Cited by 126Iron Metabolism and DisordersErythropoietin and Anemia TreatmentHemoglobinopathies and Related Disorders

The DOI matches its Crossref record; 41 of the 41 references it cites were found in a registry or an index; 3 of the 8 sources its claims cite were checked for support.

Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials

Open access

Abstract

Objective Iron supplementation in iron-deficiency anaemia is standard practice, but the benefits of iron supplementation in iron-deficient non-anaemic (IDNA) individuals remains controversial. Our objective is to identify the effects of iron therapy on fatigue and physical capacity in IDNA adults. Design Systematic review and meta-analysis of randomised controlled trials (RCTs). Setting Primary care. Participants Adults (≥18 years) who were iron deficient but non-anaemic. Interventions Oral, intramuscular or intravenous iron supplementation; all therapy doses, frequencies and durations were included. Comparators Placebo or active therapy. Results We identified RCTs in Medline, Embase, Cochrane Central Register of Controlled Trials, Cumulative Index of Nursing and Allied Health, SportDiscus and CAB Abstracts from inception to 31 October 2016. We searched the WHO’s International Clinical Trials Registry Platform for relevant ongoing trials and performed forward searches of included trials and relevant reviews in Web of Science. We assessed internal validity of included trials using the Cochrane Risk of Bias tool and the external validity using the Grading of Recommendations Assessment, Development and Evaluation methodology. From 11 580 citations, we included 18 unique trials and 2 companion papers enrolling 1170 patients. Using a Mantel-Haenszel random-effects model, iron supplementation was associated with reduced self-reported fatigue (standardised mean difference (SMD) −0.38; 95% CI −0.52 to −0.23; I 2 0%; 4 trials; 714 participants) but was not associated with differences in objective measures of physical capacity, including maximal oxygen consumption (SMD 0.11; 95% CI −0.15 to 0.37; I 2 0%; 9 trials; 235 participants) and timed methods of exercise testing. Iron supplementation significantly increased serum haemoglobin concentration (MD 4.01 g/L; 95% CI 1.22 to 6.81; I 2 48%; 12 trials; 298 participants) and serum ferritin (MD 9.23 µmol/L; 95% CI 6.48 to 11.97; I 2 58%; 14 trials; 616 participants). Conclusion In IDNA adults, iron supplementation is associated with reduced subjective measures of fatigue but not with objective improvements in physical capacity. Given the global prevalence of both iron deficiency and fatigue, patients and practitioners could consider consumption of iron-rich foods or iron supplementation to improve symptoms of fatigue in the absence of documented anaemia. PROSPERO registration number CRD42014007085 .

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

In non-anaemic iron-deficient adults, iron supplementation reduced self-reported fatigue but did not improve objective physical capacity. It increased haemoglobin and ferritin, with evidence graded moderate for fatigue and low for physical capacity.

Key findings

  • From 11,580 citations, the review included 18 unique trials and 2 companion papers enrolling 1170 patients. Iron supplementation reduced self-reported fatigue (SMD −0.38; 95% CI −0.52 to −0.23; I² 0%; 4 trials; 714 participants).
  • Iron did not significantly improve objective physical capacity: VO₂ max (SMD 0.11; 95% CI −0.15 to 0.37; I² 0%; 9 trials; 235 participants), 15 km time trial (SMD −0.09; 95% CI −0.53 to 0.35; I² 0%; 2 trials; 79 participants), or time to exhaustion (SMD 0.25; 95% CI −0.22 to 0.73; I² 0%; 4 trials; 69 participants).
  • Iron significantly increased serum haemoglobin (MD 4.01 g/L; 95% CI 1.22 to 6.81; I² 48%; 12 trials; 298 participants) and serum ferritin (MD 9.23 µmol/L; 95% CI 6.48 to 11.97; I² 58%; 14 trials; 616 participants). Adverse events were sparsely reported; adherence did not differ (RR 1.0; 95% CI 0.99 to 1.01; I² 0%; 12 trials; 958 participants).

Methods

  • Systematic review and meta-analysis of randomised controlled trials in adults (≥18 years) who were iron deficient but non-anaemic, comparing oral, intramuscular, or intravenous iron with placebo or active therapy; outcomes assessed at least 28 days after starting therapy.
  • Searched Medline, Embase, Cochrane Central Register of Controlled Trials, Cumulative Index of Nursing and Allied Health, SportDiscus, and CAB Abstracts from inception to 31 October 2016, plus trial registries and forward searches.
  • Used Mantel-Haenszel random-effects meta-analysis, mean difference or standardised mean difference for continuous outcomes, I² for heterogeneity, Cochrane Risk of Bias tool, and GRADE; PROSPERO registration CRD42014007085.

Limitations

  • Stated by the paper: search was limited to English studies; dietary iron fortification studies were excluded; masking oral iron was difficult due to predictable gastrointestinal side effects and stool colour changes; healthy women comprised the population in 15 of 18 trials; follow-up was relatively short (mean 57 days; range 28–112 days); adverse events were sparsely reported; most trials were at unclear risk of bias; publication bias could not be assessed for fatigue because of the low number of included trials.
  • Evident from the text: subgroup analyses for biological sex, athletic status, and risk of bias were often unevaluable because contributing trials enrolled women of uncharacterised athletic status and were of unclear risk of bias; the fatigue outcome was subjective and potentially vulnerable to imperfect blinding.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1136/bmjopen-2017-019240

Cites

41 of 41 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

3 of 8 cited sources checked · 1 supported · 0 flagged · accuracy not yet measured

Show all 26 claims

  • It may state two separate claims as one. 16
  • Probably not a substantial claim. 16
25 of 25
  • The paper relies on this without support.

    It is unclear whether iron supplementation affects fatigue and physical capacity in iron-deficient but non-anaemic individuals.

    “While iron replacement can normalise haemoglobin concentration, restore work capacity and improve fatigue in iron-deficiency anaemia, it is unclear if supplementation affects fatigue and physical capacity in iron-deficient but non-anaemic (IDNA) individuals.”
  • The paper relies on this without support.

    The use of iron supplements is common in the general population and routinely recommended to high performance athletes to enhance performance.

    “In the absence of compelling efficacy data on well-being or muscle function, the use of iron supplements is common in the general population and are routinely recommended to high performance athletes to enhance performance.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Oral-iron trial described as using intramuscular iron

    Major

    The adverse-events section describes trial 29 as using intramuscular iron, but Table 1 identifies Flink et al (trial 29) as using oral iron.

  • Not all trials had placebo controls

    Minor

    The statement that all trials were placebo controlled conflicts with Table 1, which lists zinc gluconate as the control for Donangelo et al.

2 of 2

Citations

Cites

Flagged first, then by citations

Show all 41 references

Research works printed but not linked: 1

  1. Hurrie D , Graham J , Rimmer E , et al . Efficacy of iron replacement therapy on fatigue and work capacity in non-anemic adults with iron depletion: a systematic review of randomized controlled trials. PROSPERO International prospective register of systematic reviews, 2014.

Cited by

Sorted by citations

Items 101–126 of 126

Metadata

Authors
Houston, B. L., Hurrie, D., Graham, J., Perija, B., Rimmer, E., Rabbani, R., Bernstein, C. N., Turgeon, A. F., Fergusson, D. A., Houston, D. S., Abou-Setta, A. M., & Zarychanski, R.
Affiliations
  • CancerCare Manitoba (CA)
  • University of Manitoba (CA)
  • Winnipeg Regional Health Authority (CA)
  • Université Laval (CA)
  • University of Ottawa (CA)
Corresponding author
Zarychanski, Ryan
Venue
BMJ Open
Publisher
BMJ
Published
2018-04
Volume
8
Issue
4
Pages
e019240
ISSN
2044-6055 (ISSN-L)
OpenAlex
W2796265630
Cited by
126
References
41
Citations by year
2026: 12 · 2025: 16 · 2024: 20 · 2023: 13 · 2022: 16 · 2021: 17 · 2020: 15 · 2019: 13 · 2018: 4
FWCI
2.89
Type
journal article
Language
en
Open access
Licence
cc-by-nc
Locations
  • BMJ Open (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (submittedVersion, other-oa)
  • PubMed Central (submittedVersion, cc-by-nc)
Topics
  • Health Sciences › Medicine › Hematology › Iron Metabolism and Disorders
  • Health Sciences › Medicine › Hematology › Erythropoietin and Anemia Treatment
  • Health Sciences › Medicine › Genetics (clinical) › Hemoglobinopathies and Related Disorders
Keywords
iron supplementation, iron deficiency anemia, fatigue, physical capacity, VO2max, exercise testing, serum ferritin, oral iron, intramuscular iron, intravenous iron, adverse effects, iron deficiency in pregnancy, iron deficiency in children
MeSH terms
Iron Deficiencies, Adult, Fatigue, Female, Ferritins, Humans, Iron, Male, Randomized Controlled Trials as Topic

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