Despite the fact that the skeleton is mainly formed by a mineral framework, bone is a living, active tissue, metabolically active and in constant transformation. Bone is composed of a collagen framework permeated with mineral salts composed of mostly calcium and phosphate, together with trace amounts of other minerals and ions.
The skeleton needs a constant supply of nutrients. A healthy, balanced diet containing both macro – and micronutrients plus sufficient energy is vital for both the normal development and on-going maintenance of the skeleton.
Calcium accounts for 1 – 2% of the adult human’s body weight. The adult human body contains about 1200g of calcium. Of this amount, over 99% is found in mineralised tissues, such as bones and teeth.
The amount of calcium needed changes throughout the different stages of life. In the pre-pubescence years calcium requirements are high due to rapid growth of the skeleton. Milk and other dairy products are the most important sources of calcium. Other good food sources of calcium include some green vegetables, like broccoli; canned fish with soft edible bones, such as sardines, pilchards and salmon; nuts – especially Brazil nuts and almonds; and some fruit, such as oranges and apricots.
There is a wide variation in estimates of calcium requirements made by different expert authorities. Much of this divergence arises because of different interpretations of available human calcium balance data. The recommended nutrients intake as published by National Coordinating Committee on Food and Nutrition children and adolescents are as following:
1 – 3 years 500mg/day
4 – 6 years 600mg/day
7 – 9 years 700mg/day
10 – 18 years 1,000mg/day