For the evaluation of iron nutrition status, the measurement of serum ferritin levels is the most convenient and widely used technique for estimating stored iron. However, the cut-off value of serum ferritin for iron deficiency in athletes has not yet established. This study aimed to determine the cut-off value of serum ferritin to define iron deficiency in male college student runners. This study included 37-43 Japanese male college student runners for each month. Anthropometric measurements and blood collection were conducted from March to December 2018. In all months except May, significant negative correlations were observed between serum ferritin and transferrin levels, total iron binding capacity (TIBC), and unsaturated iron binding capacity. Furthermore, a significant association between serum ferritin levels and TIBC was observed by nonlinear regression analysis. The curvature radius and curvature were calculated using the data from 9 mo, and serum ferritin levels with the smallest curvature radius and the highest curvature in each month were identified. The serum ferritin levels were as follows: 35.0 ng/mL in March, 45.0 ng/mL in April, 40.0 ng/mL in June, 35.0 ng/mL in July, 35.0 ng/mL in August, 35.0 ng/mL in September, 35.0 ng/mL in October, 35.0 ng/mL in November, and 40.0 ng/mL in December. The average value was 37.2 ng/mL. In conclusion, the cut-off value of serum ferritin for defining iron deficiency in runners was determined to be 40.0 ng/mL in this study. This value (40.0 ng/mL) may be useful for iron deficiency screening in runners.
Keywords: anemia; athlete; iron status; sports; sports nutrition.