Examining supplement use and sport supplement belief on doping susceptibility: Supplement type and moral identity matter

Evidence shows dietary supplement use is one of the strongest predictors of doping susceptibility and that the relationship is mediated by beliefs about the effectiveness of supplements for performance enhancement. Further evidence shows this indirect relationship is moderated by moral identity. However, other evidence suggests the relationship between supplement use and doping may be stronger in specific categories of supplement. In this study we examined whether the mediating effect of moral identity on the indirect relationship between supplements and doping via supplement beliefs varied across different categories of supplement. Competitive athletes (N = 550; 45.1% male) completed measures of supplement use, sport supplement beliefs, moral identity and doping susceptibility. Supplement use was grouped via factor analysis into three conceptually sound categories based on patterns of use. Supplement use was indirectly related to doping susceptibility for just two categories (‘muscle building’ and ‘stimulants’) and this relationship was moderated by moral identity. No such relationship existed for the third category (‘Wellbeing & Health’). Our results suggest that previously identified positive associations between supplement use and doping may be limited to a particular type of supplement user. Specifically, supplement users who use muscle building and/or stimulant supplements and have strong sport supplement beliefs and low moral identity are more susceptible to doping.