Iron deficiency is considered the most common nutritional deficiency worldwide and affects children and women in both non-industrialized as well as industrialized countries. The main regulatory molecule of iron metabolism is hepcidin, a hormone produced in the liver that regulates intestinal iron absorption, placental transport, recycling of iron by macrophages and release from stores. The expression of hepcidin is regulated by many mediators, one of which is Matriptase-2 - a transmembrane protease. Complete loss of function leads to the rare disease iron-refractory iron deficiency anemia (IRIDA). Matriptase-2 is encoded by the gene TMPRSS6 and the single nucleotide polymorphism (SNP) rs855791 causes a non-synonymous substitution (V736A) that reduces the activity of the protease to inhibit hepcidin transcription. Genome wide association studies have identified the TMPRSS6 SNP rs855791 has a strong association with red blood cell and iron parameters in the general population.

The objectives of the study is to measure oral iron absorption and systemic iron utilization into red blood cells (RBC) using oral isotopic labels in subjects homozygotes for common variants of the TMPRSS6 gene with the SNP rs855791 (A736V); AA vs. VV subjects.

The aim is to conduct an iron absorption study in 80 Taiwanese women of reproductive age, non-pregnant, non-anemic, investigating the effect of the genetic variants of the SNP rs855791. The participants will be split in two groups of equal size; wild type AA vs. mutation VV. Iron absorption and systemic utilization will be assessed by two test meals containing stable isotopes of iron.The primary outcome of the trial is the oral iron absorption from a test meal as compared between the two genotypes AA vs. VV. Secondary outcomes are the comparison iron status markers between the two genotypes.

Inclusion Criteria:

• Subjects homozygotous for the for AA (CC), or VV (TT) variant of the SNP rs855791 of the TMPRSS6 gene.
• Females 20 - 45 years of age (premenopausal status)
• obtained informed consent
• regular menstrual cycle, ± 2 days

Exclusion Criteria:

• Pregnancy or lactating (assessed by pregnancy test and self-declaration, respectively)
• Anemia defined as Hb < 120 g/L
• Plasma ferritin < 30 µg/l, or > 120 µg/l
• C-reactive Protein > 5 mg/l
• Body weight > 65 kg
• Body mass index (BMI) 18.5 - 25
• Diagnosed metabolic or gastrointestinal disorders, eating disorders or food allergy to the ingredients of the test meal.
• Blood transfusion, blood donation or significant blood loss (accident, surgery) over the past 6 months, prior the first study day.
• Subjects who cannot be expected to comply with study protocol (e.g. non-residents).
• Use of long-term medication during the study
• Subjects that will take part of another clinical study at the same time or had within the last 30 days before the first study day
• Intake of mineral/vitamin supplements 2 weeks before the first study day and during the study