Iron deficiency (ID) with or without anaemia (IDA) is a major public health problem worldwide, especially in women of reproductive age and young children. Iron supplementation is an effective strategy to prevent and treat ID and IDA. There is a lack of data on iron bioavailability from different supplementation regimens and how to optimize bioavailability in a cost-effective and patient-friendly way. The present study will test whether the fractional and total iron absorption from iron supplements (60 mg) administered daily for 14 days differs from that of iron supplements (60 mg) administered every second day for 28 days. The prevailing serum hepcidin concentration (SHep) is the major determinant of iron absorption and erythrocyte iron utilization. Therefore we will monitor SHep during the whole supplementation period. We hypothesize that the fractional and total iron absorption from the daily administration of 60 mg is lower than that from the administration on every second day due to increased SHep levels when supplements are administered daily.

The study will provide important insights about the optimization of iron bioavailability from different supplementation regimens including the performance of SHep, a key regulator of human iron metabolism.

Inclusion Criteria:

• Female, 18 to 45 years old,
• Serum ferritin levels </=25 µg/L,
• Normal body Mass Index (18.5-26.5 kg/m2),
• Body weight <80 kg,
• Signed informed consent

Exclusion Criteria:

• Anaemia (Hb < 8.0 g/dL),
• Elevated c-reactive protein or alpha1-glycoprotein concentrations >5.0 mg/L, >1.0 g/L, respectively,
• Any metabolic, gastrointestinal kidney or chronic disease such as diabetes, renal failure, hepatic dysfunction, hepatitis, hypertension, cancer or cardiovascular diseases (according to the participants own statement),
• Continuous/long-term use of medication during the whole studies (except for contraceptives),
• Consumption of mineral and vitamin supplements within 2 weeks prior to 1st supplement administration,
• Blood transfusion, blood donation or significant blood loss (accident, surgery) over the past 4 months,
• Earlier participation in a study using stable iron isotopes,
• Known hypersensitivity or allergy to iron supplements,
• Women who are pregnant or breast feeding,
• Intention to become pregnant during the course of the studies,
• Lack of safe contraception, defined as: Female participants of childbearing potential, not using and not willing to continue using a medically reliable method of contraception for the entire study duration, such as oral, injectable, or implantable contraceptives, or intrauterine contraceptive devices, or who are not using any other method considered sufficiently reliable by the investigator in individual cases.
• Known or suspected non-compliance, drug or alcohol abuse,
• Inability to follow the procedures of the studies, e.g. due to language problems, psychological disorders, dementia, etc. of the participant,
• Participation in another study with investigational drug within the 30 days preceding and during the present studies,
• Enrolment of the investigator, his/her family members, employees and other dependent persons