An investigation of habitual dietary supplement use among 557 NCAA Division I athletes

Abstract

Supplements may expose athletes to dangerous ingredients, banned substances, toxins or contaminants; however, few investigations assess use among collegiate athletes in the U.S.

OBJECTIVE:

This cross-sectional study evaluated habitual dietary supplement intake, defined use ≥2 days/week over the past year, in NCAA Division I athletes.

METHODS:

Male and female members of a NCAA Division I team, at two universities in southern California completed a 13-item survey. Among 705 eligible participants, 596 submitted surveys (84.5% response rate), 557 surveys included complete data. Chi-square (χ²) analyses evaluated differences among athletes based on sex, weight status, year in college, and sport-type. Independent t-test or ANOVA evaluated mean differences for continuous variables.

RESULTS:

A total of 45.2% athletes (n= 252) reported taking supplements (≥2 days/week over the past year). Vitamin/minerals (25.5%, n= 142), protein/amino acids (24.6%, n= 137) were used most frequently. Male, vs. female athletes, took more supplements overall (1.2 ± 0.1 vs. 0.8 ± 0.1, p = 0.004) and indicated higher use of protein/amino acid products (34.2% vs. 13.5%, p<0.005), whereas, females reported higher use of vitamin/minerals (30.5% vs. 21.1%, p< 0.05). Higher supplement use was also reported by athletes with BMI ≥ 30.0 kg/m² (vs. <30 kg/m², 1.9 ± 0.3 vs. 1.0 ± 0.1, p= 0.02), and athletes in ≥3^rd college year (vs. 1^st or 2^nd year, 1.2 ± 0.1 vs. 0.9 ± 0.1, p= 0.03).

CONCLUSIONS:

Nearly half of NCAA athletes reported habitual supplements use, with significant variation in patterns based on sex, sport-type, year in college, and weight status.

INTRODUCTION

A dietary supplement is a product taken by mouth, intended to supplement intake of whole foods. Supplements contain dietary ingredients such as vitamins, minerals, fatty acids, amino acids, herbs/botanicals, and/or natural substances/enzymes, and can be found in a variety of forms (e.g. tablet, powder, capsule, softgel, or liquid). According to the National Health and Nutrition Examination Survey (NHANES), the use of dietary supplement products in the US has gradually increased since the early 1990s, with a current prevalence of over 50% [1, 2]. Prior investigations exhibit higher estimates in athletes. According to a meta-analysis by Knapik et al., 60% of athletes report taking dietary supplements [3].

Vitamin and mineral supplements are used most frequently among athletes and the general population [2, 3]. Athletes often report use of multivitamin/mineral products, vitamin C, calcium, iron, and antioxidant nutrients [3–8]. Investigations among athletes also note use of non-vitamin/mineral products such as caffeine, creatine, protein and amino acid products, including branched-chain amino acids, beta-alanine, Β-Hydroxy Β-methylbutyrate (HMB), fatty acids, or combination products, such as pre-workout supplements [3–5, 9, 10]. Several investigations note that athletes may refer to health professionals (e.g. sports dietitians, physicians, or pharmacists) for information about supplements with lower frequency than other resources, with less education and formal training related to nutrition and supplement use, such as family, friends, teammates, coaches, or the media [6, 11]. This is notable due to the limited level of regulation of dietary supplements in the US, as outlined by the Dietary Supplement and Health Education Act (DSHEA), with potential outcomes that may include the misbranding of supplements or products containing dangerous ingredients, banned ingredients, or misleading claims [12–21].

Despite a significant body of literature addressing supplement use among international elite Olympic and professional athletes, few investigations evaluate supplement use among NCAA collegiate athletes specifically. This is notable as more than 460,000 NCAA collegiate student athletes participate in competitive sport each year [22]. Due to the unique challenges of collegiate athletes, balancing demands of academic and athletic responsibilities, NCAA collegiate athlete supplement use may differ from elite Olympic or professional athletes competing internationally. Furthermore, the few studies that report on dietary supplements in collegiate student athletes in the US are limited due, in part, to their sample size, inconsistencies in the definition of dietary supplement use, and lack of recency [4, 6, 11]. Additional studies evaluating a larger sample of NCAA collegiate athletes, outlining a specific timeframe and frequency of use, are needed in this population.

Therefore, this study aimed to identify the prevalence of and characteristics related to habitual dietary supplement intake, defined as use on ≥2 days/week over the past year, among athletes competing at two NCAA Division I universities and among athletes based on sex, sport type, weight status, and year in college.

MATERIALS AND METHODS

Subjects

Eligible participants of this cross-sectional study included college students who were active members of a NCAA Division I sports team at two universities in urban regions of southern California, including male and female competitors of all university sports at each respective school (i.e. baseball, softball, basketball, volleyball, tennis, golf, water polo, soccer, cross-country, and track and field). This study was reviewed and approved by the university IRB.

Data Collection

One or more trained members of the research team met with NCAA Division I sports teams to administer a 13-item written supplement survey during the annual team compliance meetings. Athletes were provided with information regarding the study, including an information/consent form, which provided details about the study including its purpose, time commitment, procedures, risks and discomforts, and potential benefits. Individuals who decided to participate in this voluntary study completed the written survey, which was provided to all athletes. To optimize confidentiality, and athletes’ security in providing accurate responses, athletes did not provide identifying information on their survey. Athletes were given approximately 10 minutes to answer the survey questions. A detailed description of the study protocol, survey, sample, and sport-type classification criteria has also been noted previously [23].

Instruments

The survey was designed by study researchers and adapted from previous surveys inquiring about supplement use [4, 5, 23, 24]. It consisted of 13 questions (8 multiple choice, 5 short-answer questions), which included seven parts: (a) participant sport and gender; (b) type and frequency of dietary supplement use; (c) source of dietary supplement information; (d) knowledge regarding dietary supplement safety and current NCAA banned substances policies; (e) reasons for consuming supplements; (f) demographics noting current height (inches), weight (lbs.), year in college; and (g) a question regarding supplement information they would like to learn from a health professional. Items (a), (b), (c), (e), and (f) are reported on in the current study.

In the survey, dietary supplements were defined as “products taken to supplement the diet and consumed in the form of a tablet, capsule, softgel, gelcap, liquid, or powder. Ingredients include vitamins, minerals, essential amino acids, creatine, protein powders, fish oil or other fatty acids, herbal ingredients (such as ginseng, ginkgo biloba, echinacea, etc.), or other natural substances (such as quercetin, melatonin, glucosamine, coenzyme Q10, etc).” Athletes were asked to provide the brand and name of all dietary supplement products taken on at least 2 days per week during the past year.

For items (c) and (e), athletes selected one option from a list of responses addressing source(s) of supplement information (e.g. “friends/acquaintances”, “teammates or athletes”, “coaches”, “health professional”, “internet”, “parent, sibling(s), or other family member”, “other”) or motivation(s) for supplement use (e.g. “improve health or improve nutrition intake”, “weight loss”, “weight gain”, “increase athletic endurance”, “increase strength/power”, “improve recovery”, “increase muscle mass”, “lower body fat”, “reduce risk of injury, disease, and/or illness”).

A test-retest reliability analysis was conducted for six closed-ended items including supplement use (Y/N), sources of information, self-perceived knowledge of supplement safety and health effects, self-perceived knowledge of NCAA policies regarding dietary supplements, reasons for supplement use. Mean Spearman’s Rho and Phi-coefficient correlation coefficient for these items was r= 0.90 (range 0.78–1.00, n=23). A researcher/sports RD reviewed the survey for face validity.

Athlete Classifications

Participants were grouped according to their sports-type, weight status, and year in college. Sport-type classifications were based on the energy system(s) utilized for each sport and adapted from criteria used in Froiland et al. [4], including sports that predominantly use the phosphocreatine system (PCr) (golf, baseball, and softball, n= 157), the phosphocreatine system and anaerobic glycolysis energy systems (PCr/AG) (basketball, volleyball, tennis, sprint and field events in track and field, and water polo, n= 313) and the phosphocreatine system, anaerobic system, and aerobic system (PCr/AG/OP) (soccer, middle distance/distance track and field events, and cross country, n= 86).

Body mass index (BMI, kg/m²) was calculated using athletes’ self-reported height and weight. Classification criteria were based on cutoff points, as outlined from the Center for Disease Control (CDC) and the World Health Organization (WHO). While the CDC uses a BMI ≥25 kg/m² as overweight, this may not apply to elite athletes with higher levels of muscle mass [25] Therefore, a BMI cut-off point of 30 kg/m² (BMI <30 kg/m², n= 512; BMI ≥30 kg/m², n= 27) was used for between-group assessments (WHO, 2000; WHO, 2003). Lastly, athletes were classified in one of two groups according to their self-reported year in college (1^st or 2^nd year, n= 272, vs. 3^rd, 4^th, 5^th year or graduate student, n= 284).

Statistical Analysis

The survey responses were coded and data were transferred to the Numbers (Apple Inc.) or Excel (Microsoft Corp.) programs, following each team meeting. Data were analyzed using the Statistical Package for Social Science (SPSS) statistical software, Version 22 (IBM Analytics). Univariate statistics were calculated as frequencies (%) for categorical variables and means and variance for continuous variables. Chi-square (χ²) analysis was used to detect differences between categorical variables (i.e. sex, weight status, year in college, sport-type). Independent t-test or ANOVA were used to evaluate mean differences for continuous variables (presented as mean ± standard error of the mean). Differences were considered significant at p value alpha= 0.05. Univariate linear regression analyses were run and a multivariate regression model was developed to evaluate factors significantly contributing to the number of supplements athletes reported taking on ≥2 days/week over the past year.

RESULTS

While a total of 705 athletes were eligible to participate, 596 submitted surveys, yielding an 84.5% response rate. Findings represent results from 557 athletes who provided complete data for dietary supplement use. The analyzed subjects were evenly distributed by gender and year in school. A majority of these had a BMI of between 18.5–29.9 kg/m² (sample mean BMI <25.0 kg/m²) (Table 1). Over half of these participated in a sport type primarily utilizing the PCr/AG energy systems (Table 1).

Table 1.

Demographic characteristics among the 557 collegiate athletes

Characteristic	N (%)
Gender
Male	298 (53.5)
Female	259 (46.5)
Anthropometric
Height (cm)	178.7 ± 0.5
Weight (kg)	76.2 ± 0.7
BMI (kg/m2)	23.7 ± 0.1
Weight Statusa
BMI < 18.5 kg/m2	9 (1.7)
BMI 18.5–29.9 kg/m2	503 (93.3)
BMI ≥ 30.0 kg/m2	27 (5.0)
Year in schoolb
1st year	147 (26.4)
2nd year	125 (22.5)
3rd year	138 (24.8)
≥4th year	146 (26.3)
Sport-Typeb
PCr	157 (28.2)
PCr/AG	313 (56.3)
PCr/AG/OP	86 (15.5)

^aN= 18 athletes with missing data

^bOne athlete with missing data

Among the sample, 45.2% of athletes (n= 252) reported use of one or more dietary supplements on 2 or more days per week over the past year. The 252 athletes reporting supplement use took an average of 2.3 ± 0.1 supplements (range 1–13 supplements). Seven percent (n=39) and 3.6% (n= 20) of the sample reported use of >3 and >4 supplements, respectively (Figure 1). Among athletes using >3 supplements, the average use, per athlete, was 5.2 ± 0.3 supplements (taken ≥2 days/week over the past year).

Figure 1.

Dietary supplement use among the 557 collegiate athletes, data represents total sample and use by female vs. male athletes, Chi-square test, ^ap<0.005; ^bp<0.05

Vitamin/mineral (25.5%, n= 142) and protein/amino acid (AA) (24.6%, n= 137) supplements were most frequently used, followed by fatty acid (11.7%, n= 65), other (6.6%, n= 37), pre-workout (4.5%, n= 25), and herb/botanical supplements (2.7%, n= 15) (Figure 1).

Table 2 shows specific vitamin and mineral, fatty acid, protein/amino acid, herb/botanical, and “other” supplement use reported by the athletes. The most frequently consumed vitamin/mineral supplements included multivitamin/mineral, vitamin C, and iron products. Common protein/AA supplements were protein powder and creatine. Fish oil was the most frequently used fatty acid. Most herb/botanical and “other” supplements were used with low frequency.

Table 2.

Specific supplements reported within the vitamin/mineral, protein/AA, fatty acid, herb/botanical, and “other supplement” categories

	Female (n= 259)	Male (n= 298)	p-value	Total
Vitamin/Mineral
Multivitamin/mineral	35(13.5)	36(12.1)	0.613	71(12.7)
Vitamin C	17(6.6)	13(4.4)	0.251	30(5.4)
Iron	17(6.6)	6(2.0)	0.007	23(4.1)
Other/unspecified	10(3.9)	6(2.0)	0193	16(2.9)
Calcium	8(3.1)	5(1.7)	0.271	13(2.3)
Magnesium	9(3.5)	1(0.3)	0.005	10(1.8)
Vitamin D	4(1.5)	4(1.3)	0.842	8(1.4)
Biotin	7(2.7)	0(0)	0.004	7(1.3)
Zinc	2(0.8)	5(1.7)	0.339	7(1.3)
Vitamin B12	3(1.2)	2(0.7)	0.543	5(0.9)
Vitamin E	3(1.2)	0(0)	0.062	3(0.5)
Vitamin B-complex	0(0)	3(1.0)	0.105	3(0.5)
Vitamin A	1(0.4)	1(0.3)	0.921	2(0.4)
ZMA	0(0)	2(0.7)	0.187	2(0.4)
Riboflavin	1(0.4)	0(0)	0.283	1(0.2)
Vitamin B6	1(0.4)	0(0)	0.283	1(0.2)
Protein/AAs
Protein powder	30(11.6)	88(29.5)	<0.001	118(21.2)
Creatine	3(1.2)	36(12.1)	<0.001	39(7.0)
BCAAs	5(1.9)	8(2.7)	0.557	13(2.3)
Amino acids	2(0.8)	5(1.7)	0.339	7(1.3)
Glutamine	1(0.4)	6(2.0)	0.086	7(1.3)
Beta alanine	0(0)	2(0.7)	0.187	2(0.4)
Nacetylcysteine	1(0.4)	0(0)	0.283	1(0.2)
Lysine	0(0)	1(0.3)	0.351	1(0.2)
Fatty Acid
Fish oil	19(7.3)	37(12.4)	0.047	56(10.1)
Omega-3	2(0.8)	3(1.0)	0.770	5(0.9)
Fatty acid unspecified	0(0)	2(0.7)	0.187	2(0.4)
Wheat germ oil	1(0.4)	0(0)	0.283	1(0.2)
Flax seed oil	0(0)	1(0.3)	0.351	1(0.2)
Argan oil	1(0.4)	0(0)	0.283	1(0.2)
Herb/Botanical
Echinacea	2(0.8)	1(0.3)	0.483	3(0.5)
Other herb/botanicals	1(0.4)	2(0.7)	0.647	3(0.5)
Ginger	0(0)	2(0.7)	0.187	2(0.4)
Green tea extract	0(0)	1(0.3)	0.351	1(0.2)
Raspberry ketones	1(0.4)	0(0)	0.283	1(0.2)
Garcinia cambogia	1(0.4)	0(0)	0.283	1(0.2)
Cranberry extract	0(0)	1(0.3)	0.351	1(0.2)
Ginseng	1(0.4)	0(0)	0.283	1(0.2)
Turmeric	0(0)	1(0.3)	0.351	1(0.2)
Milk Thistle	0(0)	1(0.3)	0.351	1(0.2)
Garlic	1(0.4)	0(0)	0.285	1(0.2)
Other supplements
Glucosamine	3(1.2)	9(3.0)	0.131	12(2.2)
Melatonin	2(0.8)	5(1.7)	0.339	7(1.3)
CoenzymeQ10	1(0.4)	3(1.0)	0.387	4(0.7)
Probiotics	3(1.2)	0(0)	0.062	3(0.5)
Enzymes	2(0.8)	1(0.3)	0.483	3(0.5)
Methylsulfonylmethane (MSM)	0(0)	2(0.7)	0.187	2(0.4)
Other unspecified	1(0.4)	1(0.3)	0.921	2(0.4)
Caffeine	1(0.4)	0(0)	0.283	1(0.2)
Asthaxin	0(0)	1(0.3)	0.351	1(0.2)
Citric Acid	0(0)	1(0.3)	0.351	1(0.2)

Chi-square analysis

Values represent n(%)

Sex-based differences

Dietary supplement use varied based on sex. While the total proportion of athletes using supplements did not differ significantly between male and female athletes, more male athletes reported use of >3 and >4 supplements (X²= 9.2, X²= 4.5, respectively) (Figure 1). When looking at the average number of supplements taken, males reported higher use (mean number of supplements 1.2 ± 0.1 vs. 0.8 ± 0.1 p = 0.004, males vs. females, respectively).

A higher proportion of female athletes reported use of vitamin/mineral supplements (X²= 6.3), while male athletes reported more frequent use of protein/amino acid supplements (X²= 32.1) (Figure 1). Male athletes also trended toward higher use of fatty acid and pre-workout supplements (Figure 1). When analyzing specific supplements, higher intakes of iron, magnesium, and biotin were reported among females. Male collegiate athletes more frequently used protein powder, creatine, and fish oil (Table 2).

Weight status

Dietary supplement use varied among athletes, based on weight status. While the total proportion of athletes using supplements did not differ between athletes with BMI <30 kg/m² or BMI ≥30 kg/m², more athletes with BMI ≥30 kg/m² reported use of >3 and >4 supplements (X²= 9.5, X²= 4.0, respectively) (Table 3). On average, athletes with BMI ≥ 30.0 kg/m² used more supplements compared to athletes with BMI between 18.5–29.9 kg/m² (1.9 ± 0.3 vs. 1.0 ± 0.1, p= 0.02). A higher proportion of athletes with BMI ≥30 kg/m² also exhibited use of protein/amino acid (X²= 3.9), other (X²= 16.2), and pre-workout (X²= 12.4) supplements (Table 3).

Table 3.

Breakdown of dietary supplement use among the 557 athletes according to weight status, year in college, and sports-type

	BMI <30 (n= 512)	BMI ≥30 (n= 27)	p-value	1st + 2nd year (n= 272)	≥3rd year (n= 284)	p-value	PCr (n= 157)	PCr/AG (n= 313)	PCr/AG/OP (n= 86)	p-value
Supplement Use
≥ 1 supplement	228(44.5)	16(59.3)	0.134	109(40.1)	142(50.0)	0.019	79(31.3)	140(44.7)	33(38.4)	0.192
>3 supplements	33(6.4)	6(22.2)	0.002	14(5.1)	25(8.8)	0.092	11(7.0)	24(7.7)	4(4.7)	0.625
>4 supplements	18(3.5)	3(11.1)	0.047	6(2.2)	15(5.3)	0.057	5(3.2)	14(4.5)	2(2.3)	0.587
Vitamin/Mineral	130(25.4)	8(29.6)	0.623	68(25.0)	74(26.1)	0.775	31(19.7)	88(28.1)	23(26.7)	0.140
Protein/Amino Acid	122(23.8)	11(40.7)	0.047	57(21.0)	80(28.2)	0.048	55(35.0)	72(23.0)	10(11.6)	<0.001
Fatty Acid	59(11.5)	5(18.5)	0.273	26(9.6)	39(13.7)	0.126	23(14.6)	37(11.8)	5(5.8)	0.122
Other	25(4.9)	4(14.8)	<0.026	15(5.5)	13(4.6)	0.613	7(4.5)	17(5.4)	5(5.8)	0.872
Pre-workout	20(3.9)	5(18.5)	<0.001	10(3.7)	15(5.3)	0.361	13(8.3)	12(3.8)	0(0.0)	0.008
Herbs/Botanical	16(3.1)	2(7.4)	0.227	7(2.6)	11(3.9)	0.387	2(1.3)	14(4.5)	2(2.3)	0.158

Chi-square analyses

Values represent n(%)

Year in school

Use of supplements also varied based on year in school. Athletes in their 3^rd year of college or later (compared to 1^st or 2^nd year) exhibited a higher frequency of overall supplement use (X²= 5.5), use of >3 and >4 supplements (X²= 2.8, X²= 3.6, respectively), and use of protein/amino acid supplements (X²= 3.9) (Table 2). Athletes in their 3^rd year of college or later, when compared to the 1^st or 2^nd year, also reported a higher average intake of supplements (1.2 ± 0.1 vs. 0.9 ± 0.1, p= 0.03).

Sports type

Although overall use of supplements did not vary based on sport-type, a higher proportion of athletes in sports primarily utilizing the PCr energy system used protein/amino acid supplements (X²= 17.4) and pre-workout supplements (X²= 9.6) (Table 3).

Motivations

Motivations for supplement use also varied among athletes based on sex, weight status, and sport type. More female athletes reported use of supplements to improve health (X²= 9.8) (Figure 2). A higher proportion of male athletes reported use of supplements for the purpose of increasing strength/power (X²= 41.0), increasing muscle mass (X²=27.0), weight gain (X²=103.1), and improving recovery (X²= 6.6) (Figure 2). A higher proportion of athletes with a BMI <30 kg/m² reported use of supplements to lose weight (X²= 18.2), lose body fat (X²= 19.4), and improve recovery (X²= 6.0) (Table 4). A higher proportion of athletes in sports primarily using the PCr energy system reported use of supplements to increase strength/power (X²= 16.7), increase muscle mass (X²= 25.3), and gain weight (X²=45.7). Sports utilizing the PCr/AG/OP energy systems were associated with the use of dietary supplements for the purpose of increasing athletic endurance (X²=6.0) and reducing the risk of injury/illness (X²=11.6) (Table 4).

Figure 2.

Self-reported motivations affecting dietary supplement use, among total sample and male vs. female athletes; Chi-square test (male vs. female), ^ap<0.005; ^bp<0.05

Table 4.

Motivations to use dietary supplement, sources of information regarding dietary supplements, based on weight status, year in college, & sports-type

	BMI <30 (n= 512)	BMI ≥30 (n= 27)	p-value	1st + 2nd year (n= 272)	≥3rd year (n= 284)	p-value	PCr (n= 157)	PCr/AG (n= 313)	PCr/AG/OP (n= 86)	p-value
Motivations
Improve health	171(34.1)	7(26.9)	0.453	87(32.7)	96(34.4)	0.674	46(29.5)	110(36.3)	27(31.4)	0.31
Increase strength/power	134(26.7)	8(30.8)	0.648	70(26.3)	79(28.3)	0.601	61(39.1)	73(24.1)	15(17.4)	<0.001
Increase muscle mass	113(22.5)	9(34.6)	0.153	59(22.2)	69(24.7)	0.483	58(37.2)	60(19.8)	10(11.6)	<0.001
Weight gain	113(22.5)	3(11.5)	0.188	57(21.4)	63(22.6)	0.746	63(40.4)	50(16.5)	7(8.1)	<0.001
Improve recovery	109(21.7)	11(42.3)	0.015	51(19.2)	69(24.7)	0.118	30(19.2)	74(24.4)	17(19.8)	0.38
Reduce risk of injury/illness	88(17.5)	3(11.5)	0.430	38(14.3)	55(19.7)	0.092	19(12.2)	49(16.2)	25(29.1)	0.003
Increase athletic endurance	62(12.4)	6(23.1)	0.111	33(12.4)	36(12.9)	0.861	17(10.9)	35(11.6)	18(20.9)	0.05
Lower body fat	34(6.8)	8(30.8)	<0.001	14(5.3)	27(9.7)	0.051	13(8.3)	27(8.9)	2(2.3)	0.12
Weight loss	28(5.6)	7(26.9)	<0.001	15(5.6)	20(7.2)	0.467	8(5.1)	22(7.3)	6(7.0)	0.68
Information Sources
Health Professionals	152(29.9)	5(18.5)	0.207	82(30.5)	81(28.5)	0.613	36(23.2)	100(32.1)	28(32.6)	0.12
Internet	131(25.7	10(37.0)	0.194	58(21.6)	87(30.6)	0.015	46(29.7)	82(26.3)	17(19.8)	0.25
Teammates	116(22.8)	7(25.9)	0.706	46(17.1)	82(28.9)	0.001	46(29.7)	57(18.3)	25(29.1)	0.008
Family	100(19.6)	4(14.8)	0.536	61(22.7)	49(17.3)	0.110	33(21.3)	58(18.6)	19(22.1)	0.68
Coaches	80(15.7)	3(11.1)	0.519	41(15.2)	45(15.8))	0.845	9(5.8)	59(18.9)	18(20.9)	<0.001
Friends	60(11.8)	6(22.2)	0.108	23(8.6)	46(16.2)	0.007	27(17.4)	33(10.6)	9(10.5)	0.09

Chi-square analyses

Values represent n(%)

Sources of information

Male, compared to female, athletes were more likely to report using the internet (31.8% vs. 19.8%, p<0.005, X²= 10.3), teammates (27.4% vs. 18.2%, p<0.05, X²= 6.5), and coaches (18.6% vs. 12.0%, p<0.05, X²= 4.5), while a higher proportion of female athletes reported using health professionals (33.7% vs. 26.0%, p= 0.05, X²= 3.9) and family (26.4% vs. 14.2%, p<0.005, X²= 12.8) for information about supplements. A higher proportion of athletes in their 3^rd college year or older sought information from the internet (X²= 5.9), from teammates (X²= 10.8), and friends (X²= 7.4), compared to athletes in their 1^st or 2^nd year of college (Table 4). Athletes in sports utilizing the PCr/AG/OP energy systems (vs. PCr or PCr/AG) were most likely to report coaches as a source of dietary supplement information (X²= 15.8) (Table 4).

Predictors of supplement use

Univariate regression analyses identified gender (B= 0.12, p= 0.005), body mass index (B= 0.18, p< 0.001), year in school (B= 0.05, p= 0.03), and 8 motivations for supplement use (improve health (B= 0.30, p< 0.001), weight gain (B= 0.17, p< 0.001), endurance (B= 0.12, p= 0.005), strength (B= 0.22, p< 0.001), improve recovery (B= 0.26, p< 0.001), muscle mass (B= 0.19, p< 0.001), fat loss (B= 0.25, p< 0.001), reduce risk of injury/illness (B= 0.29, p< 0.001) as predicting the number of dietary supplement products athletes reported taking on 2 or more days per week over the past year. Table 5 outlines results of the multivariate regression model explaining 20% of the variability in the number of supplements used by collegiate athletes. Three motivations athletes reported for taking supplements, BMI, and gender emerged as significant (adjusted for year in school and sport type) (Table 5).

Table 5.

Multivariate regression model assessing factors contributing to the prediction in number of supplements collegiate athletes reported taking on ≥2 days/week over the past year

	B (unstandardized)	95% CI	B (standardized)	p-value	R-square
					0.20
Motivations
Improve health	0.79	0.51, 1.06	0.23	<0.001
Reduce risk of injury/illness	0.86	0.51, 1.22	0.20	<0.001
Improve recovery	0.51	0.20, 0.83	0.13	0.001
Body mass index (kg/m2)	0.07	0.03, 0.11	0.15	<0.001
Gender	0.31	0.05, 0.56	0.10	0.02

Reasons, coded as 0= not indicating the reason; 1= indicating the given reason for supplement use

Body mass index, continuous variable

Gender, coded as 0= female, 1= male

DISCUSSION

To our knowledge, this is the largest study to date evaluating patterns of habitual dietary supplement use among NCAA Division I athletes in the US. A total of 45.2% athletes reported using dietary supplements, including vitamins, minerals, protein/amino acid, fatty acids, herbs/botanical, pre-workout, or other supplements, on ≥2 days/week over the past year. This is lower than prevalence estimates of supplement use from prior investigations among collegiate athletes, which range from 57–89% [3, 4, 6, 8, 11, 26]. The difference may be due to the time frame and frequency specified in the current study. A study from 2004, among 203 collegiate athletes, found that while 61% of athletes currently took a supplement, only 39% reported taking them ≥2 days/week [4]. Similarly, another investigation of 411 Division I collegiate athletes, reported that while 56.7% athletes used supplements, 39% took supplement products on ≥2 days/week [6]. Due to the timeframe specified (i.e. ≥2 days/week over the past year), the 45.2% estimate of dietary supplement use represents regular and consistent use of supplements, which may better reflect potential risk and exposure to dangerous ingredients, misbranded products, or banned substances.

Supplements taken by the collegiate athletes most frequently included vitamin/mineral (25.5% of athletes) and protein/amino acid (24.6% of athletes) products, which is consistent with the findings reported in previous literature [3, 4]. The overall percent of athletes reporting use of vitamin/mineral supplements was lower, while the intake of protein/AA and fatty acids was similar to prior investigations [3–6, 8]. In addition, use of herb/botanical, caffeine, creatine, and “other” supplements were also reported lower in the current study as compared to prior reports [3, 4, 27].

Upon evaluation of supplement categories, male athletes reported higher use of protein/amino acid supplements, whereas female athletes reported higher use of vitamin/mineral supplements. These sex-based differences align with prior findings, such as the meta-analysis by Knapik et al., which reported a higher use of protein supplements in male compared to female athletes [3]. Creatine use was reported more frequently among men vs. women, which parallels prior investigations [4, 27, 28]. As with the current study, higher use of vitamin/mineral supplements in women, overall, has been regularly observed [2, 4, 6, 29], as has iron [3, 6]. However, unlike in the current study, some investigations exhibit higher use of calcium supplements in female vs. male athletes [2, 4, 6, 29].

Athletes in their 3^rd college year or later (vs. 1^st or 2^nd year) revealed a higher proportion of supplement use, which is consistent with Wardenaar et al. reporting higher use of dietary supplements among Dutch athletes, age 21–35y (vs. age 15–20y)[30]. In contrast, Lieberman et al., upon evaluation of college students’ patterns of supplement intake in the U.S, found non-significant differences among older vs. younger college students [31]. Further research is needed to clarify dietary supplement use among collegiate athletes based on year in college.

While total supplement use did not significantly differ among athletes based on their sports type, a higher proportion of athletes in sports emphasizing the PCr energy system used protein/AA and pre-workout supplements. Higher use of pre-workout supplements is of concern, as these products may include potentially dangerous ingredients such as DMAA, BMPEA, or unregulated levels of caffeine.

Athletes with a BMI ≥30 kg/m² exhibited higher use of supplements compared to athletes with a BMI <30 kg/m². The higher proportion of athletes with BMI ≥30 kg/m² acknowledging use of supplements to lose weight and/or lower body fat in the current study explains, at least, in part, their higher supplement use. However, higher BMI levels in male athletes, in particular, may be due to higher levels of muscle mass, vs. excess body fat [25]. This is consistent with the elevated intake of protein/AA (40.7%) and pre-workout (18.5%) supplements among athletes with BMI ≥30 kg/m², as these proportions are higher than any other athlete subgroups evaluated in the current study. Therefore, the group with BMI ≥30 kg/m² may represent a unique population of athletes with a particularly high intake of supplements, including supplement products linked to adverse events (e.g. pre-workout, weight loss, or supplement products promoting muscularity). The multivariate regression model also outlined BMI as an independent predictor of supplements use among the collegiate athlete sample.

Clear differences in the motivations for taking supplements emerged among athletes based on sex and sport-type. While a higher proportion of female athletes reported use of supplements to improve health, motivations among male athletes were more often linked to increasing strength and muscle mass. This may, in part, explain the higher protein and creatine use reported by men, and concur with prior investigations of college athletes conducted within and outside the U.S. [4, 6, 8]. Additionally, the largest proportion of athletes participating in sports emphasizing the PCr energy system, reported use of supplements for weight and muscle gain, and for increasing strength and power. This is not surprising, as performance for exercises using this energy system include short-bouts of high-intensity exercise and, thus, may benefit from higher levels of muscle mass [32]. Athletes involved in sports emphasizing the PCr/AG/OP energy systems more frequently reported taking supplements to increase athletic endurance and reduce risk of injury/illness, a finding consistent with the endurance nature of these sports and their elevated injury risk [33]. Motivations for supplement use, namely the use of supplements to improve health, reduce risk of injury/illness, and improve recovery, also emerged as significant, independent predictors of overall supplement use.

Athletes reported primarily obtaining supplement information from health professionals and the internet. More female athletes acknowledged seeking information from health professionals and family members, while male athletes reported turning to the internet, teammates, and coaches, a finding consistent with Froiland et al. [4]. Interestingly, similar to male athletes, more college athletes in their 3^rd year or later (vs. 1^st or 2^nd year) reported accessing supplement information from the internet, teammates, or friends. As these sources may not provide information that is evidence-based, some college athlete subgroups may be at risk of utilizing unreliable information when making decisions about supplement use.

The current study was limited by the self-report nature of the supplement survey, as athletes may not have been able to recall all supplements taken over the past year. Additionally, several NCAA sports (e.g. football, swim/diving, gymnastics, wresting, rowing) are not represented in the sample, which may affect the generalizability of findings. The level of nutrition support provided to collegiate athletes in the current study (i.e. part-time Sports RD) promotes the generalizability of findings as athletes at a majority of NCAA Division I schools currently do not have access to a full-time sports RD.

CONCLUSION

The current study found that nearly half of the 557 athletes reported use of supplements on ≥2 days/week over the past year. Male, compared to female, athletes exhibited higher use of ≥3 supplements, protein/AA supplements, while females more frequently used vitamin and minerals. BMI ≥30 kg/m², older athlete age (≥3^rd collegiate year), and participation in sports emphasizing the PCr energy system also related to higher supplement use. Sources of supplement information and motivations for use also varied based on athlete subgroups. According to the recent International Olympic Committee (IOC) Consensus Statement on dietary supplements, it is recommended that a trained health professional, such as a registered dietitian nutritionist [34] with a board certification in sports dietetics [34] provide athletes with reliable, evidence-based information about dietary supplements and, after conducting a comprehensive nutrition assessment, provide individualized recommendations [35]. Third-party testing also provides more information about the quantity and quality of supplement ingredients. Together these strategies may optimize collegiate athletes’ awareness and understanding of the risks linked to supplement use and limit potential health or eligibility consequences.