Iron absorption and requirements in people living at high altitude
Iron Balance in Humans Living at High Altitude: Defining Requirements and Optimal Biomarker Thresholds Using a Novel Body Iron Labelling Technique Based on Stable Iron Isotopes.
This study will test whether healthy adults living at high altitude absorb and retain more dietary iron than adults at lower altitude by giving a small oral dose of a labeled iron and tracking blood changes.
Quick facts
| Phase | Not applicable |
|---|---|
| Study type | Interventional |
| Enrollment | 120 (estimated) |
| Ages | 18 Years to 45 Years |
| Sex | All |
| Sponsor | Swiss Distance University of Applied Sciences Academic / other |
| Locations | 1 site (Zurich, Canton of Zurich) |
| Trial ID | NCT07142590 on ClinicalTrials.gov |
What this trial studies
Researchers will recruit two groups of healthy adults in Switzerland—one living below 1000 m and one above 1500 m—with 60 participants per group (30 men and 30 women). Each participant will receive a single oral dose of stable 57Fe as ferrous sulfate with vitamin C, and blood samples will be collected during the second year at months 12, 16, 20 and 24 to measure isotopic enrichment and iron kinetics. Hemoglobin mass will be measured at two visits using a carbon monoxide rebreathing method, and no other interventions will be given. The aim is to define long-term iron absorption and losses at different altitudes to inform intake recommendations and diagnostic thresholds for iron deficiency.
Who should consider this trial
Good fit: Ideal participants are healthy non-smoking men and women aged 18–45 with BMI 18–25, body weight <70 kg for females or <85 kg for males, plasma ferritin >25 µg/L, normal hemoglobin, and willingness to attend follow-up visits over two years.
Not a fit: People with anemia, inflammation, chronic diseases affecting iron metabolism, pregnancy or lactation, recent participation in isotope studies, high physical activity, smokers, or those unable to give blood are unlikely to benefit or be eligible.
Why it matters
Potential benefit: If successful, the results could support altitude-adjusted iron intake recommendations and clearer diagnostic thresholds to better prevent and treat iron deficiency in high-altitude populations.
How similar studies have performed: Stable iron isotope methods are well-established for measuring absorption, but long-term iron-balance comparisons between residents at different altitudes are limited and relatively novel.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: * Females and males aged 18-45 y * BMI: 18 to 25 kg/m2 * Body weight \<70 kg for females, \<85 kg for males * Plasma ferritin \>25 µg/L * Signed informed consent Exclusion Criteria: * Hb \<12 g/dL (females), Hb \<13 g/dL (males), corrected for altitude using the 2024 WHO guidance values for hemoglobin adjustments * Inflammation (CRP \> 5 mg/L)1 * Plasma ferritin \>150 µg/L for females and \>200 µg/L for males * Chronic disease known to affect iron metabolism * Chronic medications (except for oral contraceptives) * Pregnancy (tested at screening) or intention to become pregnant during the course of the study * Lactation * High physical activity (MET-min/week \> 3000 calculated according to the IPAQ, short version, administered at the screening) * Difficulty with blood withdrawal * Earlier participation in a study using stable iron isotopes or participation in any clinical study within the last 30 days * Smoking * Blood donation, blood transfusion or significant blood loss (more than 400 mL) over the past 6 months * Intention to regularly donate blood during the 2 years duration of the study * No residence in the respective location/altitude for at least the last 2 years * No intention to reside in the respective location/altitude at least for the next 2 years * Participants who are planning to spend an extended period (\>12 weeks) at a different altitude from their residence location * Spending more than 2 nights per week at a different location from residence location * Inability to understand the information sheet and the informed consent form due to cognitive or language reasons
Where this trial is running
Zurich, Canton of Zurich
- Fernfachhochschule Schweiz (FFHS) — Zurich, Canton of Zurich, Switzerland (Recruiting)
Study contacts
- Principal investigator: Diego Moretti, Prof. Dr. — Fernfachhochschule Schweiz (FFHS), SUPSI
- Study coordinator: Nora Barloggio
- Email: nora.barloggio@ffhs.ch
- Phone: +41 44 512 10 01
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.