Dietary Supplement Use in CrossFit® and Marathon Participants: Prevalence, Patterns, and Associated Factors

Dietary supplement use is common among athletes, but evidence comparing supplementation patterns across sports with different physiological demands remains limited. This study examined current use of 11 selected dietary supplements in CrossFit® and marathon participants, compared supplement-specific and aggregate use between disciplines, and identified associated factors. A cross-sectional study was conducted in 297 athletes recruited during two national CrossFit® competitions and one national marathon event in Spain. Data were collected through a structured electronic questionnaire and anthropometric assessment. Current use of these supplements, nutritional counseling, dietary pattern, and Exercise Addiction Inventory (EAI) score were assessed. Adjusted binary logistic regression, Poisson regression with robust variance, and negative binomial regression models were applied. Overall, 202 participants (68.0%) reported current use of at least one surveyed supplement. Creatine, protein, and magnesium were the most frequently reported surveyed supplements. Compared with marathon athletes, CrossFit® participants more often reported current use of at least one surveyed supplement and reported a greater number of supplements from the surveyed list. An operational creatine/protein/caffeine grouping was more frequent in CrossFit®, whereas the magnesium/vitamin D/iron/zinc grouping was not independently associated with discipline after adjustment. Sport discipline, nutritional counseling, and EAI score were the most consistent predictors of supplement use, whereas the magnesium/vitamin D/iron/zinc grouping was mainly associated with age, nutritional counseling, EAI score, and BMI. These findings suggest that use of the assessed supplements differs between disciplines, although they should be interpreted within the scope of the selected list of supplements, which did not include the full range of sports foods and fueling products used in these settings.