese: Adaptation and Validation Study

CONTEXT

General screening methods for athletes are limited. This study aims to analyze the reliability and validity of the Japanese version of the athlete sleep screening questionnaire.

METHODS

In total, 111 female collegiate athletes completed the initial test and retest. The independent variables included the kind of sports of the participants and their athletic level, grade (freshman, sophomore, junior, and senior), and age. The reliability of the questionnaire was assessed using Cronbach's alpha and intraclass correlation coefficients. Athletes competing in team sports and individual sports were compared to evaluate for differences.

RESULTS

A total of 38.7% of athletes had moderate to severe sleep difficulty score. Their Cronbach's alpha for test and retest were .34 and .44, respectively. The intraclass correlation coefficient indicated sufficient internal consistency and test-retest validity. The mean sleep difficulty scores were 7.0 (2.3) and 6.5 (2.1) for test and retest, but no significant difference was observed between the individual and team sport athletes. Results of multivariable regression analysis revealed that having sleep and performance issues during travel was related to sleep difficulty scores (Coef 1.44, P < .01).

CONCLUSIONS

Athletes of all levels have sleep disorders. The Japanese version of athlete sleep screening questionnaire has been validated with sufficient test-retest validity but has poor internal consistency. Thus, although Japanese version of the athlete sleep screening questionnaire is an appropriate questionnaire for assessing sleep disorders in athletes whose primary language is Japanese, future research is needed to optimize the questionnaire accounting for cultural variation.

Enhancing Performance in Young Athletes: A Systematic Review of Acute Supplementation Effects

BACKGROUND/OBJECTIVES

The increasing popularity of acute supplementation among young athletes is concerning, given the limited scientific evidence to guide recommendations specific to this group. Therefore, the aim of this systematic review was to synthesize the available scientific evidence on the acute effects of supplementation in young athletes to understand the impact on physical and cognitive performance.

METHODS

Following pre-registration on INPLASY (INPLASY202310017) and according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, systematic searches of three electronic databases (Web of Science, PubMed, and Scopus) were conducted by independent researchers from inception until July 2024. Only original studies in English that examined the acute effects of supplementation on young athletes' physical and/or cognitive performance, specifically when taken on the same day as exercise (before or during), were included. The risk of bias was individually assessed for each study using the revised Cochrane risk of bias tool for randomized trials (RoB 2.0).

RESULTS

A total of 16 studies were included in the review. A range of ages, participants, sports, and methodological approaches were involved in the studies included in the current review. The studies mainly used carbohydrates, beetroot juice, and sodium citrate, with carbohydrates being the most used acute supplementation. Carbohydrate supplementation enhanced endurance capacity and increased blood glucose, but mixed results were found for anaerobic performance. Mixed results were found for beetroot juice, with one study finding increases in power production. One study used sodium citrate supplementation, with improvements in technical performance observed.

CONCLUSIONS

Since this review identified only three substances meeting our eligibility criteria, further research is needed to confirm the acute effects of supplements in young athletes and to better understand their benefits and limitations. Carbohydrate supplementation shows strong evidence for enhancing endurance performance, particularly during prolonged activities, while sodium citrate appears to support the preservation of skill performance. In contrast, the effects of beetroot juice are less consistent. Additional research is required to confirm the acute effects of supplements like beetroot juice in young athletes.

Junior athletes' nutritional demands: a narrative review of consumption and prevalence of eating disorders

Information regarding the dietary requirements and consumption of young athletes is limited. Hence, the aim of this narrative review is to provide a comprehensive combination of research and review papers on the nutritional status of young athletes aged 5-18 years old, as well as quantitative, qualitative, wholesome foods, food choices, and eating disordered data concerning the dietary requirements for growing young athletes. This study involved systematic searches of electronic databases, including Google Scholar, PubMed, Science Direct, Scopus, and Web of Science. The specific criteria for identifying research papers published in English from July 1980 until May 2024 were included. Only 48 studies out of 1,262 were included in this narrative review. The findings of this study suggest that, compared with adults, junior athletes need a unique approach to meet their dietary needs. Growth, development, and general athletic performance depend on macronutrients, as they are vital nutrients for young active athletes. However, research on enhancing junior athletes' performance is still in progress, and studies on hydration status, and eating disorders are limited.

Knowledge, Prevalence, and Consequences of Dietary Supplements Intake among Iranian Bodybuilders

Background

This study investigated the nutritional knowledge and prevalence of dietary supplements (DSs) among Iranian bodybuilders.

Methods

This cross-sectional research study involved sampling 648 bodybuilding clubs in Iran. A researcher distributed questionnaires among clubs in various regions and analyzed categorical variables, DS, nutritional knowledge, and sports nutrition data from 160 bodybuilders aged 18 and above in Iran. The analysis was conducted using the results obtained from a quantitative questionnaire.

Results

There was a significant relationship between DS use and gender (P = 0.001, r = 0.330, males > females), bodybuilding history (P = 0.045; r = 0.158), and exercise sessions/wk (P = 0.050, r = 0.156). Whey protein (45.6%) and branched-chain amino acid (33.7%), vitamin D (50%), caffeine (34.3%), and generally vitamin C (56.2%) were the most common DS used. The most information sources for bodybuilders regarding DS were fitness coaches (35.6%) and registered dietitians/nutritionists (34.3%). Drug stores (36.7%) and fitness coaches (19.3%) were the most prominent sources for purchasing DS. Increasing performance (54.3%), increasing the need for DS through exercise (53.6%), preventing injury, and improving recovery (36.2%) were the most important reasons to consume DS. Skin problems (21.0%), increased liver enzymes (10.8%), and hair loss (9.4%) were the most common side effects of DS use. Total nutritional knowledge (macronutrients, micronutrients, and sports nutrition) was 58.6%.

Conclusions

This study concluded that fitness coaches and registered dietitians/nutritionists were the most common information sources for bodybuilders. It also revealed a moderate level of nutrition knowledge among bodybuilders. The most commonly used DS were vitamins C, D, and whey protein. Also, gender, bodybuilding history, and exercise sessions had a significant relationship with the prevalence of DS. However, the study also revealed some concerning findings; bodybuilders commonly experienced adverse side effects such as skin rashes, increased liver enzymes, and hair loss.

Prevalence of anemia and iron deficiency and its association with body mass index in elite Japanese high school long-distance runners

OBJECTIVES

Anemia is a common condition in long-distance runners (LDRs). Recently, not only iron deficiency (ID) but also energy deficiency has been considered as a risk factor for anemia in athletes but no evidence has yet been established. The aim of this study was to investigate the prevalence of anemia and ID and the influence of body mass index (BMI) on anemia in high-school LDRs.

METHODS

The participants were 406 male and 235 female elite Japanese LDRs who competed in the All-Japan High-School Ekiden Championship 2019. They submitted their anthropometric data and results of a blood test within five days after the competition. The prevalence of anemia and ID and the influence of BMI on anemia were assessed retrospectively.

RESULTS

Mean hemoglobin concentrations (Hb) were 14.8 ± 0.9 g/dl in males and 13.2 ± 0.9 g/dl in females. The prevalence of anemia (Hb < 14 g/dl in males and < 12 g/dl in females) was significantly higher in males (16.3%) than females (6.4%), but males also showed higher prevalence of non-iron deficiency anemia (NIDA) than females (11.6% and 3.0%, respectively). No significant gender difference was found in the prevalence of iron deficiency anemia (IDA) (4.7% in males and 3.4% in females). ID (serum ferritin level < 25 ng/ml) was significantly more prevalent in females (37.4%) than males (18.5%). A binary logistic regression analysis revealed that low BMI was a contributor to anemia in females (odds ratios: 0.577 (95% CI: 0.369-0.901), p = 0.012).

CONCLUSION

In Japanese high-school LDRs, one in six males was anemic, but most males did not have ID. Conversely, one-third of females were diagnosed with ID. Lower BMI was identified as a risk for anemia in females, suggesting that leanness may also lead to anemia in females.

Snack and Nutrient Intake Status of Top-Level Female University Athletes: A Cross-Sectional Study

Ensuring proper energy, nutrient intake, and sleep is vital for athlete health and competitiveness. Despite previous studies investigating the nutrient intake among top-level collegiate female athletes in Japan, the status of snack consumption remains unclear. This study addressed this gap by surveying 70 top-level female university athletes. The survey included a self-administered diet history questionnaire, a qualitative food intake frequency survey, and a survey on snack and dietary supplement use. The results revealed a low frequency of snack intake (2.1 ± 2.3 days/week), with 55.7% of athletes reporting snack consumption. The energy intake in the snack-intake group was significantly higher than that in the without-snack-intake group (31.5 ± 10.0 vs. 26.6 ± 9.92 kcal/kg of BM, p = 0.047). Similarly, carbohydrate intake was significantly higher in the snack-intake group than in the without-snack-intake group (4.84 ± 1.71 vs. 3.96 ± 1.65 g/kg of BM/day, p = 0.035). However, neither group reached the recommended value of 5-8 g/kg of BM/day during the medium training period. Overall, this study emphasizes inadequate energy intake even among athletes with a high snack intake frequency, highlighting the necessity to enhance overall food consumption and underscoring the importance of nutritional education for incorporating appropriate complementary meals to improve performance.

A Behaviourally Informed Approach to Reducing the Risk of Inadvertent Anti-doping Rule Violations from Supplement Use

For many reasons, athletes' use of supplements is highly prevalent across sports and competitive levels, despite the risk of these products containing a substance on the World Anti-Doping Agency Prohibited List. Contravening anti-doping rules through supplement use could have serious consequences for competitive athletes (e.g., ineligibility from major competitions, loss of medals and funding) due to the principle of strict liability. Indiscriminate supplement use also poses a risk to athlete health. To reduce the possibility of ingesting a supplement containing prohibited substances, independent quality assurance and certification programs have been established (e.g., Informed Sport). However, these programs do not completely eliminate risk, leading to some anti-doping organisations promoting a 'just say no' to supplements stance. Yet, this approach can be problematic as a small number of supplements may be necessary for athletes to consume, in certain situations. Recognising that athletes will continue to use these heavily marketed products, this narrative review describes a theoretically underpinned and systematic approach to preventing inadvertent doping by considering the barriers to and enablers of athlete adherence to risk minimisation supplement use guidelines (RMSUG). By outlining a conceptual shift towards a behaviourally informed approach, this review serves to stimulate the development of multifaceted interventions to prevent inadvertent doping through supplement use. Recognising that risk-minimised supplement use involves a myriad of behaviours, the problem of inadvertent doping through supplement use is framed, and research appraised, through the lens of the Behaviour Change Wheel.

Are Supplements Consumed by Middle-Distance Runners Evidence-Based? A Comparative Study between Level of Competition and Sex

BACKGROUND

Middle-distance running events have special physiological requirements from a training and competition point of view. Therefore, many athletes choose to take sport supplements (SS) for different reasons. To date, few studies have been carried out that review supplementation patterns in middle-distance running. The aim of the present study is to analyze the consumption of SS in these runners with respect to their level of competition, sex and level of scientific evidence.

METHODS

In this descriptive cross-sectional study, data was collected from 106 middle-distance runners using a validated questionnaire.

RESULTS

Of the total sample, 85.85% responded that they consumed SS; no statistical difference was found regarding the level of competition or sex of the athletes. With respect to the level of competition, differences were observed in the total consumption of SS (p = 0.012), as well as in that of medical supplements (p = 0.005). Differences were observed between sexes in the consumption of medical supplements (p = 0.002) and group C supplements (p = 0.029).

CONCLUSIONS

Higher-level athletes consume SS that have greater scientific evidence. On the other hand, although the most commonly consumed SS have evidence for the performance or health of middle-distance runners, runners should improve both their sources of information and their places of purchase.

Athlete Sleep Behavior Questionnaire in Japanese (ASBQ-J): An Adaptation and Validation Study

Purpose

The Athlete Sleep Behavior Questionnaire (ASBQ) is an 18-item self-reported questionnaire that can be used to screen for sleep disorders in athletes and assess environmental, behavioral, and sports-related factors along with sleep disorders. This study aimed to analyze the reliability and validity of the ASBQ translated into Japanese (ASBQ-J).

Patients and Methods

111 female collegiate athletes completed both the initial test and retest. Independent variables were what kind of sports they perform, level as an athlete, grade (freshman, sophomore, junior, senior), and age. The reliability of the survey was assessed using Cronbach's alpha and intraclass correlation, and Pearson's correlation coefficient was calculated to determine the correlation between the total ASBQ scores and three components which were routine/environmental, behavioral, and sports factors.

Results

A total of 37.8% of athletes had ASBQ scores equal or less than 36 indicating good sleep. However, 19.8% of athletes scored more than 42, indicating poor sleep. Cronbach alpha was 0.62 and 0.65 for test and retest, respectively. Intraclass correlation was 0.78 (P < 0.01), indicating sufficient internal consistency and test-retest validity. Mean ASBQ scores were 38.5 ± 5.0 and 37.0 ± 6.5 for test and retest, respectively, and it was not significantly different between the two groups (P = 0.37). The correlation coefficients between the ASBQ-J and component scores were all statistically significant (all P < 0.01).

Conclusion

ASBQ-J is a reliable questionnaire for assessing sleep disorders in athletes whose primary language is Japanese.

Changes of bone turnover markers and testosterone in Japanese male endurance runners: a pilot study

INTRODUCTION

The bone metabolism of male endurance runners during a competitive season has been little studied. Furthermore, Japanese runners have a special competitive season. This study aimed to investigate the change of bone turnover markers (BTMs) and other hormones in Japanese male endurance runners.

MATERIALS AND METHODS

We investigated biochemical markers, bone formation and resorption markers and sex hormones, body composition using dual-energy X-ray absorptiometry (DXA), and training volume during a competitive season. 11 (age: 24.0 ± 4.3 years) Japanese male endurance runners were analyzed in this study. They participated in all measurements three times a year: the baseline (BL), the post-track period (PT), and the road race period (RR).

RESULTS

Fat mass (FM) and percentage of body fat (% body fat) at RR (p = 0.009, p = 0.009) were lower than at BL. Specific bone alkaline phosphatase (BAP) decreased at PT (p = 0.004) and RR (p = 0.004) compared with BL. However, the bone resorption marker did not change. Free testosterone at PT (p = 0.032) was lower than BL. There was no correlation with blood variables and body composition or training volume.

CONCLUSION

BAP and testosterone in Japanese male endurance runners decreased during the competitive season. However, there was no correlation between blood variables and training volume.

Prevalence of Dietary Supplement Use among Athletes Worldwide: A Scoping Review

Athletes represent a major part of dietary supplement users. This scoping review aims to explore the prevalence of dietary supplement use among athletes worldwide, most commonly used supplements, sources of information on dietary supplements and their reasons for use of these supplements. PubMed, CINAHL, MEDLINE, and PsycInfo were searched for original research articles. Studies were included if they involved athletes, identified the prevalence of dietary supplement use, and were published after 2017. A total of 26 articles were reviewed. Prevalence of dietary supplement use varied among articles, but sex-based differences related to the types of used dietary supplements existed. Generally, the findings were consistent in terms of reasons for use and sources of information. Unfortunately, the lack of homogeneity regarding the definition of dietary supplements, definition of use, reporting timeframes, and data collection methods complicates the attempt to compare the findings among studies.

Health status of recreational runners over 10-km up to ultra-marathon distance based on data of the NURMI Study Step 2

Endurance running is well-documented to affect health beneficially. However, data are still conflicting in terms of which race distance is associated with the maximum health effects to be obtained. Therefore, the aim of this study was to compare the health status of endurance runners over different race distances. A total of 245 recreational runners (141 females, 104 males) completed an online survey. Health status was assessed by measuring eight dimensions in two clusters of health-related indicators (e.g., body weight, mental health, chronic diseases and hypersensitivity reactions, medication intake) and health-related behaviors (e.g., smoking habits, supplement intake, food choice, healthcare utilization). Each dimension consisted of analytical parameters derived to a general domain score between 0 and 1. Data analysis was performed by using non-parametric ANOVA and MANOVA. There were 89 half-marathon (HM), 65 marathon/ultra-marathon (M/UM), and 91 10-km runners. 10-km runners were leaner than both the HM and M/UM runners (p ≤ 0.05). HM runners had higher health scores for six dimensions (body weight, mental health, chronic diseases and hypersensitivity reactions, medication intake, smoking habits, and health care utilization), which contributed to an average score of 77.1% (score range 62–88%) for their overall state of health. Whereas 10-km and M/UM runners had lesser but similar average scores in the overall state of health (71.7% and 72%, respectively). Race distance had a significant association with the dimension “chronic diseases and hypersensitivity reactions” (p ≤ 0.05). Despite the null significant associations between race distance and seven (out of eight) multi-item health dimensions, a tendency towards better health status (assessed by domain scores of health) among HM runners was found compared to other distance runners. However, the optimal state of health across all race distances supported the notion that endurance running contributed to overall health and well-being.

Trial registration number: ISRCTN73074080. Retrospectively registered 12th June 2015.

Sport supplements and the athlete's gut: a review

Vigorous or prolonged exercise poses a challenge to gastrointestinal system functioning and is associated with digestive symptoms. This narrative review addresses 1) the potential of dietary supplements to enhance gut function and reduce exercise-associated gastrointestinal symptoms and 2) strategies for reducing gastrointestinal-related side effects resulting from popular sports supplements. Several supplements, including probiotics, glutamine, and bovine colostrum, have been shown to reduce markers of gastrointestinal damage and permeability with exercise. Yet, the clinical ramifications of these findings are uncertain, as improvements in symptoms have not been consistently observed. Among these supplements, probiotics modestly reduced exercise-associated gastrointestinal symptoms in a few studies, suggesting they are the most evidenced-based choice for athletes looking to manage such symptoms through supplementation. Carbohydrate, caffeine, and sodium bicarbonate are evidence-based supplements that can trigger gastrointestinal symptoms. Using glucose-fructose mixtures is beneficial when carbohydrate ingestion is high (>50 g/h) during exercise, and undertaking multiple gut training sessions prior to competition may also be helpful. Approaches for preventing caffeine-induced gastrointestinal disturbances include using low-to-moderate doses (<500 mg) and avoiding/minimizing exacerbating factors (stress, anxiety, other stimulants, fasting). Adverse gastrointestinal effects of sodium bicarbonate can be avoided by using enteric-coated formulations, low doses (0.2 g/kg), or multi-day loading protocols.

Supplement intake in half-marathon, (ultra-)marathon and 10-km runners - results from the NURMI study (Step 2)

The primary nutritional challenge facing endurance runners is meeting the nutrient requirements necessary to optimize the performance and recovery of prolonged training sessions. Supplement intake is a commonly used strategy by elite and recreational distance runners to meet nutritional recommendations. This study was conducted to investigate the patterns of supplement intake among different groups of distance runners and the potential association between supplement intake and sex, age, running and racing experiences.In a cross-sectional design, from a total of 317 runners participating in this survey, 119 distance runners were involved in the final sample after data clearance, assigned into three groups of 10-km runners (n = 24), half-marathoners (n = 44), and (ultra-)marathoners (n = 51). Personal characteristics, training and racing experiences, as well as patterns of supplement intake, including type, frequency, and dosage, were evaluated by questionnaire. Food Frequency Questionnaire was implemented to assess macronutrient intake. ANOVA and logistic regression were used for statistical analysis.While 50 % of total distance runners reported consuming supplements regularly, no differences between distance groups in consumption of carbohydrate/protein, mineral, or vitamin supplements were observed (p > 0.05). In addition, age, sex, running and racing experience showed no significant association with supplement intake (p > 0.05). Vitamin supplements had the highest intake rate in runners by 43 % compared to minerals (34 %) and carbohydrate/protein supplements (19 %).The present findings provide a window into the targeted approaches of long-distance runners as well as their coaches and sport nutrition specialists when applying and suggesting sustainable nutritional strategies for training and competition.Trial registration: ISRCTN73074080. Retrospectively registered 12th June 2015.

Sex Differences in Supplement Intake in Recreational Endurance Runners-Results from the NURMI Study (Step 2)

It has been well-documented that female and male athletes differ in many physiological and psychological characteristics related to endurance performance. This sex-based difference appears to be associated with their nutritional demands including the patterns of supplement intake. However, there is a paucity of research addressing the sex differences in supplement intake amongst distance runners. The present study aimed to investigate and compare supplement intake between female and male distance runners (10 km, half-marathon, (ultra-)marathon) and the potential associations with diet type and race distance. A total of 317 runners participated in an online survey, and 220 distance runners (127 females and 93 males) made up the final sample after a multi-stage data clearance. Participants were also assigned to dietary (omnivorous, vegetarian, vegan) and race distance (10-km, half-marathon, marathon/ultra-marathon) subgroups. Sociodemographic characteristics and the patterns of supplement intake including type, frequency, dosage, and brands were collected using a questionnaire. One-way ANOVA and logistic regression were used for data analysis. A total of 54.3% of female runners and 47.3% male runners reported consuming supplements regularly. The frequency of supplement intake was similar between females and males (generally or across dietary and distance subgroups). There was no significant relationship for sex alone or sex interactions with diet type and race distance on supplement intake (p < 0.05). However, a non-significant higher intake of vitamin and mineral (but not CHO/protein) supplements was reported by vegan and vegetarian (but not by omnivorous) females compared to their male counterparts. In summary, despite the reported findings, sex could not be considered as a strong modulator of supplement intake among different groups of endurance runners.

Supplement Intake in Recreational Vegan, Vegetarian, and Omnivorous Endurance Runners-Results from the NURMI Study (Step 2)

Nutrient deficiency is a common cause of underperformance in endurance athletes, and supplement intake is frequently considered compensatory for vegan and vegetarian athletes specifically. This study aimed to investigate the patterns of supplement intake among vegan, vegetarian, and omnivorous distance (>10 km) runners and its association with age, sex, and race distance. From a total of 317 runners who participated in an online survey, 220 distance runners (mean age: 38.5 years; mean BMI: 21.75 kg/m²) were selected for the final sample after data clearance and assigned to 100 omnivores, 40 vegetarians, or 80 vegans. Sociodemographic information, racing experience, and patterns of supplement intake, including type, frequency, dosage, etc., were collected using a questionnaire. Macronutrient intake was assessed using a food frequency questionnaire. ANOVA and logistic regression were used for data analysis. The prevalence of supplement intake was 51% for total runners and 72% among vegan runners. Age, sex, and race distance had no significant effect on the type of supplement intake (p > 0.05). Compared to omnivores and vegetarians, vegan runners reported consuming more vitamin (but not carbohydrate/protein or mineral) supplements (p < 0.05). Vitamin B₁₂, magnesium, and multivitamin had the most prevalent use amongst micronutrient supplements. This study points to a central role for supplementary nutritional strategies in different groups of distance runners. The present findings may help future investigations by design to identify specific requirements of endurance runners when adhering to specific kinds of diet particularly plant-based diets.