High school athletes' practical knowledge on where to find and order third‐party tested nutritional supplements increases after education when compared to a control group.

To promote safe supplement use, athletes are advised to choose third‐party tested (TPT) supplements to minimise doping risk. This study evaluated changes in knowledge on supplements in US high school athletes from a 2‐week online supplement education programme. One group of sophomores (ED, n = 48) completed a Canvas course on safe supplement use, based on the Theory of Planned Behaviour, while the other group of freshmen (NOED, n = 38) did not. Participants completed questionnaires pre‐ and post‐intervention to assess practical knowledge of finding and ordering TPT supplements, familiarity with World Anti‐Doping Agency (WADA) banned substances and decision‐making in supplement purchasing. Chi‐Square and McNemar tests were applied with significance set at p ≤ 0.05. Pre‐intervention no differences were found between groups (ages 14–17 years, 39.5% female) for any knowledge questions (p = 0.18). Post‐intervention, ED participants were more likely to know where to find (58.3% vs. 39.5%, p = 0.041), and order (62.5% vs. 28.9%, p = 0.001) TPT supplements, and more athletes in ED (72.9%) than NOED (40.0%) reported deciding to purchase supplements themselves (p = 0.015). Parents were less influential in ED (75.0% vs. 92.1%, p = 0.019). Importantly, positive changes over time were larger for ED versus NOED in knowing where to find (28% vs. 13%, p = 0.04) and order (28% vs. 7%, p < 0.001) TPT supplements and WADA familiarity (19% vs. 5%, p = 0.01). Within‐group changes showed ED improved on all practical knowledge questions (p = <0.001–0.008), whereas NOED only increased in knowing where to find TPT supplements (p = 0.003). These findings suggest an online educational programme may enhance practical knowledge of safe supplement use among high school athletes. [ABSTRACT FROM AUTHOR]