Iron deficiency (ID) is the most common micronutrient deficiency in the world. Iron is involved in oxygen transport, energy
metabolism, immune response, and plays an important role in brain development. In infancy, ID is associated with adverse effects
on cognitive, motor, and behavioral development that may persist later in life, despite iron supplementation. On the other
hand, iron is essential for the growth of bacteria, and is a pro-oxidant that can catalyze the formation of oxidative radicals
that damage proteins, lipids and nucleic acids. Iron supplementation in iron-replete children may have adverse effects, e.g.
increased risk of infections and impaired growth. Thus, the therapeutic range of iron is small, and prevention of both ID
and iron overload is essential for optimal development.
Aim of this thesis was to investigate the prevalence and risk
factors of ID and iron deficiency anemia (IDA) in children living in a high-income country. Furthermore, we aimed to analyze
the value of different iron status biomarkers in the diagnosis of ID. The studies described in this thesis focused on children
who are thought to have an increased risk of ID, namely preterm infants (part I), healthy children aged 0.5 to 3 years (part
II), and children with cystic fibrosis (CF) (part III).