A newborn infant at term contains about thirty grams of calcium. At the end of adolescence, there may be more than a kilogram. It is distributed in three main compartments : the skeleton, the extracellular space and the cells. The first two were the earliest to be studied and are the best understood because they are easier to investigate.
Bone provides attachment for muscles involved in movement, supports soft tissues, protects the nervous system and hemapoietic tissue, and plays an important role as a large store of calcium and phosphorus that can be used to maintain normal con-centrations of these elements in the blood.
When evaluating calcium needs in infants, two main variables have to be considered: 1. calcium requirement for growth, and 2. availability of dietary calcium. Evaluations of calcium and phosphorus requirements in infants and children are derived mainly from data of lean body mass  and metabolic balances [2, 3], and involve several assumptions , since body minerai content is only known for newborns, adults, and one 4 1/2 year child .
Six hundred-eight children, five years old or younger, hospitalized with respiratory syncytial virus infection, were prospectively studied to evaluate the relation between their immune status and the severity of their infection.
The growth which occurs throughout infancy, implies a daily gain of materials in the organism. By the last stage of adolescence, the newborn infant's total calcium content of 30 g will have risen to the normal adult content of 1100 g . All the calcium required for full development, principally in the skeleton, which is quantitatively and qualitatively distinct from intra-cellular ionic "messenger calcium", cornes from external sources, from food.