Albertine Donker

Chapter 2 60 height range based on the length of the parents. 58 ID, whether or not in the context of undernutrition, is also such an organic threat that may have longlasting effects on growth and development. Growth implies a huge expansion of blood volume requiring large amounts of iron The enormous growth that occurs from fetus to adult is accompanied by a 15-20 times expansion of the blood volume from an average of 240-250 mL at birth to an average of 4-5 liters in adulthood. To meet the iron demand for both growth-related increase of the blood volume and for the substitution of the recycled erythrocytes, the daily requirements for nutrients and also for iron is therefore relatively greater for children than for adults that only have to replace senescent erythrocytes. 59 For example, a 3 kg neonate requires approximately 0.2-0.3 mg iron (0.07-0.1 mg/kg) per day, while a 70 kg male adult requires 0.4-1.6 mg (0.01-0.02 mg/kg) per day ( Figure 1, Table 2 ).This makes children vulnerable to IDA, affecting hundreds of millions of children. 60,61 Iron is essential for bone formation Bone is a metabolically highly active tissue that is continously being remodeled, enabling growth in children as well as repair and adaptation of the skeleton in adults. Increase of the bone mass in childhood is paramount in order to support the growing body, but also to expand the environment for hematopoiesis in the red marrow inside the bones. 62 During the first two decades of life, the skeleton grows tremendously. 63 Around the age of 30, bones reach their maximum size, strenght and density, known as peak bone mass. 63 Since later in life the loss of bone exceeds the rate of bone replacement, lifelong bone health is strongly dependent on this maximum bone mass that is formed during the critical period of growth and maturation in childhood, adolescence and early adulthood. 63 A complex interaction of genetic, behavioral and environmental factors determine the bone mass. 64 Genetic traits contribute to approximately 60-80%, while physical activity and nutrition are responsible for the remaining 20-40% of variation in peak bone mass. 64 Although in particular calcium, phosphate and vitamin D play a crucial role in the formation of bone, other nutrients as vitamin K, copper, magesium, manganese, zinc and also iron are important for bone health. 64,65