Relative Energy Intake as a Determinant of Iron Status in Elite Athletes

Background Iron deficiency is highly prevalent in elite athletes and can impair performance even without anemia. While iron intake is essential, emerging evidence suggests that energy availability can critically affect iron metabolism. This study investigated whether relative energy and nutrient intake predict serum ferritin levels in elite athletes under real-world training conditions. Methods One hundred forty-nine national squad athletes (80 females, 69 males) from nine sports disciplines completed 3-day food protocol, analyzed against individualized recommendations. Iron status was classified by serum ferritin and hemoglobin; fractional absorption was estimated using a predictive model. Multiple linear regression identified predictors of ferritin concentration. Results Most athletes failed to meet recommendations for calories (87%), carbohydrates (95%), and iron (39%). Biochemical iron deficiency (iron depletion or iron-deficient erythropoiesis) was present in 42% of athletes, with a marked female predominance. Relative caloric intake, iron supplementation, and age significantly predicted ferritin concentration (R² = 0.34, p < 0.001), whereas carbohydrate intake and sex showed non-significant trends. Low energy intake was associated with higher risk of iron deficiency and altered absorption profiles. Conclusion Relative energy intake emerged as the strongest determinant of systemic iron availability in elite athletes. Integrated nutrition strategies that address both energy sufficiency and iron intake are essential to prevent subclinical deficiency and sustain high-performance capacity.