Iron and Reduced Iron Deficiency

Research synthesisModerate evidenceMixed effect size5 studies · 5 beneficial · 0 neutral · 0 harmful

Across 5 studies, all reported beneficial effects of iron on reducing iron deficiency, with effect sizes ranging from small to large (predominantly moderate to large). The most studied populations were pregnant women and clinical groups (e.g., celiac disease), with doses varying widely from 4.2 mg/day to 55 mg/day or fortification levels. All five studies showed statistically significant reductions, but the evidence certainty is low to moderate, and the overwhelming positive direction raises concerns about publication bias.

Studied populations: pregnant women and individuals with clinical conditions (e.g., celiac disease)

Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Effect sizes varied substantially across studies, and many trials used fortified foods rather than direct supplementation, which may not be directly comparable. The meta-analyses themselves rated the evidence as low-certainty due to risk of bias and imprecision.

Generated Jul 14, 2026

Doses used in studies

mg/day: 4.2–55 (median 16.95, IQR 4.25–42.3) — 2 studies
mg/100g: 0.2–112.8 (median 56.5, IQR 0.2–112.8) — 1 study

Safety in these studies

adverse effectsIncreased riskRR 1.29 (95% CI 0.83 to 2.02)
The evidence is very uncertain for adverse effects (21.6% versus 18.0%; RR 1.29, 95% CI 0.83 to 2.02; 12 trials, 2423 women; very low-certainty evidence)
from: Daily oral iron supplementation during pregnancy.
hookworm infectionIncreased riskRR 1.78, 95% CI 1.18 to 2.70; 785 participants
One study reported that fortification of rice with iron alone or with other micronutrients may slightly increase hookworm infection (RR 1.78, 95% CI 1.18 to 2.70; 785 participants; low-certainty evidence).
from: Fortification of rice with vitamins and minerals for addressing micronutrient malnutrition
severe anaemiaIncreased riskSerious adverse eventRR 0.22 (95% CI 0.01 to 3.20)
The evidence is very uncertain for ... severe anaemia (Hb < 70 g/L) in the second/third trimester (< 1% versus 3.6%; RR 0.22, 95% CI 0.01 to 3.20; 8 trials, 1398 women; very low-certainty evidence)
from: Daily oral iron supplementation during pregnancy.
congenital anomaliesNo significant differenceSerious adverse eventRR 0.88 (95% CI 0.58 to 1.33)
There may be little to no difference in ... congenital anomalies, including neural tube defects (41 versus 48 events; RR 0.88, 95% CI 0.58 to 1.33; 4 trials, 14,377 infants; low-certainty evidence)
from: Daily oral iron supplementation during pregnancy.
maternal deathNo significant differenceSerious adverse eventRR 0.57 (95% CI 0.12 to 2.69)
There is probably little to no difference in maternal death (2 versus 4 events, RR 0.57, 95% CI 0.12 to 2.69; 3 trials, 14,060 women; moderate-certainty evidence)
from: Daily oral iron supplementation during pregnancy.
neonatal deathNo significant differenceSerious adverse eventRR 0.98 (95% CI 0.77 to 1.24)
There may be little to no difference in neonatal death (1.4% versus 1.5%, RR 0.98, 95% CI 0.77 to 1.24; 4 trials, 17,243 infants; low-certainty evidence)
from: Daily oral iron supplementation during pregnancy.
Overall tolerabilityReported
No studies reported adverse effects.
from: Fortification of condiments and seasonings with iron for preventing anaemia and improving
clinical malariaReported
No trials reported clinical malaria or infection during pregnancy.
from: Daily oral iron supplementation during pregnancy.
diarrhoeaReportedRR 3.52, 95% CI 0.18 to 67.39; 1 study, 258 participants
We are uncertain about the effect of fortified rice on diarrhoea (RR 3.52, 95% CI 0.18 to 67.39; 1 study, 258 participants; very low-certainty evidence).
from: Fortification of rice with vitamins and minerals for addressing micronutrient malnutrition

5 of 5 papersPopulation:

Daily oral iron supplementation during pregnancy.
- 2024-08-15
- Meta-Analysis · n = 2,873
- The Cochrane database of systematic reviews 2024(8)
- - Julia L Finkelstein
  - Anna Cuthbert
  - Jo Weeks
  - Sudha Venkatramanan
  - Doreen Y Larvie
  - Luz Maria De-Regil
  - Maria Nieves Garcia-Casal
- PubMed: 39145520
- DOI: 10.1002/14651858.cd004736.pub6
12 Insights on
- Reduced Iron Deficiency
- High evidence
- Pregnant Women
may reduce maternal iron deficiency at term (3.6% versus 15%; RR 0.24, 95% CI 0.06 to 0.99; 1 trial, 131 women; low-certainty evidence)
Effect
Beneficial
Effect size
Large
Significant
Yes
Fortification of condiments and seasonings with iron for preventing anaemia and improving health.
- 2023-09-01
- Meta-Analysis · n = 4,459
- The Cochrane database of systematic reviews 2023(9)
- - Chowdhury Sb Jalal
  - Luz Maria De-Regil
  - Vanessa Pike
  - Prasanna Mithra
- PubMed: 37665781
- DOI: 10.1002/14651858.cd009604.pub2
4 Insights on
- Reduced Iron Deficiency
- High evidence
- Clinical
It may reduce ID (RR 0.36, 95% CI 0.19 to 0.69; 1154 participants; 4 studies; low-certainty evidence).
Effect
Beneficial
Effect size
Large
Significant
Yes
Dose
4.4–55 mg/day
Fortification of rice with vitamins and minerals for addressing micronutrient malnutrition.
- 2019-10-25
- Meta-Analysis · n = 8,245
- The Cochrane database of systematic reviews 2019(10)
- - Juan Pablo Peña-Rosas
  - Prasanna Mithra
  - Bhaskaran Unnikrishnan
  - Nithin Kumar
  - Luz Maria De-Regil
  - N Sreekumaran Nair
  - Maria N Garcia-Casal
  - Juan Antonio Solon
- PubMed: 31684687
- DOI: 10.1002/14651858.cd009902.pub2
8 Insights on
- Reduced Iron Deficiency
- High evidence
- Mixed
may reduce the risk of iron deficiency (RR 0.66, 95% CI 0.51 to 0.84; 8 studies, 1733 participants; low-certainty evidence)
Effect
Beneficial
Effect size
Small
Significant
Yes
Dose
0.2 to 112.8 mg/100 g uncooked rice
The effect of Lactiplantibacillus plantarum 299v together with a low dose of iron on iron status in healthy pregnant women: A randomized clinical trial
- 2021-04-21
- RCT
- Acta Obstetricia et Gynecologica Scandinavica 100(9)
- - U. Axling
  - G. Önning
  - Titti Martinsson Niskanen
  - N. Larsson
  - S. Hansson
  - L. Hulthén
- PubMed: 33880752
- DOI: 10.1111/aogs.14153
17 Insights on
- Reduced Iron Deficiency
- High evidence
- Pregnant Women
resulted in reduced prevalence of iron deficiency (59% vs 78%, p = 0.017) and iron deficiency anemia (7.4% vs 21%, p = 0.023) at week 35
Effect
Beneficial
Effect size
Moderate
Significant
Yes
Dose
30 µg
Ironing Out the Deficiency: Tracking Iron in Celiac Disease Before and After the Gluten-Free Diet.
- 2026-02-11
- Review
- Nutrients 18(4)
- - Patricia Dillawn
  - Sadie Nagle
  - Edwin Liu
  - Marisa Gallant Stahl
- PubMed: 41754107
- DOI: 10.3390/nu18040590
1 Insight on
- Reduced Iron Deficiency
- Moderate evidence
- Rigorous Journal
- Clinical
Celiac disease (CeD) is a gluten-induced immune-mediated enteropathy that preferentially involves the proximal duodenum. Consequently, iron deficiency is common in CeD, impacting at least 10% of newly diagnosed individuals.
Effect
Beneficial
Effect size
Moderate
Significant
Yes

Iron and Reduced Iron Deficiency

Daily oral iron supplementation during pregnancy.

Fortification of condiments and seasonings with iron for preventing anaemia and improving health.

Fortification of rice with vitamins and minerals for addressing micronutrient malnutrition.

The effect of Lactiplantibacillus plantarum 299v together with a low dose of iron on iron status in healthy pregnant women: A randomized clinical trial

Ironing Out the Deficiency: Tracking Iron in Celiac Disease Before and After the Gluten-Free Diet.