The Low Serum Ferritin as an Indicator of Inadequate Nutrition in International-Level Female Swimmer

Introduction: Iron deficiency is a common feature in athletes, and optimizing iron levels may become a contributing factor to improved athletic performance. Purpose: This study aimed to evaluate body iron stores and their relationship with sports performance. It also sought correlations between the swimmers’ hematological, hormonal, anthropometric, and functional status and their sports achievements. Methodology: The research involved 19 athletes (11 women and 8 men) from the Bulgarian national swimming team. They were tested for maximal aerobic capacity on a cycle ergometer and had blood samples taken to determine iron status and hematological and hormonal markers. Their swimming achievements (Swimming points) were evaluated as a percentage of the world records in the respective discipline. Results: There were statistically significant differences between the female and male swimmers for Unbound Iron Binding Capacity (UIBC) and ferritin. A higher UIBC in women indicated lower iron levels in them. Among female swimmers, five had ferritin levels below 40 ng/mL. In women, a highly reliable correlation between the Swimming points and ferritin concentration (r = .68) was observed. All male swimmers had ferritin values above 40 ng/mL, and there was no reliable correlation between ferritin concentration and Swimming points, probably because ferritin was in the optimal range and is no longer a significant performance factor. Conclusions: In swimmers, the optimal serum ferritin concentration is probably in the range of 40–90 ng/mL. Many female swimmers have a relative iron deficiency with sub-optimal ferritin values. In competitive female swimmers, low ferritin level is an indicator of both iron deficiency and inadequate diet. It can be expected that an adequate nutritional regime in athletes with low ferritin values will lead both to the replenishment of iron stores and to an increase in muscle mass and, ultimately, to an improvement in sports performance.