Efficacy of iron supplementation may be misinterpreted using conventional measures of iron status in iron-depleted, nonanemic women undergoing aerobic exercise training

Abstract

Despite its known detrimental effects, iron deficiency remains the most common micronutrient deficiency in the world. Many interventions that aim to improve iron status involve physically active populations. Intense aerobic exercise training negatively affects iron status; however, the impact of regular moderate aerobic exercise on the effectiveness of iron supplementation remains unclear. This study aimed to determine whether aerobic training modifies the assessment of the effectiveness of iron supplementation in improving conventional iron status measures. Seventy-two iron-depleted, nonanemic Chinese women [serum ferritin (sFer) <25 μg/L and hemoglobin >110 g/L] were included in an 8-wk, partially blinded, randomized controlled trial with a 2 × 2 factorial design including iron supplements (42 mg elemental Fe/d) or placebo and aerobic training (five 25-min sessions/wk at 75-85% of maximum heart rate) or no training. Linear mixed models were used to evaluate the relation between supplement type, training, and changes in iron status over time, measured by sFer, hemoglobin, soluble transferrin receptor (sTfR), and estimated total body iron. After treatment, both the iron-supplemented trained and untrained groups showed significantly improved sFer, sTfR, and body iron values compared with either of the placebo groups. Similarly, trained participants had significantly higher aerobic fitness measures than untrained participants. Training modified the sFer response to supplementation (training by supplement interaction, = 0.07), with the iron-supplemented trained group having significantly lower sFer than the iron-supplemented untrained group at week 8 (mean ± SD: 31.8 ± 13.5 and 47.6 ± 15.7 μg/L, respectively; = 0.042), whereas there was no significant difference between the placebo trained and untrained groups (21.3 ± 12.2 and 20.3 ± 7.0 μg/L, respectively; = 1.00). Regular aerobic training reduces the apparent effectiveness of iron supplementation in improving sFer and calls into question whether conventional measures of iron status accurately reflect iron metabolism in physically active, nonanemic women. This trial was registered at clinicaltrials.gov as NCT03002090.

The Impact of Iron Supplementation on Athletic Performance in Elite-Level Female Athletes–A Systematic Review

“…Consumption of food, including supplements and medications, or beverages other than water and strenuous physical activity 2 hours before testing were restricted in 1 study (6). Subjects were excluded in 1 study for recent consumption of iron supplements, vitamin supplements, or medication that had anticoagulant properties or possibly affected dietary iron intake or absorption (23).…”

“…Five studies included subjects who were trained in specific sports, including rowing (6), volleyball (19), distance running (13), netballing (1), or aerobic training (11). Four studies identified their subjects as untrained or previously untrained (3,23,24,29). However, all subjects had to participate in a training regimen during the time of study for the study to be included in this review.…”

“…Training sessions lasted 25 minutes and were divided into 2 target heart rates of 75 and 85% of age-estimated maximums (23,24). One of these studies specified that it consisted of performing on a stationary exercise bicycle and the training regimen lasted for 8 weeks, with a maximum number of training days being 40 (23). Dellavalle and Haas (6) conducted a 6-week study where physical fitness and endurance performance were measured in rowers before and after the study using a rowing ergometer.…”

Malnutrition in Orthopaedic Sports Medicine: A Review of the Current Literature

“…20 In these cases, red blood cell morphology, mean corpuscular volume, and/or other parameters of iron depletion must also be abnormal to determine true ID. 54 Iron supplementation in those with deficiencies improves aerobic fitness measures, 61 endurance capacity, 74 energy efficiency, 74 and skeletal muscle strength. 26 other Micronutrient Deficiencies…”

Effects of morning and nocturnal soccer matches on levels of some trace elements in young trained males

“…A variety of studies with different experimental design, including aerobic, anaerobic or endurance exercise have been performed to obtain some information about the relationships between trace elements of Fe, Cu and Zn and exercise. Many studies showed that various intensity of exercise has significant effects on trace element metabolism (8,(11)(12)(13)(14). In contrast, unchanged trace elements levels after acute exercise has also been reported (15).…”