Iron DeficiencyFeSc2NCT06942208
Improving Iron Levels in Female Endurance, Intermittent, and Power/Strength Athletes Aged 16-35
A study testing Low-dose iron (ferrous sulfate), Yeast-bound iron (ferrous sulfate) and High-dose iron (ferrous sulfate) in people with Iron Deficiency, run by University of Calgary at 1 site in Canada.
Trial summary
The goal of this clinical trial is to learn if different types and doses of oral iron supplements can improve iron levels, athletic performance, and gut health in young female athletes with low iron stores. Read more about this study
- Who is it for?
- Ages 16 to 35 years, women onlyHealthy volunteers can take part
- Conditions the study is for
- Iron Deficiency
- What is being tested?
- Low-dose iron (ferrous sulfate), Yeast-bound iron (ferrous sulfate) and High-dose iron (ferrous sulfate)
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 36 participants
- Where
- 1 siteCanada
- Study dates
- 26 Mar 2026to Sep 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 16 to 35 years
- Women only
- Healthy volunteers accepted
- Child, Adult
Who may be able to join
- Biologically female athlete
- Age 16-35
- At least one year past the age of menarche
- Complete and pass the Get Active Questionnaire (GAQ)
- Suboptimal ferritin levels (≤50 mcg/L)
- Provide informed consent to participate in study
Show all 12Show fewer
- Activity level based on Participant Classification Framework (McKay et al., 2022)
- Tier 3: Highly Trained / National Level
- Tier 4: Elite / International Level
- Energy availability >30 kcal/kg LBM
- Have access to a smartphone, tablet, or computer
- Able to swallow a capsule sized 25mm length and 8mm width (i.e. large dose omega 3 pill)
Who cannot join
- Non-English speaking
- Anemic (hemoglobin <120g/L)
- Regular prebiotic (fiber) or probiotic use within 4 weeks of study enrollment
- Current laxative use
- Are a smoker or use tobacco products
- Consume >21 units of alcohol per week
Show all 53Show fewer
- Have donated blood in the previous 3 months
- Have a BMI <16 but >30kg/m2
- Are dieting for weight loss or are following a low carbohydrate diet
- Have participated in another clinical trial within the 30 days preceding study enrollment.
- Known allergy of hypersensitivity to any ingredient, including non-medicinal ingredients, such as iron, yeast, cellulose, or maltodextrin
- Are taking medications known to affect cardiovascular or metabolic responses to exercise such as beta-blockers, anti-coagulants etc. as assessed by the Principal Investigator
- Known history of thalassemia or thalassemia trait
- Known inherited bleeding disorder
- Major surgery in the past 3 months
- Chronic use of Salicylates, aspirin, corticosteroids, or nonsteroidal anti-inflammatory drugs
- Have any of the following conditions: renal or gastrointestinal disorders, autoimmune disease, metabolic disease, heart disease, vascular disease, rheumatoid arthritis, diabetes, poor lung function, uncontrolled blood pressure, dizziness, thyroid problems, or any other health conditions that are being treated and deemed to be able to significantly interfere with study intervention and assessment in the opinion of the Principal Investigator and Qualified Investigator
- Have current musculoskeletal injuries that limit exercise capacity
- Self-identifying with any kidney or gastrointestinal issues, metabolic disorders, cardiac conditions, vascular illnesses, rheumatoid arthritis, diabetes, compromised lung function, unregulated blood pressure, episodes of dizziness, thyroid complications, or any other health conditions under treatment that might potentially interfere with the study results
- Orthopaedic issues that limit exercise ability
- Currently/last 3 months taking prescription medications that are known to affect iron absorption (i.e. Antacids/PPIs (e.g., omeprazole), H2 Blockers (e.g., ranitidine), Tetracycline Antibiotics (e.g., doxycycline), Quinolone Antibiotics (e.g., ciprofloxacin), Cholestyramine, Colchicine, Methyldopa.)
- Currently taking levodopa or levothyroxine
- Currently/last 3 months taking iron containing supplements
- Are pregnant or lactating or planning to become pregnant for the duration of the study. All participants must agree to use a medically approved method of birth control for the duration of the study. All hormonal birth control must have been in use for a minimum of three months. Acceptable methods of birth control include:
- Abstinence or agrees to use contraception if planning to become sexually active
- Hormonal contraceptives including oral contraceptives, hormone birth control patch
- Vaginal contraceptive ring, injectable contraceptives, or hormone implant
- Barrier methods (e.g. condoms with spermicide, diaphragms with spermicide)
- Intrauterine devices
- Non-heterosexual lifestyle or agrees to use contraception if planning on changing to heterosexual partner(s)
- Vasectomy of partner at least 6 months prior to screening
- Additional exclusion criteria based on use of SIMBA capsules. Following is a summary of SIMBA capsules specific exclusion criteria:
- Currently pregnant, planning to become pregnant, or breastfeeding
- Prior gastrointestinal disease, surgery, or radiation treatment which, in the Investigator's opinion, would lead to intestinal structuring, narrowing, or obstruction with a risk of capsule non-excretion, including, e.g. achalasia, eosinophilic esophagitis, any IBD, or previous esophageal, gastric, small intestinal, or colonic surgery. Appendectomy or cholecystectomy more than 3 months before the screening visit is acceptable.
- History of known structural gastrointestinal abnormalities such as structures or fistulas leading to mechanical obstruction
- Have any gastrointestinal inflammatory diseases, including ulcerative colitis, Crohn's disease, microscopic colitis.
- Use of any medication in the week prior to the screening study visit, unless part of regular treatment, that could substantially alter gastrointestinal motor function (e.g. opioids, prokinetics, anticholinergics, GLP-1 analogues); laxative use is allowed if it is kept unchanged in the week prior to the study visit. Proton pump inhibitors (PPIs) are allowed provided a wash-out period of 48 hours is respected before swallowing the SIMBA capsules and PPI treatment is resumed only 4 hours thereafter.
- Prokinetic (stimulate muscle contractions, Metoclopramide, Domperidone, Prucalopride, etc.) use. If you are not using prokinetics to treat SIBO, then you may be eligible after a 2-week washout period, and willing to not use prokinetics for the study duration.
- Unable to stop using laxatives or prokinetic medications for 4 days before the study procedure (breath test). Laxatives can be resumed after the test is conducted.
- Have used antibiotics (except for topical use) in the previous 12 weeks. You may be eligible to participate once a 12-week washout is completed
- Regular use of probiotics, prebiotics, or synbiotics (including food and drinks containing added probiotics and/or probiotic yogurts with live, active cultures)
- Have digestive problems that slow or stop food from moving properly, like a slow stomach, blocked intestines, or stiffened tissues
- Suffer from celiac disease (treated or untreated)
- Organic motility disorder, including gastroparesis, intestinal pseudo-obstruction, systemic sclerosis, Ogilvie's syndrome
- History of oropharyngeal dysphagia, or other swallowing disorder with a risk of capsule aspiration
- Have had a cancer diagnosis or treatment within the past year (non-melanoma skin cancers are acceptable)
- Have trouble swallowing, which could cause a risk of choking on a capsule
- Participants scheduled for an MRI at any time during the study. You may be eligible to participate once your MRI procedure is completed.
- Have constant constipation (IBS-C) defined as a history of less than 3 bowel movements per week
- Any prior fecal microbiota transplantation
- Drug use
- Suffer from alcohol or drug abuse
- Females of childbearing potential will be asked about their likelihood of being pregnant, based on factors such as recent sexual activity or use of contraception. Their self-reported confirmation of non-pregnancy will be accepted unless they express uncertainty. In cases of doubt, a urine beta-HCG pregnancy test will be required for confirmation. If you become pregnant during the course of the study, you should stop taking the supplement immediately and inform the investigators. If you are using a supplement that the investigators have deemed to not interfere with the study's intervention or assessment (e.g. vitamins, omega-3, creatine monohydrate etc.), you will be permitted to continue taking these supplements. In all cases, participants will be instructed to not change the dose of the taken supplement or introduce a new supplement unless it is medically recommended.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Canada1 site, 1 recruiting
- Recruiting
University of Calgary
Calgary, Alberta, T2N 1N4
Jane Shearer, (403) 220-3431, jshearer@ucalgary.ca
About this study
Official title: Iron Revisited: Alternate-Day Oral Iron Supplementation in Endurance, Intermittent, and Power/Strength Athletes
The goal of this clinical trial is to learn if different types and doses of oral iron supplements can improve iron levels, athletic performance, and gut health in young female athletes with low iron stores. The main questions it aims to answer are:
- Does a low dose of yeast-bound iron improve iron status better than traditional iron supplements?
- Do the different iron supplements cause fewer or more gastrointestinal (stomach) symptoms?
- How do iron supplements affect exercise performance and gut bacteria?
Read more
Researchers will compare three types of iron supplements:
- A low-dose iron supplement (40 mg)
- A low-dose yeast-bound iron supplement (40 mg)
- A high-dose iron supplement (150 mg)
This will help researchers find out which type of supplement is most effective and easiest on the stomach.
Participants will:
- Take one of the three assigned iron supplements every other day for 12 weeks
- Complete fitness tests before and after the study, including cycling and jumping tests
- Give blood samples to measure iron levels
- Provide stool and intestinal samples to study gut bacteria
- Swallow a SIMBA capsule before and after the study to collect a sample from the small intestine
- Complete regular online surveys about sleep, stress, menstrual cycles, and gut symptoms
Read the detailed description
This clinical trial is designed to evaluate and compare the effects of three oral iron supplementation strategies on iron status, gut microbiota, and athletic performance in young female athletes with suboptimal iron levels. The study compares a low-dose iron supplement, a low-dose yeast-bound iron supplement (Lalmin® Fe10), and a high-dose iron supplement. The primary goal is to identify which iron supplement improves iron status most effectively while minimizing gastrointestinal symptoms and changes to the gut microbiota.
The rationale for the study is based on the high prevalence of iron deficiency among female athletes, especially those involved in endurance and high-intensity sports. Iron plays a key role in oxygen transport, energy production, and recovery, making it essential for optimal athletic performance. However, current supplementation practices often lead to poor compliance due to side effects and low absorption rates. The yeast-bound iron product being tested is hypothesized to improve absorption and tolerability by altering the site of absorption and reducing gastrointestinal distress.
Participants will be biologically female athletes aged 16-35 with suboptimal ferritin (≤50 µg/L), who are competitively trained and meet strict health and fitness criteria. After screening, eligible participants will be randomly assigned to one of three groups and consume their assigned supplement every other day for 12 weeks. Each supplement will be encapsulated to preserve blinding and consistency.
The study involves six in-person visits:
Visit 1 Screening and Consenting:
Study investigators will reach out electronically or by phone to individuals interested in participating in the study. At this time, participants will be informed about the study and eligibility will be confirmed. Iron status will be assessed using ferritin, achieved through a forearm venipuncture. Participants with suboptimal ferritin levels (≤50 µg/L) will be asked to complete a 3-day food record over the following week on non-consecutive days. This food intake data will be used to determine energy availability to ensure participants meet the minimum requirement of >30 kcal/kg lean body mass. Those who do not meet this requirement will be excluded from further participation.
Visit 2 Baseline Testing (Week 0):
Once inclusionary criteria has been confirmed and met, participants will undergo baseline measures of iron status through a forearm blood draw, they will complete a body composition assessment to assess lean body mass, and participants will complete a cycling-based aerobic fitness test (VO2 max) to characterize their fitness level. Participants will also be sent home with a package with SIMBA capsules, fecal sample collection kit, and collection instructions.
Visit 3 Baseline Testing (Week 0):
Participants will return 48-72 hours later to complete a cycling-based anaerobic fitness test (Wingate) and a countermovement jump test to assess fitness level. After fecal sample has been retrieved and picked up by study personal, participants will begin the 12-week nutritional intervention.
Nutritional Intervention:
Participants will consume an oral iron supplement every other day for 12 weeks. Participants will take their supplement within 30 minutes of morning training. If there is no morning training, participants will be instructed to consume immediately upon waking. The total dose of elemental iron is 40mg for the low dose group, 40mg for the yeast bound iron group, and 150mg for the high dose group, contained within a gelatin capsule. The iron-complexed yeast is a pasteurized (not live) Saccharomyces cerevisiae, a common nutritional yeast. There are no limits on how much can be consumed. They will also be reminded to take with food, a few hours before or after taking other medications or natural health products and avoid coffees, teas, dairy and dairy alternatives for two hours after consumption every other day. If they miss a dose, they will be recommended to take the next dose the next day and begin dosing every other day from there. After 4 and 8 weeks of consuming the supplement, participants will return to the lab for follow-up testing, consisting of a venipuncture blood draw (visits 4 and 5) and three-day food log (visit 4 only). At these visits they will be provided with another four-week supply of capsules. Participants will then be instructed to return to the lab to retrieve another 4 weeks of capsules, 8 weeks into the intervention, before completing their 12-week post-intervention tests. The Get Active Questionnaire (GAQ) and Menstrual Disorder of Teenagers (MDOT) will be completed at baseline; the Epworth Sleepiness Scale and Menstrual Bleeding Questionnaire will be completed monthly; the Gastrointestinal Symptoms Questionnaire, Post Exercise Short Recovery Scale, and Acute Recovery and Stress Scale will be assessed weekly through Qualtrics, an online survey platform.
Visit 4 Follow-Up (Week 4):
Participants will have a blood sample drawn for assessment of iron status and be instructed to complete a 3-day food log on three-non-consecutive days over the next week.
Visit 5 Follow-Up (Week 8):
Participants will have a blood sample drawn for assessment of iron to reduce the risk of iron overload.
Visit 6 Post Intervention (Week 12):
After the 12-week intervention has concluded, participants will return to the lab to repeat the aerobic exercise test (VO2).
Visit 7 Post Intervention (Week 12):
Participants will return to the lab to repeat measures done at baseline (blood status, body composition, anaerobic fitness test (Wingate and countermovement jump test), 3-day food log, fecal sample collection kit, and SIMBA capsule). At this time, participants will return any unused capsules to be counted for assessment of compliance.
Primary outcomes include changes in markers of iron status (ferritin, hemoglobin, RBC indices). Secondary outcomes include aerobic/anaerobic performance measures, body composition (DXA), substrate metabolism, gut microbiota composition (via fecal and intestinal sampling), and self-reported gastrointestinal symptoms. Safety and tolerability will be monitored at each study visit and through participant self-report.
Data will be analyzed using both traditional statistics (e.g., ANOVA) and machine learning methods for complex 'omics' data. Results will inform better supplementation strategies for female athletes and will be shared through academic publications.
The study will contribute to a greater understanding of iron supplementation strategies that are effective, tolerable, and beneficial to performance and health.
- Conditions
- Iron Deficiency
- Being tested
- Low-dose iron (ferrous sulfate), Yeast-bound iron (ferrous sulfate), High-dose iron (ferrous sulfate)
- Keywords
- iron, iron deficiency, athletic performance, female athlete, iron supplements, ferritin, hemoglobin, gastrointestinal, microbiome, Exercise test, Yeast, Saccharomyces cerevisiae, ferrous sulphate, ferrous sulfate, Body composition, exercise
- Medical subject headings
- Iron Deficiencies, Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Low-dose iron (ferrous sulfate)Dietary supplement
Encapsulated low-dose ferrous sulphate (40mg elemental iron)
Yeast-bound iron (ferrous sulfate)Dietary supplement
Encapsulated yeast-bound low-dose ferrous sulphate (40mg elemental iron)
High-dose iron (ferrous sulfate)Dietary supplement
Encapsulated high-dose ferrous sulphate (150mg elemental iron)
| Study group | Role | What they receive |
|---|---|---|
| Low dose iron supplement | Active comparator | This supplement consists of encapsulated ferrous sulphate (40 mg elemental iron). Receives: Dietary Supplement: Low-dose iron (ferrous sulfate) |
| Low dose iron supplement bound to yeast | Experimental | Low dose iron (40 mg elemental iron) in the form of yeast-bound iron, specifically Lalmin® Fe10. This supplement consists of encapsulated ferrous sulphate complexed with inactivated Saccharomyces cerevisiae (nutritional yeast). Receives: Dietary Supplement: Yeast-bound iron (ferrous sulfate) |
| High dose iron supplement | Active comparator | This supplement consists of encapsulated ferrous sulphate (150 mg elemental iron). Receives: Dietary Supplement: High-dose iron (ferrous sulfate) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Iron status blood markers
A forearm venous blood draw
Measured: Baseline
Iron status blood markers
A forearm venous blood draw
Measured: 4 weeks
Iron status blood markers
A forearm venous blood draw
Measured: 8 weeks
Iron status blood markers
A forearm venous blood draw
Measured: 12 weeks
Gut microbiota
Effects of the various iron formulations on the gut microbiota using the SIMBA capsule and stool sample analysis.
Fecal Collection: Participants will provide two stool samples to assess fecal metabolites and gut microbiota composition. Participants will be provided a stool sample collection kit that will allow them to collect the sample in the privacy of their home. The kit will contain all necessary instructions and materials required to perform the collection.
Gut microbiome Assessment: Participants will ingest a SIMBA capsule pre and post intervention. The capsule captures a small fluid sample from the small intestine, which will be retrieved upon excretion to examine the gut microbiome.
Measured: Baseline
Gut microbiota
Effects of the various iron formulations on the gut microbiota using the SIMBA capsule and stool sample analysis.
Fecal Collection: Participants will provide two stool samples to assess fecal metabolites and gut microbiota composition. Participants will be provided a stool sample collection kit that will allow them to collect the sample in the privacy of their home. The kit will contain all necessary instructions and materials required to perform the collection.
Gut microbiome Assessment: Participants will ingest a SIMBA capsule pre and post intervention. The capsule captures a small fluid sample from the small intestine, which will be retrieved upon excretion to examine the gut microbiome.
Measured: 12 weeks
Secondary outcomes (20)
VO2 Max
VO2 max testing on a cycling ergometer to assess peak power output, maximal oxygen consumption, and exercise thresholds.
Individuals will begin with a 4-minute warm-up of low intensity, then proceed to a progressively increasing cycling challenge until they reach the point of voluntary exhaustion. Breath-by-breath measurement of gas exchange will be captured using open-circuit spirometry at rest, during exercise, and during recovery. Perceptual responses will be recorded during warm-up, every two minutes throughout exercise, and after task failure. Heart rate will be collected using a chest strap and measured throughout exercise. This method is used to evaluate the fitness levels of the participants.
Metabolic cart measurements: Participants will wear a mask connected to a breath-by-breath metabolic cart to measure expired gases and minute ventilation. This equipment will continuously monitor the expired concentrations of O2 and CO2.
Measured: Baseline
VO2 Max
VO2 max testing on a cycling ergometer to assess peak power output, maximal oxygen consumption, and exercise thresholds.
Individuals will begin with a 4-minute warm-up of low intensity, then proceed to a progressively increasing cycling challenge until they reach the point of voluntary exhaustion. Breath-by-breath measurement of gas exchange will be captured using open-circuit spirometry at rest, during exercise, and during recovery. Perceptual responses will be recorded during warm-up, every two minutes throughout exercise, and after task failure. Heart rate will be collected using a chest strap and measured throughout exercise. This method is used to evaluate the fitness levels of the participants.
Metabolic cart measurements: Participants will wear a mask connected to a breath-by-breath metabolic cart to measure expired gases and minute ventilation. This equipment will continuously monitor the expired concentrations of O2 and CO2.
Measured: 12 weeks
Wingate
Wingate test completed on cycle ergometer to determine peak power output and fatigue index.
During this test, participants will use a cycle ergometer. After a five-minute warm-up at low intensity, participants will pedal at maximum effort against a set resistance (7.5%) for 30 seconds, based on their body weight. Peak power will be assessed as well as other key performance metrics.
Measured: Baseline
Wingate
Wingate test completed on cycle ergometer to determine peak power output and fatigue index.
During this test, participants will use a cycle ergometer. After a five-minute warm-up at low intensity, participants will pedal at maximum effort against a set resistance (7.5%) for 30 seconds, based on their body weight. Peak power will be assessed as well as other key performance metrics.
Measured: 12 weeks
Countermovement jump test
Researchers will use a force plate to assess low body and explosive strength. After a 10 minute warm-up where participants will perform 3 maximal CMJs, rest for two minutes, and perform a second set of 3 CMJs. Participants will complete 3-5 repetitions, with a minimum of 3, with 10-15 seconds between each jump, within a minimum of 10 seconds. Testing will occur before and after supplementation.
Measured: Baseline
Countermovement jump test
Researchers will use a force plate to assess low body and explosive strength. After a 10 minute warm-up where participants will perform 3 maximal CMJs, rest for two minutes, and perform a second set of 3 CMJs. Participants will complete 3-5 repetitions, with a minimum of 3, with 10-15 seconds between each jump, within a minimum of 10 seconds. Testing will occur before and after supplementation.
Measured: 12 weeks
Body composition
The DXA procedure uses a small amount of x-ray radiation to determine the amount of fat, bone, and muscle mass an individual has in his/her body.
Measured: Baseline
Body composition
The DXA procedure uses a small amount of x-ray radiation to determine the amount of fat, bone, and muscle mass an individual has in his/her body.
Measured: 12 weeks
Gastrointestinal Health
PROMIS and Gastrointestinal Symptom Questionnaire to assess gastrointestinal symptoms.
Measured: Weekly from baseline to 12 weeks
Menstrual cycle
MDOT questionnaire to assess menstrual cycle.
Measured: Baseline
Menstrual cycle
Menstrual Bleeding questionnaire to assess menstrual cycle.
Measured: baseline
Menstrual cycle
Menstrual Bleeding questionnaire to assess menstrual cycle.
Measured: 4 weeks
Menstrual cycle
Menstrual Bleeding questionnaire to assess menstrual cycle.
Measured: 8 weeks
Menstrual cycle
Menstrual Bleeding questionnaire to assess menstrual cycle.
Measured: 12 weeks
Short Stress and Recovery Scale (SSRS)
Short Stress and Recovery Scale (SSRS) to assess recovery and stress; higher scores under each domain indicate higher levels of stress or recovery, respectively
Measured: Completed weekly from baseline to 12 weeks
Activity Readiness
Get Active Questionnaire to assess readiness for exercise.
Measured: Baseline
Sleep
Epworth Sleepiness Scale (ES) to assess sleep; possible range 0-24; higher scores indicate higher levels of sleepiness
Measured: Baseline
Sleep
Epworth Sleepiness Scale (ES) to assess sleep; possible range 0-24; higher scores indicate higher levels of sleepiness
Measured: 4 weeks
Sleep
Epworth Sleepiness Scale (ES) to assess sleep; possible range 0-24; higher scores indicate higher levels of sleepiness
Measured: 8 weeks
Sleep
Epworth Sleepiness Scale (ES) to assess sleep; possible range 0-24; higher scores indicate higher levels of sleepiness
Measured: 12 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Apr 2025
- Study start26 Mar 2026
- Primary completionSep 2026 (estimated)
- Study completionSep 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (8)Papers the sponsor has linked to this study.
- Other trials for Iron DeficiencyStudies of the same condition, open and under way.
- More trials run by University of CalgaryThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 36 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Calgary
- Sponsor type
- University, hospital or other
- Collaborators
- Mitacs, Natural Sciences and Engineering Research Council, Canada
- Responsible party
- Principal investigator, Jane Shearer, University of Calgary
- Investigators
- Jane Shearer, Principal investigator, University of Calgary
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06942208
- Sponsor's protocol ID
- REB25-0095
- Acronym
- FeSc2
- Status last verified
- Apr 2026
- First submitted
- 9 Apr 2025
- Last updated
- 17 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Pantopoulos K. Oral iron supplementation: new formulations, old questions. Haematologica. 2024 Sep 1;109(9):2790-2801. doi: 10.3324/haematol.2024.284967.
PubMed 38618666McKay AKA, Stellingwerff T, Smith ES, Martin DT, Mujika I, Goosey-Tolfrey VL, Sheppard J, Burke LM. Defining Training and Performance Caliber: A Participant Classification Framework. Int J Sports Physiol Perform. 2022 Feb 1;17(2):317-331. doi: 10.1123/ijspp.2021-0451. Epub 2022 Dec 29.
PubMed 34965513McKay AKA, Sim M, Moretti D, Hall R, Stellingwerff T, Burden RJ, Peeling P. Methodological Considerations for Investigating Iron Status and Regulation in Exercise and Sport Science Studies. Int J Sport Nutr Exerc Metab. 2022 Apr 1;32(5):359-370. doi: 10.1123/ijsnem.2021-0343. Print 2022 Sep 1.
PubMed 35365588McCormick R, Moretti D, McKay AKA, Laarakkers CM, Vanswelm R, Trinder D, Cox GR, Zimmerman MB, Sim M, Goodman C, Dawson B, Peeling P. The Impact of Morning versus Afternoon Exercise on Iron Absorption in Athletes. Med Sci Sports Exerc. 2019 Oct;51(10):2147-2155. doi: 10.1249/MSS.0000000000002026.
PubMed 31058762Low MS, Speedy J, Styles CE, De-Regil LM, Pasricha SR. Daily iron supplementation for improving anaemia, iron status and health in menstruating women. Cochrane Database Syst Rev. 2016 Apr 18;4(4):CD009747. doi: 10.1002/14651858.CD009747.pub2.
PubMed 27087396Erdman KA, Fung TS, Doyle-Baker PK, Verhoef MJ, Reimer RA. Dietary supplementation of high-performance Canadian athletes by age and gender. Clin J Sport Med. 2007 Nov;17(6):458-64. doi: 10.1097/JSM.0b013e31815aed33.
PubMed 17993788Cordova A, Mielgo-Ayuso J, Fernandez-Lazaro CI, Caballero-Garcia A, Roche E, Fernandez-Lazaro D. Effect of Iron Supplementation on the Modulation of Iron Metabolism, Muscle Damage Biomarkers and Cortisol in Professional Cyclists. Nutrients. 2019 Feb 27;11(3):500. doi: 10.3390/nu11030500.
PubMed 30818782Attwell C, McKay A, Sim M, Dugan C, Nicholas J, Hopper L, Peeling P. Timing is everything, but does it really matter? Impact of 8-weeks morning versus evening iron supplementation in ballet and contemporary dancers. Eur J Sport Sci. 2023 Dec;23(12):2275-2282. doi: 10.1080/17461391.2023.2224285. Epub 2023 Jul 10.
PubMed 37291690
Study at a glance
From the registry record, last updated by the sponsor on 17 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Iron Revisited: Alternate-Day Oral Iron Supplementation in Endurance, Intermittent, and Power/Strength Athletes
- ClinicalTrials.gov ID
- NCT06942208
- Acronym / sponsor ID
- FeSc2 / REB25-0095
- Conditions
- Iron Deficiency
- Keywords
- iron, iron deficiency, athletic performance, female athlete, iron supplements, ferritin, hemoglobin, gastrointestinal
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 36 participants (estimated)
- Lead sponsor
- University of CalgaryUniversity, hospital or other
- Collaborators
- Mitacs, Natural Sciences and Engineering Research Council, Canada
- Study start
- 26 Mar 2026 (actual)
- Primary completion
- Sep 2026 (estimated)
- Study completion
- Sep 2026 (estimated)
- First posted
- 24 Apr 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this clinical trial is to learn if different types and doses of oral iron supplements can improve iron levels, athletic performance, and gut health in young female athletes with low iron stores. The main questions it aims to answer are:
- Does a low dose of yeast-bound iron improve iron status better than traditional iron supplements?
- Do the different iron supplements cause fewer or more gastrointestinal (stomach) symptoms?
- How do iron supplements affect exercise performance and gut bacteria?
Researchers will compare three types of iron supplements:
- A low-dose iron supplement (40 mg)
- A low-dose yeast-bound iron supplement (40 mg)
- A high-dose iron supplement (150 mg)
This will help researchers find out which type of supplement is most effective and easiest on the stomach.
Participants will:
- Take one of the three assigned iron supplements every other day for 12 weeks
- Complete fitness tests before and after the study, including cycling and jumping tests
- Give blood samples to measure iron levels
- Provide stool and intestinal samples to study gut bacteria
- Swallow a SIMBA capsule before and after the study to collect a sample from the small intestine
- Complete regular online surveys about sleep, stress, menstrual cycles, and gut symptoms
Detailed description
This clinical trial is designed to evaluate and compare the effects of three oral iron supplementation strategies on iron status, gut microbiota, and athletic performance in young female athletes with suboptimal iron levels. The study compares a low-dose iron supplement, a low-dose yeast-bound iron supplement (Lalmin® Fe10), and a high-dose iron supplement. The primary goal is to identify which iron supplement improves iron status most effectively while minimizing gastrointestinal symptoms and changes to the gut microbiota.
The rationale for the study is based on the high prevalence of iron deficiency among female athletes, especially those involved in endurance and high-intensity sports. Iron plays a key role in oxygen transport, energy production, and recovery, making it essential for optimal athletic performance. However, current supplementation practices often lead to poor compliance due to side effects and low absorption rates. The yeast-bound iron product being tested is hypothesized to improve absorption and tolerability by altering the site of absorption and reducing gastrointestinal distress.
Participants will be biologically female athletes aged 16-35 with suboptimal ferritin (≤50 µg/L), who are competitively trained and meet strict health and fitness criteria. After screening, eligible participants will be randomly assigned to one of three groups and consume their assigned supplement every other day for 12 weeks. Each supplement will be encapsulated to preserve blinding and consistency.
The study involves six in-person visits:
Visit 1 Screening and Consenting:
Study investigators will reach out electronically or by phone to individuals interested in participating in the study. At this time, participants will be informed about the study and eligibility will be confirmed. Iron status will be assessed using ferritin, achieved through a forearm venipuncture. Participants with suboptimal ferritin levels (≤50 µg/L) will be asked to complete a 3-day food record over the following week on non-consecutive days. This food intake data will be used to determine energy availability to ensure participants meet the minimum requirement of >30 kcal/kg lean body mass. Those who do not meet this requirement will be excluded from further participation.
Visit 2 Baseline Testing (Week 0):
Once inclusionary criteria has been confirmed and met, participants will undergo baseline measures of iron status through a forearm blood draw, they will complete a body composition assessment to assess lean body mass, and participants will complete a cycling-based aerobic fitness test (VO2 max) to characterize their fitness level. Participants will also be sent home with a package with SIMBA capsules, fecal sample collection kit, and collection instructions.
Visit 3 Baseline Testing (Week 0):
Participants will return 48-72 hours later to complete a cycling-based anaerobic fitness test (Wingate) and a countermovement jump test to assess fitness level. After fecal sample has been retrieved and picked up by study personal, participants will begin the 12-week nutritional intervention.
Nutritional Intervention:
Participants will consume an oral iron supplement every other day for 12 weeks. Participants will take their supplement within 30 minutes of morning training. If there is no morning training, participants will be instructed to consume immediately upon waking. The total dose of elemental iron is 40mg for the low dose group, 40mg for the yeast bound iron group, and 150mg for the high dose group, contained within a gelatin capsule. The iron-complexed yeast is a pasteurized (not live) Saccharomyces cerevisiae, a common nutritional yeast. There are no limits on how much can be consumed. They will also be reminded to take with food, a few hours before or after taking other medications or natural health products and avoid coffees, teas, dairy and dairy alternatives for two hours after consumption every other day. If they miss a dose, they will be recommended to take the next dose the next day and begin dosing every other day from there. After 4 and 8 weeks of consuming the supplement, participants will return to the lab for follow-up testing, consisting of a venipuncture blood draw (visits 4 and 5) and three-day food log (visit 4 only). At these visits they will be provided with another four-week supply of capsules. Participants will then be instructed to return to the lab to retrieve another 4 weeks of capsules, 8 weeks into the intervention, before completing their 12-week post-intervention tests. The Get Active Questionnaire (GAQ) and Menstrual Disorder of Teenagers (MDOT) will be completed at baseline; the Epworth Sleepiness Scale and Menstrual Bleeding Questionnaire will be completed monthly; the Gastrointestinal Symptoms Questionnaire, Post Exercise Short Recovery Scale, and Acute Recovery and Stress Scale will be assessed weekly through Qualtrics, an online survey platform.
Visit 4 Follow-Up (Week 4):
Participants will have a blood sample drawn for assessment of iron status and be instructed to complete a 3-day food log on three-non-consecutive days over the next week.
Visit 5 Follow-Up (Week 8):
Participants will have a blood sample drawn for assessment of iron to reduce the risk of iron overload.
Visit 6 Post Intervention (Week 12):
After the 12-week intervention has concluded, participants will return to the lab to repeat the aerobic exercise test (VO2).
Visit 7 Post Intervention (Week 12):
Participants will return to the lab to repeat measures done at baseline (blood status, body composition, anaerobic fitness test (Wingate and countermovement jump test), 3-day food log, fecal sample collection kit, and SIMBA capsule). At this time, participants will return any unused capsules to be counted for assessment of compliance.
Primary outcomes include changes in markers of iron status (ferritin, hemoglobin, RBC indices). Secondary outcomes include aerobic/anaerobic performance measures, body composition (DXA), substrate metabolism, gut microbiota composition (via fecal and intestinal sampling), and self-reported gastrointestinal symptoms. Safety and tolerability will be monitored at each study visit and through participant self-report.
Data will be analyzed using both traditional statistics (e.g., ANOVA) and machine learning methods for complex 'omics' data. Results will inform better supplementation strategies for female athletes and will be shared through academic publications.
The study will contribute to a greater understanding of iron supplementation strategies that are effective, tolerable, and beneficial to performance and health.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Low dose iron supplement | Active comparator | Dietary Supplement: Low-dose iron (ferrous sulfate)This supplement consists of encapsulated ferrous sulphate (40 mg elemental iron). |
| Low dose iron supplement bound to yeast | Experimental | Dietary Supplement: Yeast-bound iron (ferrous sulfate)Low dose iron (40 mg elemental iron) in the form of yeast-bound iron, specifically Lalmin® Fe10. This supplement consists of encapsulated ferrous sulphate complexed with inactivated Saccharomyces cerevisiae (nutritional yeast). |
| High dose iron supplement | Active comparator | Dietary Supplement: High-dose iron (ferrous sulfate)This supplement consists of encapsulated ferrous sulphate (150 mg elemental iron). |
Who may qualify
- Ages
- 16 to 35 years
- Sex
- Female only
- Healthy volunteers
- Accepted
- Age groups
- Child, Adult
Key inclusion criteria (12 listed)
- Biologically female athlete
- Age 16-35
- At least one year past the age of menarche
- Complete and pass the Get Active Questionnaire (GAQ)
- Suboptimal ferritin levels (≤50 mcg/L)
Key exclusion criteria (53 listed)
- Non-English speaking
- Anemic (hemoglobin <120g/L)
- Regular prebiotic (fiber) or probiotic use within 4 weeks of study enrollment
- Current laxative use
- Are a smoker or use tobacco products
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Low-dose iron (ferrous sulfate)Encapsulated low-dose ferrous sulphate (40mg elemental iron) | Dietary supplement | Low dose iron supplement |
| Yeast-bound iron (ferrous sulfate)Encapsulated yeast-bound low-dose ferrous sulphate (40mg elemental iron) | Dietary supplement | Low dose iron supplement bound to yeast |
| High-dose iron (ferrous sulfate)Encapsulated high-dose ferrous sulphate (150mg elemental iron) | Dietary supplement | High dose iron supplement |
Primary outcome
Iron status blood markers
Time frame: Baseline
A forearm venous blood draw
Iron status blood markers
Time frame: 4 weeks
A forearm venous blood draw
Iron status blood markers
Time frame: 8 weeks
A forearm venous blood draw
Iron status blood markers
Time frame: 12 weeks
A forearm venous blood draw
Gut microbiota
Time frame: Baseline
Effects of the various iron formulations on the gut microbiota using the SIMBA capsule and stool sample analysis. Fecal Collection: Participants will provide two stool samples to assess fecal metabolites and gut microbiota composition. Participants will be provided a stool sample collection kit that will allow them to collect the sample in the privacy of their home. The kit will contain all necessary instructions and materials required to perform the collection. Gut microbiome Assessment: Participants will ingest a SIMBA capsule pre and post intervention. The capsule captures a small fluid sample from the small intestine, which will be retrieved upon excretion to examine the gut microbiome.
Gut microbiota
Time frame: 12 weeks
Effects of the various iron formulations on the gut microbiota using the SIMBA capsule and stool sample analysis. Fecal Collection: Participants will provide two stool samples to assess fecal metabolites and gut microbiota composition. Participants will be provided a stool sample collection kit that will allow them to collect the sample in the privacy of their home. The kit will contain all necessary instructions and materials required to perform the collection. Gut microbiome Assessment: Participants will ingest a SIMBA capsule pre and post intervention. The capsule captures a small fluid sample from the small intestine, which will be retrieved upon excretion to examine the gut microbiome.
20 secondary outcomes
VO2 Max
Time frame: Baseline
VO2 Max
Time frame: 12 weeks
Wingate
Time frame: Baseline
Wingate
Time frame: 12 weeks
Countermovement jump test
Time frame: Baseline
Countermovement jump test
Time frame: 12 weeks
Body composition
Time frame: Baseline
Body composition
Time frame: 12 weeks
Gastrointestinal Health
Time frame: Weekly from baseline to 12 weeks
Menstrual cycle
Time frame: Baseline
Menstrual cycle
Time frame: baseline
Menstrual cycle
Time frame: 4 weeks
Menstrual cycle
Time frame: 8 weeks
Menstrual cycle
Time frame: 12 weeks
Short Stress and Recovery Scale (SSRS)
Time frame: Completed weekly from baseline to 12 weeks
Activity Readiness
Time frame: Baseline
Sleep
Time frame: Baseline
Sleep
Time frame: 4 weeks
Sleep
Time frame: 8 weeks
Sleep
Time frame: 12 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 17 Apr 2026.
- Background: PubMed 38618666Pantopoulos K. Oral iron supplementation: new formulations, old questions. Haematologica. 2024 Sep 1;109(9):2790-2801. doi: 10.3324/haematol.2024.284967.
- Background: PubMed 34965513McKay AKA, Stellingwerff T, Smith ES, Martin DT, Mujika I, Goosey-Tolfrey VL, Sheppard J, Burke LM. Defining Training and Performance Caliber: A Participant Classification Framework. Int J Sports Physiol Perform. 2022 Feb 1;17(2):317-331. doi: 10.1123/ijspp.2021-0451. Epub 2022 Dec 29.
- Background: PubMed 35365588McKay AKA, Sim M, Moretti D, Hall R, Stellingwerff T, Burden RJ, Peeling P. Methodological Considerations for Investigating Iron Status and Regulation in Exercise and Sport Science Studies. Int J Sport Nutr Exerc Metab. 2022 Apr 1;32(5):359-370. doi: 10.1123/ijsnem.2021-0343. Print 2022 Sep 1.
- Background: PubMed 31058762McCormick R, Moretti D, McKay AKA, Laarakkers CM, Vanswelm R, Trinder D, Cox GR, Zimmerman MB, Sim M, Goodman C, Dawson B, Peeling P. The Impact of Morning versus Afternoon Exercise on Iron Absorption in Athletes. Med Sci Sports Exerc. 2019 Oct;51(10):2147-2155. doi: 10.1249/MSS.0000000000002026.
- Background: PubMed 27087396Low MS, Speedy J, Styles CE, De-Regil LM, Pasricha SR. Daily iron supplementation for improving anaemia, iron status and health in menstruating women. Cochrane Database Syst Rev. 2016 Apr 18;4(4):CD009747. doi: 10.1002/14651858.CD009747.pub2.
- Background: PubMed 17993788Erdman KA, Fung TS, Doyle-Baker PK, Verhoef MJ, Reimer RA. Dietary supplementation of high-performance Canadian athletes by age and gender. Clin J Sport Med. 2007 Nov;17(6):458-64. doi: 10.1097/JSM.0b013e31815aed33.
- Background: PubMed 30818782Cordova A, Mielgo-Ayuso J, Fernandez-Lazaro CI, Caballero-Garcia A, Roche E, Fernandez-Lazaro D. Effect of Iron Supplementation on the Modulation of Iron Metabolism, Muscle Damage Biomarkers and Cortisol in Professional Cyclists. Nutrients. 2019 Feb 27;11(3):500. doi: 10.3390/nu11030500.
- Background: PubMed 37291690Attwell C, McKay A, Sim M, Dugan C, Nicholas J, Hopper L, Peeling P. Timing is everything, but does it really matter? Impact of 8-weeks morning versus evening iron supplementation in ballet and contemporary dancers. Eur J Sport Sci. 2023 Dec;23(12):2275-2282. doi: 10.1080/17461391.2023.2224285. Epub 2023 Jul 10.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Jane Shearer principal investigator
University of Calgary
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Low-dose iron (ferrous sulfate), Yeast-bound iron (ferrous sulfate) and High-dose iron (ferrous sulfate) in people with Iron Deficiency, run by University of Calgary at 1 site in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 12 inclusion and 53 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 17 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Lauren Hundseth ((306) 380-5898, lauren.hundseth@ucalgary.ca), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Iron status blood markers (time frame: Baseline). The study lists 6 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06942208, which also lists 8 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 17 Apr 2026.