Studies

Explore research connecting ingredients and health goals.

25 ingredient–goal connections

GoalReported findings
SupportiveMixedNo effectAdverseUnclassified

EnergyandIron

74published studies

Supportive

The available evidence supports iron replacement as a way to reduce fatigue associated with iron deficiency. Oral supplementation improves iron status and can improve fatigue and exercise performance, particularly in research involving menstruating women. Some people with low iron stores but normal hemoglobin also benefit, although results are less consistent than a simple energy-boost claim would imply.

Fatigue has multiple contributors. Controlled research in iron-deficient blood donors has found improved blood markers without less fatigue, and some clinical populations show little relationship between fatigue and iron status. Replenishing iron stores therefore does not guarantee a noticeable increase in energy.

Many favorable studies concern intravenous treatment for anemia during pregnancy, after bleeding or alongside chronic disease. These medical settings do not establish the same benefit from a routine oral supplement in someone with adequate iron. Treatment-related effects also matter: oral iron can cause digestive symptoms, while certain intravenous formulations can lower phosphate and contribute to weakness or fatigue. Overall, the benefit is best understood as correction of deficiency, rather than general stimulation.

74 linked studies · 29 sampled for detail · Sep 27, 2026

Study types

  • Randomized trial26
  • Narrative review13
  • Cross-sectional study9
  • Cohort study6
  • Meta-analysis6
  • Single-arm trial4
  • Non-randomized trial3
  • Other2
  • Case series1
  • Methods validation study1
  • Observational study1
  • Protocol1
  • Systematic review1

Published by year

  • 7Earlier
  • 12010
  • 12011
  • 42012
  • 22013
  • 22014
  • 32015
  • 12016
  • 52017
  • 22018
  • 52019
  • 52020
  • 42021
  • 92022
  • 22023
  • 82024
  • 62025
  • 72026

Findings over time

Numbers above bars show study counts. Earlier groups years before 2010.

20267 studies

  • Supportive3
  • Mixed2
  • No effect2
  • Adverse0
  • Unclassified0

Population over time

Reported participants by publication year. Select a year to see the total and reporting coverage.

— Participant count not reported. Earlier groups years before 2010.

20261,047 reported participants

Counts reported by 5 of 7 studies. 2 without a reported count.

Totals sum reported counts across studies and reviews; participants may overlap between sources.

Explore this goal

Showing 5 top-ranked studies for Iron and Energy.

Top studies

Iron · EnergyHighest ranked first
  1. Large-dose intravenous ferric carboxymaltose injection for iron deficiency anemia in heavy uterine bleeding: a randomized, controlled trial.
    2010Randomized trial477 participants

    Transfusion

    Finding IV ferric carboxymaltose produced larger hemoglobin responses and more anemia correction than oral ferrous sulfate in this population.

    SupportiveView source for Large-dose intravenous ferric carboxymaltose injection for iron deficiency anemia in heavy uterine bleeding: a randomized, controlled trial. (opens in a new tab)
  2. The Effect of Parenteral or Oral Iron Supplementation on Fatigue, Sleep, Quality of Life and Restless Legs Syndrome in Iron-Deficient Blood Donors: A Secondary Analysis of the IronWoMan RCT.
    2021Randomized trial176 participants

    Nutrients

    Finding Iron supplementation significantly improved the severity of restless legs, fatigue, and sleep-quality symptoms (p < 0.001).

    SupportiveView source for The Effect of Parenteral or Oral Iron Supplementation on Fatigue, Sleep, Quality of Life and Restless Legs Syndrome in Iron-Deficient Blood Donors: A Secondary Analysis of the IronWoMan RCT. (opens in a new tab)
  3. Ferric carboxymaltose vs. oral iron in the treatment of pregnant women with iron deficiency anemia: an international, open-label, randomized controlled trial (FER-ASAP).
    2018Randomized trial252 participants

    Journal of perinatal medicine

    Finding Hemoglobin improved at comparable rates, but more women achieved the stated anemia-correction threshold with FCM and did so in a shorter median time.

    SupportiveView source for Ferric carboxymaltose vs. oral iron in the treatment of pregnant women with iron deficiency anemia: an international, open-label, randomized controlled trial (FER-ASAP). (opens in a new tab)
  4. Effect of iron therapy on fatigue symptoms in non-anaemic iron deficient women of reproductive age- A Randomized Controlled Trial.
    2026Randomized trial164 participants

    JPMA. The Journal of the Pakistan Medical Association

    Finding Iron treatment significantly decreased fatigue scores and increased ferritin and hemoglobin after intervention.

    SupportiveView source for Effect of iron therapy on fatigue symptoms in non-anaemic iron deficient women of reproductive age- A Randomized Controlled Trial. (opens in a new tab)
  5. Intravenous iron isomaltoside treatment of women suffering from severe fatigue after postpartum hemorrhage.
    2019Randomized trial85 participants

    The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians

    Finding Among 85 women with high baseline fatigue, physical fatigue decreased significantly by an aggregate -2.3 points in favor of iron isomaltoside.

    SupportiveView source for Intravenous iron isomaltoside treatment of women suffering from severe fatigue after postpartum hemorrhage. (opens in a new tab)

Counts reflect published studies in our database, not the strength of a benefit. A study may appear in more than one connection.