Associations Between Nutritional Intake, Body Composition, Menstrual Health, and Performance in Elite Female Trail Runners

<b>Background</b>: This study examined nutritional intake, body composition, menstrual health, and performance in elite female trail runners. <b>Methods</b>: A cross-sectional multivariate analysis was conducted on 35 athletes (14 eumenorrheic, 21 amenorrheic/oligomenorrheic). Nutritional intake was assessed through 7-day and 24 h food records; anthropometry followed ISAK standards; performance was evaluated via ITRA and UTMB rankings. Statistical analyses included <i>t</i>-tests, MANCOVA, regression models, and Random Forest, adjusting for body composition and covariates. <b>Results</b>: Although energy availability (EA) did not differ significantly between groups, 94.3% of athletes had clinically low EA (<30 kcal/kg FFM/day). Amenorrheic athletes consumed more simple carbohydrates (21.8 ± 5.7% vs. 17.2 ± 3.1%), protein (2.5 ± 0.6 vs. 1.7 ± 0.2 g/kg/day), fiber, and lipids, while eumenorrheic athletes consumed more complex carbohydrates (129.7 ± 27.0 vs. 82.5 ± 33.3 g/day) and most vitamins. Both groups had inadequate calcium and iron intake. Low EA was moderately associated with an ectomorphic somatotype (r = 0.418). Performance negatively correlated with simple carbohydrates (r = -0.624) and positively with complex carbohydrates, total energy, protein, polyunsaturated fats, and zinc (r = 0.300-0.580). No significant performance differences were found between menstrual status groups. <b>Conclusions</b>: Menstrual irregularities did not affect performance, but nutritional patterns strongly influenced both performance and energy availability. Personalized nutrition strategies are essential for optimizing performance and safeguarding health in elite female trail runners.