Iron

Iron is an essential mineral best known for helping red blood cells to carry oxygen. Except in the case of deficiency, iron supplementation has no proven benefit; on the contrary, it can lead to side effects and increased oxidative stress.

Quick Answer

What it is

Iron is an essential mineral best known for helping red blood cells to carry oxygen. Except in the case of deficiency, iron supplementation has no proven benefit; on the contrary, it can lead to side effects and increased oxidative stress.

Key findings

  • Grade B: Anemia Risk (Metabolic Health)
  • Grade B: Ferritin (Pregnancy and Delivery Health)
  • Grade B: "Measures of Intelligence " (Focus & Attention)

Safety

No specific caution or interaction language was detected in the current summary/outcome notes.

ℹ️ Quick Facts: Iron

Quick Facts: Iron

  • Best Evidence:Grade B
  • Conditions Studied:17
  • Research Outcomes:70
  • Grade B Findings:7
  • Key Effect:Metabolic Health
Outcomes by grade:
A0
B7
C4
D4
17 conditions Β· 70 outcomes

Detailed Outcomes

Grade:
Effect:
Size:
Sort:
|
B
Anemia Risk
Small Improvement
69 studies
small↓Improves
?
Iron Deficiency Risk
48 studies
↑Worsens
?
Iron Deficiency Anemia Risk
27 studies
↑Worsens
?
Ferritin
8 studies
↑Improves
?
Hemoglobin
↑Improves
?
Serum Iron
2 studies
↑Improves
?
Total Iron Binding Capacity
2 studies
↑Improves
?
Transferrin
2 studies
↑Improves
B
Ferritin
Moderate Increase
15 studies
moderate↑Improves
?
Hemoglobin
↑Improves
?
Iron Deficiency Anemia Risk
4 studies
↑Worsens
?
Iron Deficiency Risk
4 studies
↑Worsens
?
Infant Birth Weight
↓Improves
B
"Measures of Intelligence "
Small Improvement
10 studies
small↑Improves
?
Memory
5 studies
↑Improves
?
Short-Term Memory (Simple)
4 studies
↑Improves
?
Attention
↑Improves
B
"Measures of Intelligence "
Small Improvement
10 studies
small↑Improves
?
Memory
5 studies
↑Improves
?
Short-Term Memory (Simple)
4 studies
↑Improves
?
Attention
↑Improves
B
"Measures of Intelligence "
Small Improvement
10 studies
small↑Improves
?
Memory
5 studies
↑Improves
?
Attention
↑Improves
B
Infant Birth Weight
Small Increase
small↓Improves
?
Iron Deficiency Anemia Risk
4 studies
↑Worsens
?
Iron Deficiency Risk
4 studies
↑Worsens
B
Infant Birth Weight
Small Increase
small↓Improves
?
Iron Deficiency Anemia Risk
4 studies
↑Worsens
?
Iron Deficiency Risk
4 studies
↑Worsens
C
Alertness
Small Improvement
1 study
small↑Improves
D
Aerobic Exercise Metrics
No effect
none
?
Anemia Risk
69 studies
↑Worsens
?
Iron Deficiency Risk
48 studies
↑Worsens
?
Iron Deficiency Anemia Risk
27 studies
↑Worsens
?
Hemoglobin
↑Improves
?
Ferritin
15 studies
↑Improves
?
Depression Symptoms
↓Improves
?
Fatigue Symptoms
1 study
↓Improves
?
Memory
1 study
↑Improves
?
Stress Signs and Symptoms
↓Improves
C
Anxiety Symptoms
Small Improvement
small↓Improves
?
Exercise Capacity
↑Improves
?
Depression Symptoms
↓Improves
C
6-Minute Walking Test Performance
Small Improvement
1 study
small↑Improves
?
Risk of Hospitalization for Heart Failure
9 studies
↓Improves
?
Cardiovascular Disease Mortality
↓Improves
?
Hemoglobin
↑Improves
?
Ferritin
4 studies
↑Improves
?
Left Ventricular Ejection Fraction
3 studies
↑Improves
?
All-Cause Mortality
↓Improves
?
Exercise Capacity
↑Improves
?
Quality of Life
1 study
↑Improves
C
Anemia Risk
Small Improvement
1 study
small↓Improves
?
Ferritin
1 study
↑Improves
?
Hemoglobin
↑Improves
D
Aerobic Exercise Metrics
No effect
none
?
Depression Symptoms
↓Improves
?
Heart Rate
↓Improves
?
Muscular Endurance
↑Improves
?
Oxygen Uptake
1 study
↑Improves
?
Respiratory Exchange Ratio
1 study
↑Improves
D
Aerobic Exercise Metrics
No effect
none
?
Exercise Capacity
↑Improves
D
Aerobic Exercise Metrics
No effect
none
?
Depression Symptoms
↓Improves
?
Fibromyalgia Symptoms
↓Improves
?
Muscular Endurance
↑Improves
?
Aerobic Exercise Metrics
↑Improves
?
Muscular Endurance
↑Improves

Evidence by Condition

Best grade per condition (each condition may have multiple outcomes)

BMetabolic Health
1
↓Anemia RiskImproves↑Iron Deficiency RiskWorsens↑Iron Deficiency Anemia RiskWorsens
BPregnancy and Delivery Health
1
↑FerritinImproves↑HemoglobinImproves↑Iron Deficiency Anemia RiskWorsens
BFocus & Attention
1
↑"Measures of Intelligence "Improves↑MemoryImproves↑Short-Term Memory (Simple)Improves
BMemory Improvement
1
↑"Measures of Intelligence "Improves↑MemoryImproves↑Short-Term Memory (Simple)Improves
BCognitive Improvement
1
↑"Measures of Intelligence "Improves↑MemoryImproves↑AttentionImproves
BInfant Health
1
↓Infant Birth WeightImproves↑Iron Deficiency Anemia RiskWorsens↑Iron Deficiency RiskWorsens
BLow Birth Weight
1
↓Infant Birth WeightImproves↑Iron Deficiency Anemia RiskWorsens↑Iron Deficiency RiskWorsens
CIron Deficiency Anemia
2
↑AlertnessImprovesAerobic Exercise Metrics↑Anemia RiskWorsens
CFatigue
1
↓Anxiety SymptomsImproves↑Exercise CapacityImproves↓Depression SymptomsImproves
CHeart Failure
1
↑6-Minute Walking Test PerformanceImproves↓Risk of Hospitalization for Heart FailureImproves↓Cardiovascular Disease MortalityImproves
CMenstrual Health
1
↓Anemia RiskImproves↑FerritinImproves↑HemoglobinImproves
DGeneral Athletic Performance
1
Aerobic Exercise Metrics↓Depression SymptomsImproves↓Heart RateImproves
DAerobic Exercise Performance
1
Aerobic Exercise Metrics↑Exercise CapacityImproves
DMood Improvement
1
Aerobic Exercise Metrics↓Depression SymptomsImproves

Research Citations (21)

Randomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and mood
PMID: 19474138
Clinical evaluation of iron treatment efficiency among non-anemic but iron-deficient female blood donors: a randomized controlled trial
PMID: 22272750
Evaluation of a single dose of ferric carboxymaltose in fatigued, iron-deficient women--PREFER a randomized, placebo-controlled study
PMID: 24751822
Role of iron in the reduction of anemia among women of reproductive age in low-middle income countries: insights from systematic review and meta-analysis.
PMID: 37069552
Oral iron supplementation and anaemia in children according to schedule, duration, dose and cosupplementation: a systematic review and meta-analysis of 129 randomised trials.
PMID: 36849195
Efficacy of daily versus intermittent oral iron supplementation for prevention of anaemia among pregnant women: a systematic review and meta-analysis.
PMID: 39114275
Marginal iron deficiency without anemia impairs aerobic adaptation among previously untrained women
PMID: 11916761
Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women
PMID: 12540406
Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial
PMID: 22777991
Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials
PMID: 29626044

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