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Jadwiga Malczewska, Beata Szczepańska, Romuald Stupnicki and Witold Sendecki

The transferrin receptor-ferritin index (sTfR/logFerr) was determined in 131 male and 121 female athletes in order to assess the frequency of iron deficiency (threshold value of that index taken as 1.8). Blood was drawn for determining morphological indices as well as sTfR, ferritin, iron, total iron binding capacity (TIBC), and haptoglobin. A significantly (p < .01) higher incidence of iron deficiency was observed in women (26%) than in men (11%). The iron deficiency was latent, since no subject was found to be anemic. The plasma iron was significantly lower and TIBC higher (p < .001) in both iron-deficient subgroups than in the non-deficient ones. This confirmed the latent character of iron deficiency. Some hematological indices (Hb, MCH, MCHC, MCV) were significantly lower in iron-deficient female athletes than in male athletes, which suggested a more profound iron deficiency in the former. The sTfR/logFerr index might thus be useful in detecting iron deficiency in athletes, especially in those with erythropoiesis disorders, since physical loads may affect the widely used ferritin levels.

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Nenad Ponorac, Mira Popović, Dea Karaba-Jakovljević, Zorislava Bajić, Aaron Scanlan, Emilija Stojanović and Dragan Radovanović

, 2001 ). There are various markers to assess iron status, with serum ferritin, transferrin saturation, and hemoglobin concentration the most commonly used ( Di Santolo et al., 2008 ; Sandström et al., 2012 ). Peeling et al. ( 2007 ) proposed the following to classify the various stages of iron

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Michael J. Ashenden, David T. Martin, Geoffrey P. Dobson, Colin Mackintosh and Allan G. Hahn

The aim of this study was to establish whether extremely low serum ferritin values in female athletes were associated with indications of iron deficiency anemia and whether serum ferritin values were influenced by the type of training or participants' body size. Hematological data collected during 6 years at the Australian Institute of Sport were reviewed to quantify changes in serum ferritin concentration associated with training and to establish whether decrements in serum ferritin were associated with any change in hemoglobin concentration, mean corpuscular volume, or mean corpuscular hemoglobin concentration. Mean serum ferritin concentrations of 7.5 μg ⋅ L−1 were not associated with any indication of iron-deficiency anemia. Serum ferritin declined by approximately 25% with the onset of rigorous daily training (p <.01) whether training was predominantly weight-bearing or non-weight-bearing. Rowers had significantly higher ferritin concentrations than basketball players of similar stature (p = .02). We conclude that considerable background information such as the stage of training, specific sport, and previous blood results should be sought when interpreting serum ferritin concentrations in female athletes.

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Richard D. Telford, Christopher J. Bunney, Edward A. Catchpole, Wendy R. Catchpole, Vicki Deakin, Bon Gray, Allan G. Hahn and Deborah A. Kerr

This investigation aimed to determine whether the physical work capacity of nonanemic athletes could be improved when plasma ferritin concentrations of below 30 nglml were raised at least 15 ng/ml. The experimental group consisted of 15 training athletes, each of whose plasma ferritin concentration was less than 30 ng/ml (mean and SD of 19.8 ±8.4 nglml). In a control group of 16, each was measured with a plasma ferritin concentration of more than 40 ng/ml (mean and SD of 83.3 ±37.6 ngfml). All participated in submaximal and maximal tests for aerobic and anaerobic power. Following iron supplementation, plasma fenitin concentration in each experimental subject increased by at least 15 nglml to more than 30 ng/ml, to a new mean of 46.3 ±15.5 ng/ml. The performance measures were also repeated, but no significant overall effects were associated with the increased plasma ferritin concentrations. These data provide no sound evidence that physical work capacity of athletes is enhanced when plasma ferritin concentrations of around 20 ng/ml are increased by at least 15 ng/ml.

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John J. Lamanca and Emily M. Haymes

To determine the effects of depleted iron stores on endurance performance and blood lactate concentration, eight active women with normal (>26 ng/ml) and eight with low (< I2 nglml) plasma ferritin concentrations were studied while performing a VO2max and an endurance test (80% VO2max) on a cycle ergometer. The low femtin group had significantly lower serum iron concentration and transferrin saturation and higher TIBC than the normal femtin group. Mean VO2max was not significantly different between groups. No significant difference was found in total time to exhaustion during the endurance test for low (23.2 min) and normal (27.0 min) femtin groups; however, the normal femtin group exercised 14% longer. Blood lactate concentrations following the VOzmax and endurance test did not differ significantly between groups. Food diaries revealed lower daily absorbable iron intake by the low femtin group compared to the normal ferritin group. Ferritin concentration was significantly related to absorbable iron (r=.72) and total iron (r=.70) intake. The results suggest that women with depleted iron stores who are not anemic may have less endurance, but do not have higher blood lactate during exercise than women with normal iron stores.

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William A. Braun, Michael G. Flynn, Daniel L. Carl, Kathy K. Carroll, Todd Brickman and Charlie P. Lambert

Iron deficiency may lead to anemia and may result in compromised endurance exercise performance. Iron deficiency has also been reported to adversely affect the immune system and has been associated with attenuation of natural killer cell (NK) activity. This study was conducted to examine the relationship between iron status and NK activity in highly conditioned female athletes. Ten collegiate female swimmers (SWM) and 9 inactive females (SED) participated in this investigation. Resting blood samples were obtained and analyzed for serum iron and ferritin. NK activity (% lysis) was determined using a whole blood method (51Cr release assay). No significant relationship was found between iron and NK activity (r = 0.55, p = .09), nor between serum ferritin and NK activity (r = 0.33. p = .35) for SWM. ANOVA revealed significantly greater NK activity for SWM (51.63 ± 15.79%) versus SED (30.34 ± 13.67%). Serum ferritin levels were not significantly different between SWM (20.38±8.62Ƞg · ml−1) and SED (16.79±10.53Ƞg · ml−1), nor were iron values different between groups (16.54 ± 2.17 μmol · L−1 SWM; 11.92 ± 2.61 μmol · L−1 SED). A significant relationship between iron status and resting immune function could not be established. Exercise training may affect NK activity; however, the influence of iron status on immune function requires further evaluation.

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Brian Dawson, Carmel Goodman, Tanya Blee, Gary Claydon, Peter Peeling, John Beilby and Alex Prins

Non-anemic, iron depleted women were randomly assigned to an injection group (IG) or oral group (OG) to assess which method is more efficient for increasing iron stores over a short time period. IG received a course of 5 × 2 mL intramuscular injections over 10 d, and OG received one tablet daily for 30 d. Fourteen, 21 and 28 d after commencing supplementation, ferritin concentration in OG significantly increased from baseline (means ± standard error: 27 ± 3 to 40 ± 5 to 41 ± 5 to 41 ± 5 µg/L; P < 0.01). Similarly, on days 15, 20, and 28 post the first injection, ferritin concentration in IG significantly increased from baseline (means ± standard error: 20 ± 2 to 71 ± 17 to 63 ± 11 to 63 ± 7 µg/L; P < 0.01), and was also significantly greater than OG at day 15 and 28 (P < 0.05). Iron injections are significantly more effective (both in time and degree of increase) in improving ferritin levels over 30 d than oral tablets.

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Henry N. Williford, Michele Scharff Olson, Robert E. Keith, Jeffrey M. Barksdale, Daniel L. Blessing, Nai-Zhen Wang and Pete Preston

This investigation evaluated the iron and nutritional status of 12 highly trained aerobic dance instructors who did not take iron supplements (ANS) and 8 who did (AS). A control group (C) consisted of 10 age matched controls. The aerobic instructors had exercised for approximately 3.8 days/wk, 56 min/session for the past 7 yrs. There were no significant differences among groups for energy intake, carbohydrate, protein, fat, nonheme iron, heme iron, or total iron intake (excluding supplemental iron). But both exercise groups had lower ferritin values than the control group. There was also a significant difference in mean cell volume (MCV), with both exercise groups having greater values than the control group. There were no differences among groups for serum iron, total iron binding capacity, transferrin saturation, hematocrit, or hemoglobin. One in three aerobic dance instructors had serum ferritin values below 12 μg · L−1. Results indicate that women exercise leaders have iron profiles that are similar to other groups of female athletes. The increased MCV values suggest runners' macrocytosis or an exercise induced macrocytosis.

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Charles R. Pedlar, Gregory P. Whyte, Richard Burden, Brian Moore, Gill Horgan and Noel Pollock

This case study examines the impact of low serum ferritin (sFe) on physiological assessment measures and performance in a young female 1500-m runner undertaking approximately 95–130 km/wk training. The study spans 4 race seasons and an Olympic Games. During this period, 25 venous blood samples were analyzed for sFe and hemoglobin (Hb); running economy, VO2max, and lactate threshold were measured on 6 occasions separated by 8–10 mo. Training was carefully monitored including 65 monitored treadmill training runs (targeting an intensity associated with the onset of blood lactate accumulation) using blood lactate and heart rate. Performances at competitive track events were recorded. All data were compared longitudinally. Mean sFe was 24.5 ± 7.6 μg/L (range 10–47), appearing to be in gradual decline with the exception of 2 data points (37 and 47 μg/L) after parenteral iron injections before championships, when the lowest values tended to occur, coinciding with peak training volumes. Each season, 1500-m performance improved, from 4:12.8 in year 1 to 4:03.5 in year 4. VO2max (69.8 ± 2.0 mL · kg−1 · min−1) and running economy (%VO2max at a fixed speed of 16 km/h; max 87.8%, min 80.3%) were stable across time and lactate threshold improved (from 14 to 15.5 km/h). Evidence of anemia (Hb <12 g/dL) was absent. These unique data demonstrate that in 1 endurance athlete, performance can continue to improve despite an apparent iron deficiency. Raising training volume may have caused increased iron utilization; however, the effect of this on performance is unknown. Iron injections were effective in raising sFe in the short term but did not appear to affect the long-term pattern.

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Kathleen Woolf, Megan M. St. Thomas, Nicole Hahn, Linda A. Vaughan, Amanda G. Carlson and Pamela Hinton

This study examined iron status and nutrient intake in highly active (n = 28; 20 ± 2 yr, ≥12 hr purposeful physical activity per week [PPA/wk]) and sedentary (n = 28; 24 ± 3 yr, ≤2 hr PPA/wk) women. Participants completed a 7-day weighed-food record (energy, protein, fiber, alcohol, and micronutrients), 7-day pedometer/activity log, and fasting blood draw (hemoglobin, hematocrit, red blood cell indices, C-reactive protein, serum iron, percent transferrin saturation, total iron-binding capacity, ferritin, transferrin receptor [sTfR], and sTfR index). Independent-sample t tests and the Mann–Whitney nonparametric test compared mean values between groups. Lower serum ferritin (p = .01) and mean cell hemoglobin (p < .01) concentrations were found in active than in sedentary women. Higher mean sTfR (p = .01) and sTfR index (p < .01) values were found in the active women. No significant differences were found between groups for the other blood markers. Serum ferritin concentrations (storage iron) indicated iron depletion (Stage I) in 21% of active and 18% of sedentary participants. Nonetheless, 50% of active and 18% of sedentary participants were iron depleted as evidenced by the sTfR index (ratio of functional-to-storage iron). Elevated sTfR concentrations (functional iron) were observed in 25% of active and 3% of sedentary participants. Although the active women reported greater iron (p < .01) but similar heme iron intakes, they had higher mean sTfR, higher sTfR index, and lower serum ferritin concentrations than the sedentary women. Assessment of iron status may require measures not commonly used in routine assessments.