Trial reportMedicine and science in sports and exercise2019
Single versus Split Dose of Iron Optimizes Hemoglobin Mass Gains at 2106 m Altitude.
Trial report in Medicine and science in sports and exercise, 2019. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 18 papers, 1 of them a synthesis that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
18 citing papers in PubMed, 1 synthesis or guideline pooled it, 27 citations in OpenAlex.
- Comparative efficacy of different dietary interventions for cardiopulmonary fitness at high altitude: a systematic review and network meta-analysis.Frontiers in nutrition · 2025Pooled it
- Effects of altitude and recombinant human erythropoietin on iron metabolism: a randomized controlled trial.American journal of physiology. Regulatory, integrative and comparative physiology · 2021Trial
- Iron Deficiency in Vegetarian Athletes: A Narrative Review.Current nutrition reports · 2026Review
- Nutrition, hydration and supplementation considerations for mountaineers in high-altitude conditions: a narrative review.Frontiers in sports and active living · 2024Review
- The IRONy in Athletic Performance.Nutrients · 2023Review
- Iron Status and Physical Performance in Athletes.Life (Basel, Switzerland) · 2023Review
- Diet, Supplementation and Nutritional Habits of Climbers in High Mountain Conditions.Nutrients · 2023Article
- Article
- Dietary Iron and the Elite Dancer.Nutrients · 2022Review
- Anemia in Sports: A Narrative Review.Life (Basel, Switzerland) · 2021Review
- Induction of erythroferrone in healthy humans by micro-dose recombinant erythropoietin or high-altitude exposure.Haematologica · 2021Article
- Preparing for the Nordic Skiing Events at the Beijing Olympics in 2022: Evidence-Based Recommendations and Unanswered Questions.Journal of science in sport and exercise · 2021Article
- Key Nutritional Considerations for Youth Winter Sports Athletes to Optimize Growth, Maturation and Sporting Development.Frontiers in sports and active living · 2021Review
- Refining Treatment Strategies for Iron Deficient Athletes.Sports medicine (Auckland, N.Z.) · 2020Review
- Dietary Adjustments to Altitude Training in Elite Endurance Athletes; Impact of a Randomized Clinical Trial With Antioxidant-Rich Foods.Frontiers in sports and active living · 2020Article
- Nutrition and Altitude: Strategies to Enhance Adaptation, Improve Performance and Maintain Health: A Narrative Review.Sports medicine (Auckland, N.Z.) · 2019Review
- Contemporary Periodization of Altitude Training for Elite Endurance Athletes: A Narrative Review.Sports medicine (Auckland, N.Z.) · 2019Review
- Iron considerations for the athlete: a narrative review.European journal of applied physiology · 2019Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
6 authors at 5 institutions in 3 countries.
Funding
Abstract
purposeTo determine if a single versus a split equivalent daily dose of elemental iron was superior for hemoglobin mass (Hbmass) gains at altitude while minimizing gastrointestinal (GI) discomfort.
methodsTwenty-four elite runners attended a 3.1 ± 0.3 wk training camp (Flagstaff, AZ; 2106 m). A two-group design, randomized and stratified to baseline Hbmass, sex, and ferritin (>30 μ·L), was implemented daily as: 1) single dose of 1 × 200 mg (PM only, SINGLE) versus 2) split dose of 2 × 100 mg (AM and PM; SPLIT) elemental iron (ferrous fumarate). The Hbmass and venipuncture assessments were completed upon arrival and departure (±2 d) from camp for ferritin, hepcidin, and erythroferrone (ERFE) concentrations. Validated food frequency, GI distress, menstrual blood loss (MBL) and training questionnaires were implemented throughout. Univariate analysis was used to compare Hbmass, with baseline ferritin, dietary iron intake, MBL, and training volume used as covariates.
resultsBoth conditions increased Hbmass from baseline (P < 0.05), with SINGLE (867.3 ± 47.9 g) significantly higher than SPLIT (828.9 ± 48.9 g) (P = 0.048). The GI scores were worse in SINGLE for weeks 1 and 2 combined (SINGLE, 18.0 ± 6.7 points; SPLIT, 11.3 ± 6.9 points; P = 0.025); however, GI scores improved by week 3, resulting in no between-group differences (P = 0.335). Hepcidin significantly decreased over time (P = 0.043) in SINGLE, with a nonsignificant decrease evident in SPLIT (~22%). ERFE significantly decreased in both groups (~28.5%; P < 0.05). No between-group differences existed for ERFE, hepcidin, food frequency, MBL, or daily training outcomes (P > 0.05).
conclusionsA single nightly 200-mg dose of elemental iron was superior to a split dose for optimizing Hbmass changes at altitude in runners over an approximately 3-wk training camp.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.