Sports Nutrition Knowledge, Information-Seeking Practices, and Supplement Use Among Croatian Gym Users: A Cross-Sectional Study

This cross-sectional study examined the correspondence between objective and self-rated sports nutrition knowledge and its associations with information practices and supplement use. Seven hundred adult gym users residing in Croatia completed an online survey including a study-specific 14-item knowledge index. The median score was 11 of 14 (interquartile range, 9–12). Internal consistency was moderate (KR-20 = 0.703), but scalability was limited (Loevinger’s H = 0.231). Self-rated knowledge was weakly correlated with the score (Spearman’s ρ = 0.129; p < 0.001), and adjusted scores were similar between respondents reporting good and partial knowledge. Selecting scientific articles or PubMed as a main information source was associated with a 0.83-point higher score (95% confidence interval, 0.32–1.35). Among 628 current or previous supplement users, sometimes and always reading labels were associated with 1.86- and 2.05-point higher scores than never reading labels. These associations persisted in bounded-outcome and alternative-adjustment analyses. The overall association with four-level supplement-use status in the full sample was inconclusive (p = 0.095), although regular users scored higher than never-users in an individual nominal comparison. Information practices were associated with performance on the sampled questions, whereas self-ratings provided limited information about tested performance. The study-specific index and cross-sectional design limit conclusions about individual competence and causal relationships.