Dietary supplement use has increased significantly over the past decade. The use of supplements among adolescents seems to be influenced by their beliefs and attitudes. The influence of coaches, parents, and athletic trainers also may be important. The purpose of this study was (1) to determine whether attitudes are a better predictor of adolescents' intentions to use dietary supplements than are subjective norms, and (2) to assess the influence of significant others (coaches, parents, and trainers) on attitudes, subjective norms, and intentions among adolescent athletes. Adolescents (N = 1,626) who were enrolled in grades six through twelve in nine public schools completed a self-report questionnaire that measured attitudes, subjective norms, and intentions regarding dietary supplement use. Results indicated that attitudes were a better predictor of intentions to use dietary supplements than were subjective norms. It was also found that trainers had more influence on the attitudes, subjective norms, and inte ntions of adolescents regarding supplement use than did parents and coaches. Implications for prevention are addressed.
Dietary supplement use has been on the rise in the United States (American Dietetic Association, 1994), with sales increasing from $3.3 billion in 1990 to $9 billion in 1997 (Klebnikov & Moukheiber, 1998). It has been estimated that between 42% and 56% of adolescents use dietary supplements (Kim & Keen, 1999; Krumback, Ellis, & Driskell, 1999; Massad, Sheir, Koceja, & Ellis, 1996; Sobal & Marquart, 1994a). Reasons cited for supplement use include improving athletic performance, gaining muscular strength, and increasing energy level (Sobal & Marquart, 1994a). The use of supplements seems to be influenced by beliefs and attitudes; significant others also may be influential.
Only a few studies have assessed these sources of influence on dietary supplement use (Sobal & Marquart, 1994a, 1994b; Marquart & Sobal, 1993; Graves, Farthing, Smith, & Turchi, 1991; Krowchuk, Agnlin, Goodfellow, Stancin, Williams & Zinet, 1989). One study found that 62% of adolescent athletes believed supplements improve performance, with 50% consuming dietary supplements (Sobal & Marquart, 1994b). Another study found that 70% of adolescent athletes believed dietary supplements were effective, 72% felt it was appropriate to use dietary supplements, and 95% believed dietary supplement use presented little or no risk (Krowchuk et al, 1989).
Coaches have been cited as a prime influence in regard to dietary supplement use among adolescents (Douglas & Douglas, 1984; Krowchuk et al., 1989; Sobal & Marquart, 1994b), yet studies have shown that the majority of coaches have no formal training in nutrition (Graves, Farthing, Smith, & Turchi, 1991; Spear, 1994). Spear (1994) found that 32% of coaches in Alabama high schools recommended protein supplementation and had obtained their information from lay health and fitness magazines, 49% did not know the dangerous side effects of supplement use, and 62% instructed their athletes to take vitamin and mineral supplements. Sossin, Gizis, Marquart, and Sobal (1997) found that coaches felt responsible for providing nutrition information, although as a group they scored only 59% on a nutrition knowledge test. Thus, coaches may not be qualified to provide dietary supplement information.
Parents have also been cited as a major influence (Douglas & Douglas, 1984; Krowchuk et al., 1989; Sobal & Marquart, 1994a). Parents seem to influence adolescents' supplement use through conversations about the possible positive effects. Krumback et al. (1999) found that female athletes were most likely to receive dietary supplement information from family members.
Athletic trainers are a third source of influence. Studies have found that trainers are not as influential as coaches and parents, but they are better prepared to give nutritional advice (Graves et al. …