Iron absorption and requirements in people living at high altitude

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

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.

Why it matters

Who can join: the full rules

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 it's running

• 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

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.