The effect of low versus high fractional iron absorption on iron absorption and utilization
Stoffel NU, et al • American Journal of Clinical Nutrition
Key Finding
Alternate-day iron absorption 40-50% higher than consecutive day (p<0.001); 200mg alternate-day yields ~2x total absorption vs 100mg consecutive-day
Key Findings
- 1Alternate-day absorption 40-50% higher (p<0.001)
- 2Hepcidin elevation on consecutive days impairs absorption
- 3200mg alternate-day = 2x absorption vs 100mg consecutive
- 4No significant difference in GI side effects
Original title: “Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women”
Plain English Summary
Cross-over study in 19 women with iron-deficiency anemia found that alternate-day iron dosing increases fractional iron absorption by 40-50% compared to consecutive-day dosing due to lower hepcidin levels. Total iron absorption from 200mg alternate-day was twice that from 100mg consecutive-day.
In-Depth Analysis
Abstract
"Alternate day dosing of oral iron supplements in anemic women may be preferable because it sharply increases FIA [fractional iron absorption]."
Methods
- •Design: Cross-over study with two 6-day cycles separated by 16 days
- •Sample: 19 women with IDA (median hemoglobin 11.5 g/dL)
- •Intervention: 100 or 200 mg ferrous sulfate on days 2, 3 (consecutive), and day 5 (alternate)
- •Measurement: Erythrocyte isotope incorporation 16 days post-administration
Key Results
Fractional Iron Absorption
- •Days 2 and 5 absorption was 40-50% higher than day 3 (P<0.001)
- •Serum hepcidin significantly elevated on day 3 vs days 2 and 5 (P<0.01)
Total Iron Absorption
- •200 mg alternate-day: approximately twice that from 100 mg consecutive-day (P<0.001)
Side Effects
- •GI side effects showed no statistically significant difference between doses (P=0.105)
Conclusions
Alternate-day administration enhances iron absorption efficiency, potentially allowing lower total doses while maintaining therapeutic benefit.
Paradigm Relevance
How this study applies to different clinical perspectives:
Standard Medical
Conventional clinical guidelines used by most doctors
Not directly relevant to this paradigm
Research Consensus
RelevantCurrent scientific understanding, often ahead of guidelines
Why it matters:
Strong evidence for hepcidin-mediated absorption dynamics; replicated in subsequent studies
Metabolic Optimization
RelevantProactive targets for optimal health, not just disease absence
Why it matters:
Practical protocol for maximizing iron supplementation efficiency—take every other day, not daily
Study Details
- Type
- Randomized Controlled Trial
- Methodology
- Cross-over study; N=19 women with IDA (median Hb 11.5 g/dL); two 6-day cycles separated by 16 days; 100 or 200 mg ferrous sulfate with stable iron isotopes
Evidence Quality
Grade B - Cross-over study with isotope measurements. Source: PMC7193469
Related Biomarkers
Calculate & Evaluate on Metabolicum
Original Source
DOI (Digital Object Identifier) is a permanent link to this publication. Unlike website URLs that can change, a DOI always resolves to the correct source.
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