Calcium is a key nutrient for infants as it is essential for bone mineralisation and teeth development.   In fact approximately 99% of the body’s calcium is deposited as calcium salts within the matrix of the bones and teeth and this provides the structural rigidity^{1, 2}. Within the first year of life the skeletal mass of an infant doubles, this highlights the importance of an adequate calcium intake³.  

Calcium cannot be made in the body and therefore it is essential that an infant receives all of their calcium requirements from their diet.  Low intakes of calcium has  implications for bone mass as the amount of calcium consumed within the diet influences the amount of calcium that can be retained within the skeleton during rapid periods of growth^4,5.  The dietary intake and absorption of calcium also needs to be adequate to satisfy the losses of calcium predominately in the urine, sweat and faeces⁶.    

The body needs calcium not only for its skeletal functions, but also for non-skeletal functions.  Calcium is found within the tissue and body’s fluid where it plays key structural roles in cell membrane transport and stability¹.  Calcium also has the regulatory roles of regulating muscle contraction, nerve transmission and also blood clotting^{1, 7}.  Calcium ions are required for the blood clotting (coagulation) process and a decrease in levels of plasma calcium are associated with a reduced ability to form blood clots⁸.  In fact changes to either the structural and/or the regulatory roles of calcium can have implications for later health⁴.    

It is important that there is adequate calcium absorption during infancy.  The levels of calcium are lower in breast milk than in infant formula or cows’ milk but calcium in breast milk is better absorbed than cows’ milk or formula⁴.  To compensate for this difference, formula milks contain additional calcium⁴.  Like breast milk, formula milks also contain lactose. Lactose is a disaccharide, comprised of two sugars, glucose and galactose, and is unique to milk as it does not occur naturally elsewhere in nature.  As well as providing an energy source, lactose aids the absorption of minerals such as calcium⁹.  

The difference in the absorption of calcium between breastfed infants and formula fed infants may be due to both the positioning of the fatty acids within the triglycerides in breast milk, along with the favourable calcium to phosphorus ratio in breast milk⁴.  Studies have demonstrated that infants fed formula where the positioning of the fatty acids are more similar to that in breast milk, i.e. where there is an increased proportion of palmitic acid at the sn-2 position, resulted in an improved calcium absorption^10-13 and one study has shown an improved bone mineralisation¹⁴.

Calcium is essential for bone mineralisation and teeth development.  It also plays a regulatory role in a number of functions including muscle contraction, digestion and blood clotting.  During infancy it is important to have an adequate intake of calcium; a low intake during infancy has implications for bone mass and bone health in later life.