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

Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training

This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90-min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O2peak) exercise using indirect calorimetry, and 6-6-[2H2]-glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE (p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased (p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST (p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole-body and skeletal muscle fat metabolism.

The relationship between hemoglobin and [Formula: see text]: A systematic review and meta-analysis

OBJECTIVE

There is widespread agreement about the key role of hemoglobin for oxygen transport. Both observational and interventional studies have examined the relationship between hemoglobin levels and maximal oxygen uptake ([Formula: see text]) in humans. However, there exists considerable variability in the scientific literature regarding the potential relationship between hemoglobin and [Formula: see text]. Thus, we aimed to provide a comprehensive analysis of the diverse literature and examine the relationship between hemoglobin levels (hemoglobin concentration and mass) and [Formula: see text] (absolute and relative [Formula: see text]) among both observational and interventional studies.

METHODS

A systematic search was performed on December 6th, 2021. The study procedures and reporting of findings followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Article selection and data abstraction were performed in duplicate by two independent reviewers. Primary outcomes were hemoglobin levels and [Formula: see text] values (absolute and relative). For observational studies, meta-regression models were performed to examine the relationship between hemoglobin levels and [Formula: see text] values. For interventional studies, meta-analysis models were performed to determine the change in [Formula: see text] values (standard paired difference) associated with interventions designed to modify hemoglobin levels or [Formula: see text]. Meta-regression models were then performed to determine the relationship between a change in hemoglobin levels and the change in [Formula: see text] values.

RESULTS

Data from 384 studies (226 observational studies and 158 interventional studies) were examined. For observational data, there was a positive association between absolute [Formula: see text] and hemoglobin levels (hemoglobin concentration, hemoglobin mass, and hematocrit (P<0.001 for all)). Prespecified subgroup analyses demonstrated no apparent sex-related differences among these relationships. For interventional data, there was a positive association between the change of absolute [Formula: see text] (standard paired difference) and the change in hemoglobin levels (hemoglobin concentration (P<0.0001) and hemoglobin mass (P = 0.006)).

CONCLUSION

These findings suggest that [Formula: see text] values are closely associated with hemoglobin levels among both observational and interventional studies. Although our findings suggest a lack of sex differences in these relationships, there were limited studies incorporating females or stratifying results by biological sex.

A systematic nutrition intervention for low iron status in collegiate distance runners

Background: Iron is a trace mineral that plays a significant role in oxygen transport and energy production during exercise. In deficiency, iron can have a significant negative impact on sports performance. Due to its relative simplicity, supplementation is a common treatment to combat deficiency. However, there is a paucity of analyses combining supplementation with dietary education as a method of treatment. Objective: To assess the effectiveness of a systematic iron intervention combining nutrition education and supplementation stages to combat low ferritin levels in collegiate runners. Methods: Twenty four distance runners (13 women; 11 men; 19.5 ± 0.8 years of age) were measured for serum ferritin, daily iron, calcium and vitamin C intake at the start of the fall semester and again after 100 days of supplementation. A dependent groups t-test was applied to delineate changes in Ferritin levels and iron, vitamin C and calcium intake. Alpha levels were maintained a priori at p < 0.05. Results: Ferritin levels averaged 40.0 ± 22.6 ng/mL in Fall and 33.7 ± 14.7 ng/mL in Spring. There were no statistical differences in ferritin levels from Fall to Spring (p = 0.074). Weekly Iron intake (# of foods) significantly increased from Fall (110.8 ± 43.1) to Spring (123.3 ± 43.9), (p = 0.028). There were no significant changes in Vitamin C or Calcium intake between time points (p = 0.441), (p = 0.901). Conclusion: We found no significant differences in serum ferritin measures but dietary intake of iron increased as a result of the intervention.

Synbiotic Supplementation Improves Response to Iron Supplementation in Female Athletes during Training

OBJECTIVE

Iron deficiency (ID) affects ∼30% of female athletes, and its consequences are highly relevant to athletic performance. Poor iron (Fe) uptake remains a major factor in the development of ID. While studies suggest that consumption of either prebiotics or probiotics may improve Fe uptake, consumption of synbiotics has not been well-studied. The main objective of this study was to determine the effects of synbiotic supplementation on the Fe status of female athletes during Fe repletion.

METHODS

The Fe status of 32 female athletes was screened early in the season. Twenty eligible athletes (hemoglobin:12.3 ± 0.9g/dL; serum ferritin, sFer:18.1 ± 9.2 µg/L) were randomized to receive either a daily synbiotic supplement (5 g prebiotic fiber + 8 billion colony forming units, CFU probiotic B. lactis) or placebo, along with Fe supplementation (140 mg ferrous sulfate, FeSO₄/d) for 8 weeks using a double-blind design. Fe status was assessed again at mid-point and after the trial.

RESULTS

Nineteen athletes (n = 9 supplement, 10 placebo) completed the trial and there were no differences in compliance or GI symptoms reported between groups. After controlling for baseline Fe status, regression analyses revealed improvements in log sFer in the supplement group after both 4 and 8 weeks (p = 0.01 and p = 0.05, respectively), compared to placebo.

CONCLUSIONS

Synbiotic supplementation along with FeSO₄ improved athletes' Fe status over 8 weeks. This data is essential to advancing our understanding of how dietary and supplemental Fe uptake in active women can be enhanced by synbiotic supplementation, as well as by foods containing pre- and probiotics.

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

CONTEXT

Malnutrition is well-studied in various aspects of the orthopaedic literature, most commonly in relation to arthroplasty, spine surgery, and trauma. However, the management of nutritional deficiencies is commonly overlooked among orthopaedic sports medicine providers. The purpose of this article is to analyze the available sports medicine literature to review the associations between malnutrition and the management of orthopaedic sports medicine patients from a treatment and performance standpoint.

EVIDENCE ACQUISITION

PubMed was searched for relevant articles published from 1979 to 2019.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 4.

RESULTS

Few studies exist on the implications of macronutrient deficiencies specific to orthopaedic sports medicine procedures. Interestingly, micronutrient disorders-namely, hypovitaminosis D and iron deficiency-have been well studied and may lead to worse postoperative outcomes, injury rates, and athletic performance. Nutritional supplementation to correct such deficiencies has been shown to mitigate these effects, though further study is required.

CONCLUSION

Nutritional deficiencies are highly prevalent in orthopaedic sports medicine patients, and practitioners should be aware of their potential effects on treatment and performance outcomes. Management of such deficiencies and their effect on surgical patients remain an area of potential future research. Future studies are warranted in order to explore the potential therapeutic role of nutritional supplementation to prevent complications after common orthopaedic sports medicine procedures, improve athletic performance, and reduce injury rates.

Menstrual blood losses and body mass index are associated with serum ferritin concentrations among female varsity athletes

Preventing and treating iron deficiency are important components in the nutritional care of female varsity athletes, as these interventions may improve aerobic endurance and athletic performance. We examined the factors associated with ferritin concentration in 30 female varsity athletes (18-30 years) at the University of British Columbia in Vancouver, Canada. Biochemical indicators of iron and inflammation status, dietary intake, supplementation practices, weight, height, and menstrual blood losses were assessed. Iron deficiency prevalence was 20% (n = 6/30; inflammation-adjusted ferritin <15 μg/L). Multiple linear regression was used to assess the associations of a number of independent explanatory variables with log-transformed serum ferritin (μg/L) as the continuous outcome variable. A 1-unit increase in body mass index (BMI; kg/m²) was associated with 22% (95% CI: 9%-37%) higher mean ferritin concentrations, and a 1-point increase in menstrual loss score was associated with 1% (95% CI: 1%-2%) lower ferritin concentrations. Hemoglobin and hepcidin concentrations, inflammation biomarkers, consumption of iron supplements in any form or dose for ≥3 days/week, and age were not significantly associated with ferritin concentrations in the final adjusted model. Novelty Estimated monthly menstrual losses and BMI were associated with serum ferritin concentrations in female athletes in our study. These are easy-to-measure, noninvasive measurements that should be considered in the assessment of risk of iron deficiency in female athletes.

Reduction of hemoglobin, not iron, inhibited maturation of red blood cells in male rats exposed to high intensity endurance exercises

The existence of sports anemia, induced by strenuous or long-term exercise and characterized by decreases of red blood cells (RBCs), hemoglobin and iron content, remains to be doubtful. To observe the effects of endurance exercise on RBCs and explain the underlying reason, we designed this study by observing RBCs parameters and iron metabolism in 8-weeks training rats and effects of iron supplement or protein supplement on RBCs. Results showed that erythrocyte counts, hematocrit, mean corpuscular volume and hemoglobin content decreased while RBC distribution width increased in exercised rats at later stage during 8 weeks training. But the contents of serum iron and ferritin decreased only at 1-week and 2-week and returned to normal at 4-week and 8-week. Same as iron content, apparent iron absorption rate was declined at early stage but restored to normal level at 8-week, as well as serum adrenaline, cortisol and insulin levels. Instead, the contents of total protein and albumin in serum were decreased at later stage during 8-weeks training. Furthermore, we observed that protein supplement ameliorated RBCs parameters in rats exposed to 8 weeks swimming exercise, but iron supplement had no effects on RBCs, though it obviously increased iron content of serum and the liver. Based on these results, we drew a conclusion that transient changes of iron metabolism, which may be induced by stress hormone changes, was not the reason for RBCs decrease in endurance exercises but hemoglobin reduction, induced by defects in protein supplement, impeded development of RBCs.

Iron, Zinc, and Physical Performance

Iron and zinc are nutritionally essential trace elements that function through incorporation into proteins and enzymes; many of these proteins and enzymes affect physical performance. Poor iron status (iron deficiency and iron deficiency anemia) is prevalent in both developed and developing nations. Zinc deficiency has been reported in clinical and population studies, although the incidence is difficult to quantify due to the lack of a reliable zinc status indicator. The objective of this manuscript is to review the relationship between iron and zinc status and physical performance. In sum, numerous reports indicate diminished physical performance in individuals with poor iron and/or zinc status, whereas, in individuals with adequate status, evidence supporting a beneficial role of iron or zinc at levels beyond the recommended dietary allowance for optimizing physical performance is lacking.

Increasing Iron Status through Dietary Supplementation in Iron-Depleted, Sedentary Women Increases Endurance Performance at Both Near-Maximal and Submaximal Exercise Intensities

BACKGROUND

Iron deficiency persists as the most common micronutrient deficiency globally, despite having known detrimental effects on physical performance. Although iron supplementation and aerobic exercise have been examined individually and are known to improve physical performance, the impact of simultaneous iron supplementation and aerobic training remains unclear.

OBJECTIVE

The aim of this study was to examine the individual and combined effects of iron supplementation and aerobic training on improving maximal and submaximal physical performance in iron-depleted, nonanemic (IDNA) women. We hypothesized that women receiving iron would improve their endurance performance but not their estimated maximal oxygen consumption (eVO2max).

METHODS

Seventy-three sedentary, previously untrained IDNA (serum ferritin <25 µg/L and hemoglobin >110 g/L) women aged 18-26 y with a body mass index (kg/m2) of 17-25 participated in a double-blind, 8-wk, randomized controlled trial with a 2 × 2 factorial design including iron supplementation (42 mg elemental Fe/d) or placebo and aerobic exercise training (5 d/wk for 25 min at 75-85% of age-predicted maximum heart rate) or no training. Linear models were used to examine relations between training, supplement, and changes in the primary outcomes of observed maximal oxygen consumption (VO2peak) and eVO2max and ventilatory threshold (absolute oxygen consumption and percentage of maximum). Re-evaluation of a published meta-analysis was used to compare effects of iron supplementation on maximal oxygen consumption (VO2max) and VO2peak.

RESULTS

There were significant training-by-supplement interactions for VO2peak, volume of oxygen consumption at the ventilatory threshold, and the percentage of eVO2max where the threshold occurred, with the iron-untrained group performing better than the placebo-untrained group. There was no beneficial effect of iron supplementation for VO2max (mean difference: 0.53; 95% CI: -0.75, 1.81; P = 0.42), but a significant benefit was observed for VO2peak (mean difference: 1.87; 95% CI: 0.15, 3.60; P = 0.03).

CONCLUSIONS

Iron supplementation increases endurance performance at submaximal and maximal (VO2peak) exercise intensities in IDNA women. However, increasing iron status does not increase eVO2max. This trial was registered at clinicaltrials.gov as NCT03002090.