Introduction: Iron is essential in athletes’ performance, as it is essential in cellular respiration and metabolism. However, the increased demand for iron due to strenuous and demanding exercise, along with dietary iron insufficiencies, amplifies the risk of iron deficiency and possibly anemia.

Methods: Our study aimed to evaluate the comparative efficacy of oral supplementation with EPO-Boost Natural Blood Builder (EB) and Blood Booster Active 17 (BB) after 10 weeks of programmed training in 32 male CrossFit^® athletes (26.0 ± 5.7 years; 180.3 ± 7.9 cm; 23.9 ± 1.7 kg/m²). Participants were randomized into three groups and received EB, BB, or a placebo (control group: CG), with the same structured training and diet, in a single-blind, placebo-controlled, randomized trial.

Results: Statistically significant differences were found only in serum ferritin (FER) levels (p = 0.015; η²p = 0.326). The CG experienced a 14.33% decrease, the EB group displayed a 3.60% increase, and the BB group showed a 20.22% increase. Although no statistically significant changes were detected in serum iron levels (sFe) (p = 0,383; η²p = 0,032), it is noteworthy that there was a 10.58% decrease in the CG and a 23.76% increase in the BB group. Significant differences were found in iron storage levels in the CG (p = 0,031) throughout the study. In this regard, three CrossFit^® athletes who were categorized with adequate iron levels at the beginning of the intervention shifted to a state of functional iron deficiency at the end of the study. Regarding athletic performance, no statistically significant differences were observed in aerobic (p = 0.483; η²p = 0.072) or anaerobic (p = 0,.83; η²p = 0,035) thresholds between the CG, EB, and BB.

Conclusion: Supplementation with EB and BB improves FER levels and could help prevent iron deficiency, although this does not translate into increased athletic performance.