Vitamin/mineral supplement use among high school athletes.

Sobal, Jeffery ; Marquart, Leonard F.

INTRODUCTION

Vitamin and mineral supplements are commonly consumed in the United States with about 35-40% of the general population using them (McDonald 1986; Stewart, McDonald, Levy, Schuker, & Henderson, 1985). Fewer adolescents consume supplements than do adults, with about 20-25% of adolescents using them (Sobal & Muncie, 1988). However, adolescent athletes may be greater consumers of supplements than other groups.

Only four studies provide prevalence data on supplement consumption among high school athletes, reporting that 56% (Douglas & Douglas, 1984), 46% (Parr, Porter, & Hodgson, 1984), 33% (Krowchuk, Anglin, Goodfellow, Stancin, Williams, & Zimet, 1989), and 23% (Moffatt, 1984) used supplements. While three of these studies used large samples of adolescents, the Moffatt (1984) paper was an analysis of 13 elite high school gymnasts. The wide-ranging findings of these studies show that currently there is little consensus about the prevalence of supplement use by high school athletes. Supplement use by high school athletes tends to be lower than that of college and elite athletes (Sobal & Marquart, 1994).

Prior studies of supplement consumption among high school athletes did not examine influences or reasons for use. Other data reveal that boys participating in sports take supplements more often than do boys not involved in athletics (Fleischer & Read, 1982), suggesting that athletic participation may be a motivation for consumption. Alternatively, concern about general health may be a primary motivation. The present investigation examined reasons for supplement use in order to address the importance of motivations based on both athletic performance and health. Influences upon supplement use may originate from health-based sources, such as coaches. The relative importance of these and other influences were examined.

In recent years, women have increased their participation in sports at all levels. Studies of supplement use in the general population (McDonald 1986; Stewart et al. 1985) and among adolescents (Sobal & Muncie, 1988) tend to report that women are more likely to consume supplements than are men. The female gender role is more closely tied to food and nutrition, and supplement use appears to be an expression of these health concerns. The age at which gender differences in supplement consumption begin is not clear. Among athletes supplement use may not follow the gender patterns of the general population, with the emphasis upon athletic performance and competition traditionally more closely related with the male gender role. Existing studies do not analyze gender differences in high school athletes' supplement use (Douglas & Douglas, 1984; Parr et al. 1984; Krowchuk et al., 1989). This investigation examined gender differences in supplement use among adolescent athletes to investigate whether more female-based health roles or more male-based athletic competition roles are more important.

Athletes participate in a variety of sports and have varying aspirations for achievement. Belief that vitamin and mineral supplements enhance athletic performance is common, and athletes often consume supplements as ergogenic aids despite the consensus in the nutrition literature that supplements do not help performance (Haymes, 1991). Athletes who aspire to compete at higher levels of sport may be more likely to use supplements as ergogenic aids because of their athletic ambitions. This study also examined belief about the value of supplements for athletic performance, differences in the consumption of supplements by type of sport, and variations in supplement consumption between high school athletes who plan to compete at the college level and those who do not have higher athletic aspirations.

Prior studies of supplement consumption among medical patients found that those in rural areas were less likely to consume supplements than were their urban or suburban counterparts (Sobal, Muncie, & Guyther, 1986). Many practices, such as health behaviors and techniques for athletic training, may be slower to diffuse into rural areas and be adopted later by rural residents than by those who live in urban settings (Rogers, 1983). This investigation further examined high school athletes in a rural area to provide comparative information with prior studies of adolescents (Douglas & Douglas, 1984; Parr et al., 1984; Krowchuk et al., 1989).

METHOD

A questionnaire was developed based on prior literature on vitamin/mineral supplement consumption (McDonald 1986; Stewart et al., 1985) and the authors' experience in adolescent nutrition and athletics. The questionnaire was pretested on adolescents and examined by professional colleagues for content validity. Demographic questions assessed the athletes' gender, grade in school, sports team participation, major sport, and aspiration to participate in college sports. Supplement use questions asked athletes if they take vitamin/mineral supplements, how often they take them, how long they have been taking them, which of ten supplements they take, the importance of six reasons for using supplements, and to rate the level of influence of seven factors on supplement use. One question asked if they thought taking vitamin/mineral supplements could help athletes perform better in their sport.

The questionnaires were administered by the second author prior to athletic practice during the spring sports season at all nine high schools in one rural county. All questionnaires were completely anonymously, with no names or other identifying information included. Athletes were assured that their coaches would not see the questionnaires. Data were analyzed using a standard statistical package using cross-tabulations with chi square at p [is less than] .05 to determine significant relationships.

RESULTS

A total of 742 athletes completed questionnaires. The majority were boys (58%), although a sizable number of girls were included (42%). Younger athletes were slightly more prevalent, with 27% in ninth grade, 29% in tenth, 24% in eleventh, and 20% in twelfth. Those who expected to participate in college sports included 27% definitely, 23% probably, 36% possibly, and 14% probably not.

A total of 38% of these athletes reported that they took vitamin/mineral supplements. The prevalence of supplement consumption did not differ significantly by gender or grade in school. Athletes who expected to compete in college sports were more likely to use supplements than were their counterparts (p [is less than] .04).

The overall frequency of supplement use was 19% daily, 8% several times per week, 5% several times per month, 9% occasionally during the year, and 61% rarely or never. The duration of time they had been taking supplements was 13% under one year, 12% one to two years, 94% three to five years, 15% over five years, and 52% never. Neither frequency nor duration of supplement use differed significantly by gender, grade, or expected college sport participation.

A variety of supplements were taken by the 39% of athletes who consumed supplements: vitamin C 25% (186), multivitamins 19% (136), iron 11% (83), calcium 9% (64), vitamin A 9% (63), B vitamins 8% (61), vitamin E 8% (55), vitamin D 5% (40), zinc 3% (22), potassium 3% (21), and other supplements 6% (48). (Athletes could check more than one type of supplement they used; thus, percentages add up to over 100%). Girls (16%) more often consumed iron than did boys (8%, p [is less than] .001), and boys (12%) used vitamin A more than did girls (8%, p [is less than] .01), but there were no significant gender differences for the other types of supplements. Younger athletes were more likely to report vitamin D consumption, but there were no other differences by grade. Athletes expecting to participate in college sports more often reported vitamin A use (p [is less than] .001), but there were no other differences by that variable.

Athletes were asked the importance of six reasons for using supplements. Healthy growth was the most important reason for supplement use, followed by treating illness and sports performance. Boys rated muscle development (p [is less than] .04) and sports performance (p [is less than] .03) as being more important than did girls, but there were no other significant gender differences. There were no significant differences in any of these reasons by grade in school. Athletes who expected to participate in college sports cited sports performance as a more important reason for using supplements than did those who did not use them (p [is less than] .05), but there were no significant differences by that variable for any other reasons for supplement consumption.

The importance of seven influences on supplement use are also listed in Table 1. Parents and doctors were the most important influences, distantly followed by coaches. Girls rated parents as more important influences than did boys (p [is less than] .01), while boys rated the importance of coaches (p [is less than] .01) and friends (p [is less than] .01) as greater. There were no other gender differences in these ratings. Younger athletes were less influenced by doctors (p [is less than] .01) and more influenced by television/radio (p [is less than] .01). There were no other grade differences, and none of the influences were significantly associated with plans to participate in college sports.

Table 1
Reasons for Using Vitamin/Mineral Supplements and Influences on Supplement Use
by Adolescent Athletes(*)

Importance of
ReaSons for Use Very Somewhat Not very

Healthy Growth 48% (212) 29% (128) 23% (99)
Preventing Illness 44% (194) 35% (156) 21% (91)
Treating Illness 37% (158) 36% (155) 28% (119)
Sports Performance 31% (137) 34% (150) 34% (149)
Tiredness/Fatigue 28% (118) 32% (137) 40% (171)
Muscle Development 28% (119) 35% (150) 38% (162)

Importance of
Influences Very Somewhat Not Very

Parents 36% (173) 30% (144) 34% (163)
Doctors 26% (122) 28% (130) 46% (213)
Coaches 14% (62) 23% (106) 63% (291)
Friends 10% (44) 17% (80) 73% (336)
Magazines/Papers 9% (40) 22% (101) 70% (322)
Television/Radio 7% (34) 21% (97) 72% (330)
Teachers 4%(17) 16% (73) 80% (365)

* Numbers in the table represent the percentage and N.

When asked if they believed that vitamin/mineral supplement consumption improved athletic performance, 62% replied yes and 38% said no. Boys (66%) were more likely than girls (55%) to state that supplements improved athletic performance (p [is less than] .01). There were no significant differences in this belief by grade or expected involvement in college sports. Athletes who believed supplements improved athletic performance were more likely to consume supplements (50%) than did those who thought supplements were not important (22%, p [is less than] .001). Athletes who believed supplements were important took them more frequently (p [is less than] .001), and had used them for a longer time (p [is less than] .01).

These athletes participated in a wide variety of sports, including many who participated in several sports. Track and field was the most important major sport in this sample, followed by baseball/softball, basketball, football, and soccer. There was considerable variation in supplement use by sport, with the high use of supplements among wrestlers being notable. Frequency of supplement use also varied widely by sport, with wrestlers again being most likely to be frequent supplement users. Duration of supplement use was variable. The belief that supplements improve athletic performance varied among sports, with the highest use among gymnasts and wrestlers.

Table 2
Vitamin/Mineral Supplement use by
Major Sports Represented in High School Athletes

 Major Use Use Use Believe
Major Sport (N) Sport Supps. Daily [less than] year Improve

Track & Field (133) 19% 31% 15% 12% 56%
Baseball/Soft (113) 15% 34/50% 15/28% 14%/21% 59/56
Basketball (91) 13% 40% 19% 10% 72%
Football (83) 11% 39% 22% 17% 64%
Soccer (72) 10% 33% 13% 11% 47%
Wrestling (44) 6% 59% 27% 18% 76%
Lacrosse (36) 5% 25% 8% 3% 59%
Cross Country (36) 5% 47% 18% 10% 69%
Volleyball (23) 3% 44% 23% 10% 70%
Tennis (19) 3% 32% 22% 11% 50%
Ice Hockey (10) 1% 50% 20% 10% 67%
Gymnastics (10) 1% 40% 20% 10% 88%
Skiing (7) 1% 15% 0% 16% 45%
Swimming (4) 1% 25% 0% 0% 25%
Golf (4) 1% 50% 25% 25% 67%
Others (21) 5% 47% 39% 22% 72%

Among these high school athletes in one rural county, only 38% used vitamin/mineral supplements. This is higher than the 25-30% prevalence among other general studies of adolescents (Sobal & Mun-cie, 1988). Supplement use among this rural population was lower than the 56% of athletes who used supplements in the study by Douglas and Douglas (1984) and the 46% reported by Parr et al. (1984). However, it is similar to the 33% prevalence of supplement use found by Krowchuk et al. (1989) and higher than the 23% prevalence among Moffat's (1984) small gymnastics sample. This suggests that rural high school athletes may consume supplements more than do adolescents in general, but may have lower supplement consumption than adolescent athletes in other areas as predicted under a diffusion model (Rogers, 1983).

There were relatively few gender differences in supplement consumption patterns. This is not consistent with the general pattern in the larger population where women use supplements more often than do men (McDonald, 1986; Stewart et al., 1985). The only major gender difference in this study was that boys rated muscle development and sports performance as more important reasons for supplement use than did girls. The athletic performance role among boys may be more important than gender roles in influencing supplement consumption. Athletes who believed supplements improved sports performance were more likely to consume them, use them more frequently, and for a longer period of time. Overall, the linkages of gender roles with health and athletic competition may not be as close as they were in the past.

Patterns of supplement use varied by sport, but the only consistent pattern was that wrestlers were more likely to use supplements and to take them more regularly; 59% of wrestlers used supplements, and 76% believed that they improved performance. This is in line with the high percentage of wrestlers who used vitamin supplements reported by Parr et al. (1984). Wrestlers who restrict food intake may believe that vitamin/mineral supplements provide the necessary nutrients that are lacking due to inadequate food consumption. Supplements may also be used by wrestlers as ergogenic aids to gain a competitive edge over their opponents more often than they are used by athletes in other sports.

From the data about influences upon supplement use, it appears that family and other health-oriented influences are more important in the decision to use supplements than are coaches and sport performance influences. Athletes also ranked health reasons (healthy growth, preventing illness, treating illness) for using supplements as being more important than physical performance variables (sports performance, tiredness/fatigue, muscle development). This supports the view that nonathletic motivations for health most strongly influence adolescent athletes' use of vitamin/mineral supplements.

Some of these athletes had expectations and aspirations to continue their athletic participation at the college level. While those who expected to be involved in college sports more often took supplements, there were few other differences between them and other athletes in patterns of supplement use. This suggests that most of these athletes are not intensively using supplements to prepare themselves for later competition.

Supplements are often used by adolescent athletes as ergogenic aids to improve physical performance. While there are risks associated with vitamin/mineral supplement use, other ergogenic aids such as steroids, amphetamines, and human growth hormone present even greater risks for adolescents involved in athletics. The "stepping-stone" pattern in other types of substance abuse (Taub & Skinner, 1990; Welet & Barnes, 1985) may also occur for ergogenic aids. Such a progression might include athletes who experiment with nutritional supplements as a first step in attempting to enhance performance, and then advance to use more dangerous substances like steroids. Practitioners who work with adolescent athletes may want to look beyond nutritional supplements to assess the use of other substances. Poly-ergogenic aid abuse may include nutritional supplements and other ergogenic substances.

Practitioners who work with adolescent athletes should consider vitamin/mineral supplement consumption in their routine work with that group. It may be valuable to assess supplement use with a vitamin/mineral supplement history (Muncie & Sobal, 1987). Education and counseling can help athletes understand that vitamins and minerals are not in themselves energy producing, but do help to regulate the energy nutrients. This would emphasize the fact that if energy nutrients are lacking in the diet, performance levels will suffer whether or not vitamin/mineral supplements are consumed. Supplements are of limited value to the well-nourished athlete (Haymes, 1991). Athletes who believe that vitamin/mineral supplementation enhances performance may be motivated to improve their nutritional practices once they have a better understanding of the relationship between food, energy, vitamins, minerals, and physical performance.

Overall, vitamin/mineral supplement consumption among these rural high school athletes was not high, but was lower than indicated in most other data about high school athletes, and higher than in other studies of adolescents. However, nutrition education about supplement consumption would be appropriate for some of the athletes, particularly for those who were taking single supplements. This is especially true for the 64 who reported taking vitamin A because of the risk of hypervitaminosis of that vitamin. Excess vitamin A consumption is a risk of particular concern, and has been reported as a problem in athletes (Fumich & Essig, 1983).

Limitations of the study included the use of self-report data, assessment of athletes in only one county, and examination of only high school athletes. Future research should examine supplement use by other groups of high school athletes, as well as their sources of and information about supplements. There is also a need for a greater understanding by those who work with adolescent athletes of the influences on supplement consumption.

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