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Dietary Supplement Intake and Factors Associated with Increased Use in Preadolescent Endurance Runners

Open AccessPublished:August 02, 2021DOI:https://doi.org/10.1016/j.jand.2021.07.013

      Abstract

      Background

      The prevalence of dietary supplement intake among preadolescent endurance runners is currently unknown.

      Objective

      Our aim was to describe use of dietary supplements, higher-risk supplements, and sport foods among preadolescent endurance athletes and identify associated characteristics of dietary supplement users in this population.

      Design

      This was a retrospective, cross-sectional study.

      Participants/setting

      Participants were 2,113 preadolescent endurance runners (male: n = 1,255, female: n = 858; mean age ± standard deviation = 13.2 ± 0.9 years).

      Main outcome measures

      Use of dietary supplements, higher-risk dietary supplements, and sport foods on 2 or more days per week during the past year.

      Statistical analyses performed

      Mann-Whitney U tests, χ2 tests, univariate and multivariate analyses.

      Results

      Twenty-six percent (n = 551) of preadolescent runners used dietary supplements on 2 or more days per week during the past year; 1.3% (n = 27) reported taking higher-risk supplements. Compared with male runners, female runners reported higher use of 1 or more supplements (32.5% vs 21.7%; P < .001) and 4 or more supplements (4.0% vs 1.9%; P = 0.005), multivitamin/minerals (24.2% vs 14.4%; P < .001), vitamin D (12.4% vs 5.6%; P < .001), calcium (8.9% vs 4.8%; P < .001), iron (3.1 vs 1.1%; P < .001), probiotic supplements (8.2% vs 1.3%; P < .001), and diet pills (0.5% vs 0.0%; P = .02). Male runners reported higher use of creatine (1.3% vs 0.0%; P < .001) and sport foods, including protein bars and drinks (19.5% vs 8.4%; P < .001), energy bars (23.5% vs 9.7%; P < .001), and carbohydrate-electrolyte drinks (27.9% vs 13.3%; P < .001) than female runners. Factors independently associated with a higher likelihood for dietary supplement use included weight loss in the past year, female (vs male) gender, following a vegetarian diet, skipping meals, attempting to gain weight, and history of a running-related bone stress injury.

      Conclusions

      More than one-quarter of preadolescent runners regularly consumed dietary supplements. Behaviors consistent with dietary restriction and history of bone stress injury were associated with higher likelihood for supplement use. Further work to understand supplement use patterns and potential value for nutrition education is advised to optimize health of preadolescent runners.

      Keywords

      Research Question: What is the prevalence of, and what are the characteristics associated with, dietary supplement use among male and female preadolescent endurance runners?
      Key Findings: In this retrospective, cross-sectional investigation of 2,113 preadolescent cross-country runners, 26.1% reported use of 1 or more dietary supplements and 47.2% used either a dietary supplement or sport food on 2 or more days per week during the past year. Compared with male runners, female runners reported higher use of multivitamin/minerals, vitamin D, calcium, iron, probiotic supplements, and diet pills; male runners reported higher use of creatine and sport foods. Factors independently associated with supplement use included weight loss in the past year, female gender, following a vegetarian diet, skipping meals, attempting to gain weight, and history of a running-related bone stress injury.
      Dietary supplements, composed of vitamins, minerals, herbs and botanicals, amino acids, and enzymes, among other nutrients, are products that are intended to supplement the intake of whole foods.
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      Although use of dietary supplements can pose a potential health risk for individuals of any age, it might be of particular concern in youth athletes during times of growth and development. Or and colleagues described 977 adverse events associated with dietary supplements in individuals aged between 0 and 25 years, reported between 2004 and 2015.
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      Taking stock of dietary supplements’ harmful effects on children, adolescents, and young adults.
      In this sample, 24.6% required an emergency department visit or hospitalization and 4.6% resulted in disability or death.
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      Products categorized as “weight loss,” “muscle building,” and “energy” supplements exhibited the strongest associations with a severe medical event.
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      This finding is consistent with health consequences linked to muscle building, weight loss, caffeine-containing preworkout, herbal, and energy supplements noted among youth and young adults in earlier reports.
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      Prevalence and predictors of higher-risk supplement use among collegiate athletes.
      The preadolescent years represent a critical period of growth, including bone mass accrual. These physiological processes require adequate calorie intake, while also meeting requirements for macronutrients, and micronutrients, including calcium and vitamin D. Preadolescent endurance runners are at heightened risk for low energy availability due to demands from both growth and increased energy expenditure from sports participation.
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      A prior investigation among collegiate endurance runners identified a 78.5% prevalence of regular dietary supplement use.
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      • et al.
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      Advancing knowledge of dietary supplement use in preadolescent runners can aid in understanding behavioral patterns to inform future research, with the goal of supporting safe use and the nutritional needs of this population. Therefore, our aim was to describe the use of dietary supplements, higher-risk supplements, and sport foods, and evaluate health factors associated with the intake of these products in a sample of male and female preadolescent endurance runners. We hypothesized that a portion of preadolescent runners would regularly use dietary supplements, and that female runners would use more than male runners. Based on prior research in collegiate endurance runners,
      • Barrack M.T.
      • Fredericson M.
      • Dizon F.
      • et al.
      Dietary supplement use according to sex and triad risk factors in collegiate endurance runners.
      we anticipated that behaviors would be associated with higher likelihood of markers for malnutrition and prior overuse injuries of higher medical concern, including bone stress injury (BSI).

      Materials and Methods

      Study Design and Participants

      This retrospective, cross-sectional study of a convenience sample evaluated results from a web-based, anonymous survey among male and female competitive middle-school cross-country runners from the New England region of the United States. In May 2020, recruitment occurred by utilization of a database including approximately 900 coaches, runners, and parents of middle-school distance runners. Cross-country coaches were also invited to send letters of invitation via e-mail to athletes’ parents. Survey participants received a $5 gift card as an incentive for participation. Runners were included if they participated on a competitive cross-country team during the Fall 2019 season. The study was approved as exempt with a waiver of written parental consent by the Partners Institutional Review Board. Participants provided assent before completing the survey.

      Online Survey

      The web-based study survey was adapted from an assessment tool used in a previously reported investigation of high school endurance runners.
      • Tenforde A.S.
      • Sayres L.C.
      • McCurdy M.L.
      • Sainani K.L.
      • Fredericson M.
      Identifying sex-specific risk factors for stress fractures in adolescent runners.
      Survey questions, managed and administered through the REDCap electronic data-capture software,
      addressed demographic information, weight, height, current training, sports participation history, weekly exercise training, running performance times, dietary patterns, menstrual function (ie, age at menarche, number of menstrual cycles in the past year, loss of 3 or more consecutive menstrual cycles), history of a clinical eating disorder, and injury history. The Eating Disorder Examination Questionnaire Dietary Restraint subscale and pathologic behavior questions were used to evaluate disordered eating.
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      • Crowther J.H.
      The reliability of the Eating Disorder Examination-Self-Report Questionnaire Version (EDE-Q).
      • Mond J.M.
      • Hay P.J.
      • Rodgers B.
      • Owen C.
      • Beumont P.J.
      Validity of the Eating Disorder Examination Questionnaire (EDE-Q) in screening for eating disorders in community samples.
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      • Rickard A.D.
      • De Souza M.J.
      Effect of high dietary restraint on energy availability and menstrual status.
      • Barrack M.T.
      • Rauh M.J.
      • Barkai H.S.
      • Nichols J.F.
      Dietary restraint and low bone mass in female adolescent endurance runners.
      A mean Dietary Restraint subscale score 3.0 or higher was considered elevated.
      • Barrack M.T.
      • Rauh M.J.
      • Barkai H.S.
      • Nichols J.F.
      Dietary restraint and low bone mass in female adolescent endurance runners.
      Body mass index was determined using weight and height and z score and percent-for-age were calculated using Centers for Disease Control and Prevention guidelines and software tool from the Canadian Pediatric Endocrine Group.
      Canadian Pediatric Endocrine Group Calculator
      WHO anthropometric Z-scores 0-19y.
      A BSI was defined as a stress reaction or stress fracture occurring as a result of running and diagnosed by a physician with imaging confirmation (e.g., x-ray, magnetic resonance imaging (MRI), bone scan or computed tomography (CT) scan). A running-related injury (RRI) was defined as a diagnosis of the following: Achilles tendonitis, shin splints, runner’s knee or patellofemoral pain, iliotibial band syndrome, knee injury or anterior cruciate ligament tear, plantar fasciitis, sprained ankle, hamstring strain, Osgood-Schlatter disease, Sever’s disease, or other tendon/bone or joint injury.
      Dietary supplement and sport food use was primarily assessed by 2 questions listed on the study survey. Dietary supplements included vitamin/mineral and nonvitamin/mineral products; sport foods included energy bars, carbohydrate-electrolyte drinks, and protein bars or drinks. One question, evaluating use of vitamins and minerals on 2 or more days per week during the previous year, stated “Please indicate the type(s) of vitamins or mineral you used on two or more days/week over the past year.” Participants were asked to “check all that apply” among a list of vitamins and minerals, including multivitamin/mineral, iron, zinc, vitamin C, vitamin E, magnesium, chromium, B-complex vitamin, or “other.” The second question evaluated use of nonvitamin or mineral supplements and sport foods and stated, “Please indicate if you used any of the supplements [or sports foods] below on two or more days/week over the past year.” Participants selected products from a list including creatine, glutamine, chromium, herb or botanical supplement, amino acid, diet pills, probiotic, energy bar (eg, PowerBar, Clif Bar, and Luna Bar), sport drink (eg, Gatorade and Powerade), protein drink or bar, or “other.” Two additional questions evaluated use of calcium and vitamin D supplements on 2 or more days per week during the past year.
      Survey questions evaluating use of dietary supplements and sport foods were adapted from surveys used to assess supplement and sport food use in collegiate athletes.
      • Sassone J.
      • Muster M.
      • Barrack M.T.
      Prevalence and predictors of higher-risk supplement use among collegiate athletes.
      ,
      • Barrack M.T.
      • Muster M.
      • Nguyen J.
      • Rafferty A.
      • Lisagor T.
      An investigation of habitual dietary supplement use among 557 NCAA Division I athletes.
      Similar survey questions, evaluating supplement use in collegiate athletes exhibited test–retest reliability and face validity, as evaluated by a researcher or sports registered dietitian nutritionist.
      • Barrack M.T.
      • Fredericson M.
      • Dizon F.
      • et al.
      Dietary supplement use according to sex and triad risk factors in collegiate endurance runners.
      ,
      • Barrack M.T.
      • Muster M.
      • Nguyen J.
      • Rafferty A.
      • Lisagor T.
      An investigation of habitual dietary supplement use among 557 NCAA Division I athletes.
      A subset of the analysis addressed use of higher-risk supplements, including preworkout, caffeine-containing, mass-building, weight loss, or those containing herb or botanical ingredients.
      • Sassone J.
      • Muster M.
      • Barrack M.T.
      Prevalence and predictors of higher-risk supplement use among collegiate athletes.
      These supplements were considered “higher risk” due to their potential to include ingredients associated with adverse health effects. Additional evidence linking these supplement types to negative health outcomes has been described previously.
      • Sassone J.
      • Muster M.
      • Barrack M.T.
      Prevalence and predictors of higher-risk supplement use among collegiate athletes.

      Statistical Analysis

      Descriptive statistics (mean ± standard deviation [SD]) and frequencies were used to analyze demographic characteristics. Frequencies also evaluated the proportion of runners reporting use of 1 or more or 4 or more dietary supplements and use of single-nutrient vitamin/mineral supplement, nonvitamin/mineral supplement or sport food on 2 or more days per week during the past year. Mann-Whitney U tests evaluated differences in characteristics for continuous variables (ie, age, eating patterns, running mileage, anthropometric, performance times, BSI history, RRI history, and supplement and sport food use) between male and female runners (reported as mean ± SD). The χ2 analyses evaluated differences between groups for categorical variables, expressed as n (%). Univariate logistic regression analyses evaluated factors (ie, gender, dietary patterns, eating disorder history, and dietary restraint) significantly associated with higher or lower supplement use (odds ratio and 95% CI).
      A multivariate logistic regression model, including factors significantly associated with supplement use from the univariate analyses, evaluated variables significantly and independently associated with supplement use. Due to associations previously reported in the literature between age and supplement use,
      • Barrack M.T.
      • Muster M.
      • Nguyen J.
      • Rafferty A.
      • Lisagor T.
      An investigation of habitual dietary supplement use among 557 NCAA Division I athletes.
      ,
      • Erdman K.A.
      • Fung T.S.
      • Doyle-Baker P.K.
      • Verhoef M.J.
      • Reimer R.A.
      Dietary supplementation of high-performance Canadian athletes by age and gender.
      the multivariate model also included age as a covariate. SPSS, version 26.0,
      conducted all statistical analyses. An α level of .05 was used to determine statistical significance.

      Results

      A total of 2,134 surveys were submitted. Twenty-one respondents did not provide assent (n = 3), left the survey blank (n = 5), or were not in sixth to ninth grade (n = 13), yielding a final sample of 2,113 (n = 1,255 male; n = 858 female) middle school cross-country runners (mean ± SD age = 13.2 ± 0.9 years). Table 1 describes the sample of preadolescent competitive cross-country runners, who were primarily White (79.9%), male (59%), with a mean ± SD body mass index of 19.1 ± 1.4 and mean running mileage of 37.0 km/wk during the fall cross-country competitive season. Five percent of runners reported a history of a physician-diagnosed BSI, 52.5% reported a prior musculoskeletal RRI, and 13.5% reported following a vegetarian diet.
      Table 1Demographic, anthropometric, training, and injury-related characteristics among the total middle school runner sample and according to gender
      CharacteristicMale (n = 1,255)Female (n = 858)Total (n = 2,113)
      mean ± standard deviation
      Age, y13.2 ± 1.013.3 ± 0.913.2 ± 0.9
      n (%)
      Race/ethnicity
      White993 (79.1)695 (81.0)1,689 (79.9)
      Latinx102 (8.1)67 (7.8)169 (8.0)
      Asian/Pacific Islander87 (6.9)64 (7.5)151 (7.1)
      African American70 (5.6)30 (3.5)101 (4.8)
      Grade
      Sixth317 (25.3)185 (21.6)502 (23.7)
      Seventh379 (30.2)258 (30.1)638 (30.2)
      Eighth449 (35.9)360 (42.0)810 (38.3)
      Ninth110 (8.8)55 (6.4)165 (7.8)
      mean ± standard deviation
      Height, cm162.7 ± 8.4161.2 ± 6.3
      P value < .001 between male and female runners, Mann-Whitney U test, χ2 test.
      162.1 ± 7.7
      Weight, kg
      n = 1,958 due to missing data.
      51.2 ± 6.749.4 ± 5.7
      P value < .001 between male and female runners, Mann-Whitney U test, χ2 test.
      50.5 ± 6.4
      BMI
      BMI = body mass index (calculated as kg/m2); n = 1950 due to missing data.
      19.3 ± 1.819.0 ± 1.5
      P value < .001 between male and female runners, Mann-Whitney U test, χ2 test.
      19.2 ± 1.7
      n (%)
      BMI-for-age <5%9 (0.8)9 (1.2)18 (0.9)
      mean ± standard deviation
      Running volume, km/wk
      n = 1942 due to missing data.
      Weekly running volume during the fall cross-country season.
      36.7 ± 11.237.4 ± 11.437.0 ± 11.4
      n (%)
      Vegetarian diet
      Currently following a vegetarian or vegan diet.
      171 (13.7)114 (13.3)285 (13.5)
      Bone stress injury
      History of 1 or more bone stress injuries, diagnosed by a physician.
      48 (3.8)57 (6.7)
      P value < .001 between male and female runners, Mann-Whitney U test, χ2 test.
      105 (5.0)
      Running-related injury
      Prior musculoskeletal running-related injury.
      629 (50.1)481 (56.1)
      P value < .001 between male and female runners, Mann-Whitney U test, χ2 test.
      1,110 (52.5)
      a n = 1,958 due to missing data.
      b BMI = body mass index (calculated as kg/m2); n = 1950 due to missing data.
      c n = 1942 due to missing data.
      d Weekly running volume during the fall cross-country season.
      e Currently following a vegetarian or vegan diet.
      f History of 1 or more bone stress injuries, diagnosed by a physician.
      g Prior musculoskeletal running-related injury.
      z P value < .001 between male and female runners, Mann-Whitney U test, χ2 test.
      Overall, 26.1% of the sample of preadolescent runners reported use of dietary supplements on 2 or more days per week during the past year (Table 2). The Figure provides the frequency of supplement and sport food use in male and female runners and the total sample. Overall, 47.2% (n = 996) of runners reported use of a dietary supplements or sport foods; and 11.5% (n = 243) reported use of both product types on 2 or more days per week during the past year (Figure). Runners with supplement use reported taking a mean ± SD of 1.9 ± 1.4 supplements (median = 1 supplement; range, 1 to 8 supplements) on 2 or more days per week during the past year. Although the majority of runners taking supplements reported use of 1 supplement (n = 307 of 551 [55.7%]), 10.5% (n = 58 of 551) took 4 or more supplements on 2 or more days per week during the past year. A higher proportion of runners taking supplements, compared with those without supplement use, reported use of sport foods among male (56.6% vs 35.9%; P < .001) and female runners (31.9% vs 15.9%; P < .001). Twenty-seven runners (n = 12 female, n = 15 male) reported use of higher-risk supplements; 1 of the 27 runners (female) used 2 higher-risk supplements (herb/botanical and diet pills) (Table 2).
      Table 2Use of dietary supplements, vitamin, and nonvitamin and mineral supplements, and differences between male and female middle school runners
      VariableTotal (n = 2,113)Female (n = 858)Male (n = 1,255)P value
      χ2 test, Mann-Whitney U test.
      Supplement use
      Use of supplements on 2 or more days per week during the past year.
      n (%)
      1 or more supplements551 (26.1)279 (32.5)272 (21.7)<.001
      4 or more supplements58 (2.7)34 (4.0)24 (1.9).005
      mean ± SD
      SD = standard deviation.
      No. of supplements0.5 ± 1.10.7 ± 1.30.4 ± 0.9<.001
      n (%)
      Higher-risk supplements27 (1.3)12 (1.4)15 (1.2).68
      Vitamin/mineral
      Multivitamin/mineral389 (18.4)208 (24.2)181 (14.4)<.001
      Vitamin D176 (8.3)106 (12.4)70 (5.6)<.001
      Calcium136 (6.4)76 (8.9)60. (4.8)<.001
      Iron41 (1.9)27 (3.1)14 (1.1)<.001
      Magnesium11 (0.5)6 (0.7)5 (0.4).35
      Zinc23 (1.1)13 (1.5)10 (0.8).12
      B-complex4 (0.2)2 (0.2)2 (0.2).70
      Vitamin C78 (3.7)35 (4.1)43 (3.4).43
      Vitamin E49 (2.3)24 (2.8)25 (2.0).23
      Nonvitamin/mineral
      Amino acids3 (0.1)0 (0)3 (0.2).15
      Probiotic86 (4.1)70 (8.2)16 (1.3)<.001
      Creatine16 (0.8)0 (0)16 (1.3)<.001
      Glutamine1 (0.0)0 (0)1 (0.1).41
      Herb or botanical24 (1.1)9 (1.0)15 (1.2).76
      Diet pills4 (0.2)4 (0.5)0 (0).02
      Sport foods
      Protein bar or drink317 (15.0)72 (8.4)245 (19.5)<.001
      Energy bar378 (17.9)83 (9.7)295 (23.5)<.001
      Carbohydrate-electrolyte drink464 (22.0)114 (13.3)345 (27.9)<.001
      mean ± SD
      No. of sport foods0.6 ± 0.90.3 ± 0.70.7 ± 1.0<.001
      a χ2 test, Mann-Whitney U test.
      b Use of supplements on 2 or more days per week during the past year.
      c SD = standard deviation.
      Figure thumbnail gr1
      FigureDistribution of preadolescent runners reporting supplement or sport food use; or use of each type.
      Table 2 presents differences in supplement and sport food use between male and female runners. A higher proportion of female, compared to male, runners reported use of 1 or more supplements and 4 or more supplements, as well as a higher number of total supplements (Table 2). In contrast, male runners reported higher use in all sport foods categories, including protein bar and drink, energy bar, carbohydrate-electrolyte drink, more than female runners, as well as a higher total number of sport foods (Table 2). Female runners reported higher use of vitamin and minerals (specifically multivitamins/minerals, vitamin D, calcium, and iron), probiotic supplements and diet pills; male runners reported higher use of creatine than female runners (Table 2).
      Table 3 provides a summary of traits characterizing runners according to dietary supplement use. A higher proportion of runners with supplement use, compared with no supplement use, met criteria for underweight status (body mass index-for-age <5%), had 1 or more prior physician-diagnosed running-related BSIs, followed a vegetarian diet, met criteria for elevated dietary restraint, skipped meals, had history a clinical eating disorder diagnosis, sustained a prior RRI, lost weight in the past year, and reported currently attempting to gain weight (Table 3).
      Table 3Anthropometric characteristics, exercise training, and eating attitudes and behaviors of middle school runners according to supplement use
      Use of supplements on 2 or more days per week during the past year.
      VariableNo supplements (n = 1,562)Supplement use (n= 553)P value
      χ2 test, Mann-Whitney U test.
      Anthropometric
      mean ± standard deviation
      Age, y13.2 ± 0.913.3 ± 1.0.001
      Height, cm162.5 ± 7.4160.8 ± 8.4<.001
      Weight, kg50.8 ± 6.349.4 ± 6.5<.001
      BMI
      BMI = body mass index (calculated as kg/m2).
      19.2 ± 1.419.0 ± 1.8.006
      n (%)
      BMI-for-age <5%7 (0.5)11 (2.3)<.001
      Training
      mean ± standard deviation
      Running volume, km/wk
      Weekly running mileage during the fall cross-country season.
      37.6 ± 11.035.0 ± 12.3.002
      Mile time, min:s6:12 ± 0:366:18 ± 0:42.02
      n (%)
      Bone stress injury
      History of 1 or more bone stress injuries, diagnosed by a physician.
      40 (2.6)65 (11.8)<.001
      Running-related injury791 (50.6)319 (57.9).003
      Eating attitudes and behaviors
      Vegetarian status
      Currently following a vegetarian or vegan diet.
      123 (7.9)162 (29.3)<.001
      mean ± standard deviation
      Dietary Restraint score0.1 ± 0.40.4 ± 0.8<.001
      n (%)
      Elevated Dietary Restraint score
      Mean Eating Disorder Examination Questionnaire Dietary Restraint subscale score >3.0.
      2 (0.1)10 (1.8)<.001
      Skipping meals74 (4.7)76 (13.8)<.001
      Eating disorder
      History of a clinical eating disorder.
      3 (0.2)19 (3.4)<.001
      Attempting weight loss
      Currently trying to lose weight.
      101 (6.5)43 (7.8).29
      Attempting weight gain
      Currently trying to gain weight.
      99 (6.3)56 (10.2).003
      Weight loss past year
      Reported losing weight in the past year; runners with weight loss reported a loss of 2.2 ± 1.3 kg.
      10 (0.6)33 (6.0)<.001
      Weight gain past year
      Reported gaining weight in the past year.
      931 (59.6)269 (48.8)<.001
      a Use of supplements on 2 or more days per week during the past year.
      b χ2 test, Mann-Whitney U test.
      c BMI = body mass index (calculated as kg/m2).
      d Weekly running mileage during the fall cross-country season.
      e History of 1 or more bone stress injuries, diagnosed by a physician.
      f Currently following a vegetarian or vegan diet.
      g Mean Eating Disorder Examination Questionnaire Dietary Restraint subscale score >3.0.
      h History of a clinical eating disorder.
      i Currently trying to lose weight.
      j Currently trying to gain weight.
      k Reported losing weight in the past year; runners with weight loss reported a loss of 2.2 ± 1.3 kg.
      l Reported gaining weight in the past year.
      Table 4 outlines factors associated with dietary supplement use based on univariate analyses and multivariate model. All variables from the univariate analyses were significantly associated with supplement use including older age, identification as female, factors associated with restriction of food intake, vegetarian status, prior injury, or clinical eating disorder history (Table 4). According to the multivariate model, significant factors independently associated with higher likelihood for dietary supplement use included weight loss in the past year, following a vegetarian diet, prior diagnosis of a running-related BSI, skipping meals, and currently attempting to gain weight (Table 4). In addition, according to the model, female runners, compared with male runners, were nearly twice as likely to take dietary supplements on 2 or more days during the past year (Table 4). Weight loss in the past year exhibited the strongest association with supplement use, as those reporting weight loss compared with no weight loss were 7.9 times more likely to report use of all supplements (Table 4).
      Table 4Characteristics of runners associated with dietary supplement use
      Defined as use of supplements on ≥2 days/week over the past year
      evaluated by univariate logistic regression analyses and multivariate model
      Supplement Use n(%)OR (95% CI)p-value
      Univariate
       Age--1.2 (1.1, 1.3)0.001
       Running-related injury
      Prior musculoskeletal running-related injury
      307(28.7)1.3 (1.1, 1.6)0.006
       Attempting weight gain
      Currently trying to gain weight
      56(36.1)1.7 (1.2, 2.4)0.003
       Female279(32.5)1.7 (1.4,2.1)<0.001
       Skipping meals75(50.7)3.2 (2.3, 4.5)<0.001
       Vegetarian diet
      Currently following a vegetarian or vegan diet
      162(56.8)4.8 (3.7, 6.3)<0.001
       BMI-for-age <5%11(61.1)4.9 (1.9, 12.8)0.001
       Bone stress injury
      History of ≥1 bone stress injury, diagnosed by a physician
      78(60.9)5.1 (3.4, 7.7)<0.001
       Weight loss past year
      Reported losing weight in the past year
      33(76.7)9.9 (4.8, 20.2)<0.001
       Dietary restraint
      Mean EDE-Q dietary restraint subscale score >3.0
      10(83.3)14.4 (3.1, 65.8)0.001
       Eating disorder
      History of a clinical eating disorder (AN or EDNOS)
      19(86.4)18.5 (5.5, 62.7)<0.001
      Multivariate
      Nagelkerke R Square= 0.17; the multivariate model was adjusted for all variables listed below “multivariate” and age
      AOR (95% CI)p-value
       Skipping Meals--1.5(1.0, 2.2)0.046
       Attempting weight gain--1.7(1.2, 2.5)0.007
       Female--1.8(1.5, 2.3)<0.001
       Bone stress injury--3.4(2.2, 5.4)<0.001
       Vegetarian diet--4.3(3.3, 5.7)<0.001
       Weight loss past year--7.9(3.7, 16.8)<0.001
      AOR= adjusted odds ratio
      a Defined as use of supplements on ≥2 days/week over the past year
      b Prior musculoskeletal running-related injury
      c Currently trying to gain weight
      d Currently following a vegetarian or vegan diet
      e History of ≥1 bone stress injury, diagnosed by a physician
      f Reported losing weight in the past year
      g Mean EDE-Q dietary restraint subscale score >3.0
      h History of a clinical eating disorder (AN or EDNOS)
      i Nagelkerke R Square= 0.17; the multivariate model was adjusted for all variables listed below “multivariate” and age

      Discussion

      Within our cohort of 2,113 preadolescent endurance runners, 26.1% of the population reported use of dietary supplements on 2 or more days during the past year, and 47.2% used either a dietary supplement or sport food. Supplements taken most frequently included multivitamin/multimineral supplements, vitamin D, calcium, and iron. The independent factors associated with supplement use included weight loss in the past year, following a vegetarian diet, and history of a physician-diagnosed, running-related BSI. These findings represent a novel contribution to the literature; to our knowledge, no prior reports have addressed dietary supplement use and related factors among competitive youth endurance runners.
      Our reported prevalence (26.1%) of supplement use is lower than estimates previously reported in youth athletes and the general population.
      • Stierman B.
      • Mishra S.
      • Gahche J.J.
      • Potischman N.
      • Hales C.M.
      Dietary supplement use in children and adolescents aged </=19 years - United States, 2017-2018.
      ,
      • Nieper A.
      Nutritional supplement practices in UK junior national track and field athletes.
      • O’Dea J.A.
      Consumption of nutritional supplements among adolescents: Usage and perceived benefits.
      • Qato D.M.
      • Alexander G.C.
      • Guadamuz J.S.
      • Lindau S.T.
      Prevalence of dietary supplement use in US children and adolescents, 2003-2014.
      • Parnell J.A.
      • Wiens K.P.
      • Erdman K.A.
      Dietary intakes and supplement use in pre-adolescent and adolescent Canadian athletes.
      This might be related to many of our respondents being younger than athlete respondents from prior investigations, as increasing age has been associated with higher supplement use in athletes.
      • Barrack M.T.
      • Muster M.
      • Nguyen J.
      • Rafferty A.
      • Lisagor T.
      An investigation of habitual dietary supplement use among 557 NCAA Division I athletes.
      ,
      • Erdman K.A.
      • Fung T.S.
      • Doyle-Baker P.K.
      • Verhoef M.J.
      • Reimer R.A.
      Dietary supplementation of high-performance Canadian athletes by age and gender.
      We identified that each year older at time of survey completion was associated with a 20% higher likelihood of supplement use. This study also evaluated supplements based on a specific frequency and time frame, thus representing consistent and prolonged intake compared with general use or use during the previous 30 days.
      • Dwyer J.
      • Nahin R.L.
      • Rogers G.T.
      • et al.
      Prevalence and predictors of children’s dietary supplement use: The 2007 National Health Interview Survey.
      ,
      • Stierman B.
      • Mishra S.
      • Gahche J.J.
      • Potischman N.
      • Hales C.M.
      Dietary supplement use in children and adolescents aged </=19 years - United States, 2017-2018.
      ,
      • Picciano M.F.
      • Dwyer J.T.
      • Radimer K.L.
      • et al.
      Dietary supplement use among infants, children, and adolescents in the United States, 1999-2002.
      ,
      • Sobal J.
      • Marquart L.F.
      Vitamin/mineral supplement use among high school athletes.
      Furthermore, dietary supplements were separated from sport foods; other prior investigations included sport foods in their reported prevalence of supplement users.
      • Erdman K.A.
      • Fung T.S.
      • Doyle-Baker P.K.
      • Verhoef M.J.
      • Reimer R.A.
      Dietary supplementation of high-performance Canadian athletes by age and gender.
      ,
      • O’Dea J.A.
      Consumption of nutritional supplements among adolescents: Usage and perceived benefits.
      ,
      • Parnell J.A.
      • Wiens K.P.
      • Erdman K.A.
      Dietary intakes and supplement use in pre-adolescent and adolescent Canadian athletes.
      In addition, a recent investigation in elite collegiate endurance runners also described a notably higher prevalence of supplement use compared with the present study.
      • Barrack M.T.
      • Fredericson M.
      • Dizon F.
      • et al.
      Dietary supplement use according to sex and triad risk factors in collegiate endurance runners.
      This difference might be related to older age, higher level of competition, or increased accessibility to vitamin or mineral products. Similar to prior reports in children, the most frequently used supplements were multivitamin/mineral products.
      • Stierman B.
      • Mishra S.
      • Gahche J.J.
      • Potischman N.
      • Hales C.M.
      Dietary supplement use in children and adolescents aged </=19 years - United States, 2017-2018.
      ,
      • Qato D.M.
      • Alexander G.C.
      • Guadamuz J.S.
      • Lindau S.T.
      Prevalence of dietary supplement use in US children and adolescents, 2003-2014.
      Female youth runners were more likely to use dietary supplements than male runners. Several prior investigations also report higher use of supplements in female youth athletes.
      • Nieper A.
      Nutritional supplement practices in UK junior national track and field athletes.
      ,
      • Sterlinko Grm H.
      • Stubelj Ars M.
      • Besednjak-Kocijancic L.
      • Golja P.
      Nutritional supplement use among Slovenian adolescents.
      Female runners exhibited higher use of single-nutrient supplements, including calcium and vitamin D, weight-loss supplements (ie, diet pills), multivitamin and mineral supplements, and iron supplements, compared with male counterparts, which is consistent with prior investigations addressing supplement use in youth
      • Qato D.M.
      • Alexander G.C.
      • Guadamuz J.S.
      • Lindau S.T.
      Prevalence of dietary supplement use in US children and adolescents, 2003-2014.
      ,
      • Bell A.
      • Dorsch K.D.
      • McCreary D.R.
      • Hovey R.
      A look at nutritional supplement use in adolescents.
      and collegiate runners.
      • Barrack M.T.
      • Fredericson M.
      • Dizon F.
      • et al.
      Dietary supplement use according to sex and triad risk factors in collegiate endurance runners.
      Our research found no differences in the use of vitamin C, B vitamin complexes, magnesium, zinc, amino acids, glutamine, or supplements containing herbal or botanical ingredients between male and female runners, which is consistent with a prior investigation.
      • Barrack M.T.
      • Fredericson M.
      • Dizon F.
      • et al.
      Dietary supplement use according to sex and triad risk factors in collegiate endurance runners.
      One prior study noted that female adolescents used more B vitamins compared with male adolescent.
      • Qato D.M.
      • Alexander G.C.
      • Guadamuz J.S.
      • Lindau S.T.
      Prevalence of dietary supplement use in US children and adolescents, 2003-2014.
      Male runners in our study population had a higher rate of sport foods and creatine supplement use compared with female runners. Earlier investigations in youth athletes also report higher use of energy drinks and protein bars and drinks in male athletes compared with female athletes.
      • Wiens K.
      • Erdman K.A.
      • Stadnyk M.
      • Parnell J.A.
      Dietary supplement usage, motivation, and education in young, Canadian athletes.
      ,
      • Parnell J.A.
      • Wiens K.P.
      • Erdman K.A.
      Dietary intakes and supplement use in pre-adolescent and adolescent Canadian athletes.
      ,
      • Braun H.
      • Koehler K.
      • Geyer H.
      • Kleiner J.
      • Mester J.
      • Schanzer W.
      Dietary supplement use among elite young German athletes.
      ,
      • Jovanov P.
      • Dordic V.
      • Obradovic B.
      • et al.
      Prevalence, knowledge and attitudes towards using sports supplements among young athletes.
      Higher use of creatine in our sample of male, compared with female, runners is consistent with previous research on general use of creatine more in boys and men.
      • Bell A.
      • Dorsch K.D.
      • McCreary D.R.
      • Hovey R.
      A look at nutritional supplement use in adolescents.
      ,
      • Jovanov P.
      • Dordic V.
      • Obradovic B.
      • et al.
      Prevalence, knowledge and attitudes towards using sports supplements among young athletes.
      • Petroczi A.
      • Naughton D.P.
      The age-gender-status profile of high performing athletes in the UK taking nutritional supplements: Lessons for the future.
      • Butts J.
      • Jacobs B.
      • Silvis M.
      Creatine use in sports.
      In 2020, the US Food and Drug Administration designated creatine monohydrate as “generally recognized as safe” as an ingredient in sport foods. However, limited research has addressed the safety of creatine use in children and adolescents.
      • Or F.
      • Kim Y.
      • Simms J.
      • Austin S.B.
      Taking stock of dietary supplements’ harmful effects on children, adolescents, and young adults.
      ,
      • Butts J.
      • Jacobs B.
      • Silvis M.
      Creatine use in sports.
      ,
      • Kreider R.B.
      • Kalman D.S.
      • Antonio J.
      • et al.
      International Society of Sports Nutrition position stand: Safety and efficacy of creatine supplementation in exercise, sport, and medicine.
      Creatine use has been associated with other substance use, including anabolic steroids in adolescents.
      • LaBotz M.
      • Griesemer B.A.
      Council on Sports Medicine Fitness
      Use of performance-enhancing substances.
      ,
      • Nagata J.M.
      • Ganson K.T.
      • Gorrell S.
      • Mitchison D.
      • Murray S.B.
      Association between legal performance-enhancing substances and use of anabolic-androgenic steroids in young adults.
      In addition, supplement products containing creatine might be subject to contamination or adulteration with other banned substances.
      • Baume N.
      • Mahler N.
      • Kamber M.
      • Mangin P.
      • Saugy M.
      Research of stimulants and anabolic steroids in dietary supplements.
      Further research is needed to examine the use of, and potential risks associated with, creatine in male adolescent and preadolescent runners.
      Factors independently associated with a higher likelihood of supplement use included attempting to gain weight, vegetarian status, history of BSI, skipping meals, and weight loss in the past year. Previous studies have found no associations between supplement use and vegetarian status,
      • Klopp S.A.
      • Heiss C.J.
      • Smith H.S.
      Self-reported vegetarianism may be a marker for college women at risk for disordered eating.
      ,
      • Wirnitzer K.
      • Boldt P.
      • Lechleitner C.
      • et al.
      Health status of female and male vegetarian and vegan endurance runners compared to omnivores-Results from the NURMI Study (Step 2).
      and a different study found that vegetarians do consume more supplements.
      • Steinbach L.
      • Rohrmann S.
      • Kaelin I.
      • et al.
      No-meat eaters are less likely to be overweight or obese, but take dietary supplements more often: Results from the Swiss National Nutrition survey menuCH [published online ahead of print September 7, 2020]. Public Health Nutr.
      Vegetarian or vegan athletes might possibly rely on dietary supplements to limit energy, macronutrient, or micronutrient deficiencies potentially resulting from the exclusion of animal products. A previous investigation among male and female elite collegiate runners also identified associations between BSI and higher supplement use.
      • Barrack M.T.
      • Fredericson M.
      • Dizon F.
      • et al.
      Dietary supplement use according to sex and triad risk factors in collegiate endurance runners.
      It is reasonable that runners with history of BSI would increase supplementation, particularly products containing bone-building nutrients, to support bone health.
      Findings from the current study support associations between higher supplement use and factors consistent with lower food intake or energy deficiency. In the sample, 51% of runners that skipped meals and 77% of runners with weight loss in the past year reported supplement use. This finding suggests that a subset of runners might be using supplements to promote nutrient intake and limiting intake from whole foods. According to a consensus statement from the International Olympic Committee addressing dietary supplements in the high-performance athlete, although dietary supplements can aid in addressing nutrient inadequacies, supplement use should be recommended after undergoing a comprehensive nutritional assessment and coincide with intake of a diet sufficient in energy, macronutrients, and micronutrients. Furthermore, supplement use is associated with potential risk due to the limited regulation of supplements according to the 1994 Dietary Supplement Health and Education Act.
      • Mathews N.M.
      Prohibited contaminants in dietary supplements.
      ,
      • Martinez-Sanz J.M.
      • Sospedra I.
      • Ortiz C.M.
      • Baladia E.
      • Gil-Izquierdo A.
      • Ortiz-Moncada R.
      Intended or unintended doping? A review of the presence of doping substances in dietary supplements used in sports.
      ,
      • Or F.
      • Kim Y.
      • Simms J.
      • Austin S.B.
      Taking stock of dietary supplements’ harmful effects on children, adolescents, and young adults.
      Therefore, it is recommended that youth runners optimize intake of nutrients from whole foods, as the nutrients found in whole foods exhibit interrelated synergy and provide health benefits beyond what is observed for isolated nutrients, as commonly provided by dietary supplements.
      • Jacobs Jr., D.R.
      • Gross M.D.
      • Tapsell L.C.
      Food synergy: An operational concept for understanding nutrition.
      The link between attempting to gain weight and supplement use in the current sample of youth runners suggests that a subset of runners might be taking supplements to support increases in body mass. This finding is consistent with results indicating associations between higher BMI and overall supplement use, and higher-risk supplement use, including mass building and preworkout products among collegiate athletes.
      • Sassone J.
      • Muster M.
      • Barrack M.T.
      Prevalence and predictors of higher-risk supplement use among collegiate athletes.
      ,
      • Barrack M.T.
      • Muster M.
      • Nguyen J.
      • Rafferty A.
      • Lisagor T.
      An investigation of habitual dietary supplement use among 557 NCAA Division I athletes.
      As some supplements promoting weight gain might be considered higher risk, youth runners can benefit from education on dietary strategies for weight gain.
      The prevalence of higher-risk supplement use in the current study was less than the 8.3% prevalence previously identified among collegiate athletes.
      • Sassone J.
      • Muster M.
      • Barrack M.T.
      Prevalence and predictors of higher-risk supplement use among collegiate athletes.
      Although lower, the 1.3% estimate in the middle school runners represents 27 youth taking diet pills (n = 4) or an herb or botanical supplement (n = 24). Some herbal ingredients might promote hepatotoxicity, drug interactions, or contain heavy metals.
      • Saper R.B.
      • Kales S.N.
      • Paquin J.
      • et al.
      Heavy metal content of ayurvedic herbal medicine products.
      ,
      • Voelker R.
      Cardiac patients’ herbal supplement use deserves more careful investigation.
      Weight-loss supplements can also contain harmful ingredients and promote adverse health effects, such as hepatotoxicity or even death. Harmful ingredients have been found in these classes of supplements, such as the drug 2, 4-dinitrophenol, which causes uncoupling of oxidative phosphorylation and has been linked to death.
      • Grundlingh J.
      • Dargan P.I.
      • El-Zanfaly M.
      • Wood D.M.
      2,4-dinitrophenol (DNP): A weight loss agent with significant acute toxicity and risk of death.
      Third-party organizations, such as Consumer Lab, National Sanitation Foundation International,
      National Sanitation Foundation (NSF) International, Certified for Sport Product and Ingredient Certification.
      and United States Pharmacopeia, provide third-party chemical analyses and certification programs to verify supplement dose and ingredients.
      • Marra M.V.
      • Bailey R.L.
      Position of the Academy of Nutrition and Dietetics: Micronutrient supplementation.
      ,
      • Akabas S.R.
      • Vannice G.
      • Atwater J.B.
      • Cooperman T.
      • Cotter R.
      • Thomas L.
      Quality certification programs for dietary supplements.
      The National Sanitation Foundation Certified for Sport program, in particular, evaluates supplements for prohibited substances or masking agents, and serves as the only independent third-party program recognized by the US Anti-Doping Agency and several professional sports organizations aiming to reduce risks associated with dietary supplement use.
      National Sanitation Foundation (NSF) International, Certified for Sport Product and Ingredient Certification.
      The current study is limited by the self-report nature of the web-based survey, which can be subject to recall bias, and thus affect the internal validity of results. Selection bias also represents a potential threat to external validity; however, the large sample supports the generalizability of results. The survey is not validated in this population; no gold standard method to assess this population has been established. We were unable to calculate a survey response rate. The pre-established set of vitamin, mineral, and nonvitamin and mineral supplements listed in the survey questions addressing supplements might have reduced the recall of some supplements. An “other (please specify)” option was included to lower potential underreporting. Despite these limitations, the large sample size and descriptive nature of this report add to the limited knowledge of dietary supplement use health factors that can increase likelihood of dietary supplementation. Our findings help establish that dietary supplement use might be prevalent particularly in preadolescent runners with higher likelihood for health concerns regarding weight management and prior injury.

      Conclusions

      Our report is the first investigation to explore dietary supplement use in preadolescent endurance runners. Twenty-six percent of runners reported taking 1 or more dietary supplements and 47.2% used either a dietary supplement or sport food on 2 or more days per week during the past year. Female runners exhibited higher use of supplements, particularly multivitamins/minerals, calcium, vitamin D, iron, and probiotics, and male runners used creatine and sport foods more frequently. It is recommended that preadolescent endurance runners maximize intake from nutrient-rich whole foods and consume a level of energy that supports their exercise energy expenditure from endurance running. To optimize the health and safety of youth runners, dietary supplementation should, ideally, be considered after a nutrition assessment and with consultation from a registered dietitian nutritionist.

      Acknowledgements

      The authors are appreciative of the middle school runners, coaches, and families for their participation and support for the study.

      Author Contributions

      A. S. Tenforde designed the study. A. S. Tenforde, M. Barrack, and K. E. Ackerman contributed to survey development. A. S. Tenforde and A. C. Wu recruited study participants and collected data. A. S. Tenforde, A. C. Wu, and M. Barrack organized and analyzed the data. M. Barrack, J. Sassone, F. Dizon, and A. S. Tenforde wrote and provided revisions to the manuscript drafts. All authors reviewed, edited, and approved the manuscripts. Michelle Barrack and John Sassone are co-first authors.

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      Biography

      M. Barrack is an associate professor, Department of Family and Consumer Sciences, California State University, Long Beach.
      J. Sassone is a research assistant, Department of Family and Consumer Sciences, California State University, Long Beach.
      F. Dizon is an assistant sports dietitian, Duke University, Durham, NC.
      A. C. Wu is a research assistant, Spaulding Rehabilitation Hospital, Charlestown, MA.
      S. DeLuca is a resident physician in physical medicine and rehabilitation, Spaulding Rehabilitation Hospital, Charlestown, MA, Harvard Medical School, Boston, MA.
      K. E. Ackerman is a physician, Sports Medicine Division, Boston Children’s Hospital, and Neuroendocrine Unit, Massachusetts General Hospital, Boston, MA, and an assistant associate professor of medicine, Harvard Medical School, Boston, MA.
      A. S. Tenforde is a physician, Spaulding Rehabilitation Hospital, Charlestown, MA, and an associate professor of physical medicine and rehabilitation, Harvard Medical School, Boston, MA.