Iron

Iron is an essential component of haemoglobin; the oxygen carrying component of red blood cells and myoglobin in muscle. It also has a role in many of the metabolic processes in the body, including energy metabolism and electron transfer¹.    

Iron is very important during infancy as it’s a key nutrient for brain function and development². The uptake of iron into the brain is at its greatest during the rapid period of brain growth which occurs in the first two years of infancy. At birth the brain has only reached 27% of its adult size and it continues to grow rapidly for the next two years³. A lack of iron in the diet of infants in their early years has been linked with problems in cognitive and behavioural functioning in later life^4,5.  

While the iron content of breast milk is low, it’s well utilised by the body. Breastfed infants absorb approximately 50% of the iron in breast milk⁶, whereas formula fed infants only tend to absorb about 10% of the iron in formula, hence there are higher levels of iron in formula than in breast milk⁶. 

In the first 4-6 months of life, babies rely on their own body stores for iron. However, from 4-6 months of age, infants’ iron stores begin to run out, so they need to get a good supply of iron from dietary sources⁷.   

Calcium and phosphorus

Calcium is essential for bone mineralisation and teeth development, making it a key nutrient for infants. In fact, 99% of the body’s calcium is deposited as calcium salts within the matrix of the bones and teeth, and this provides their structural rigidity^1,8. Within the first year of life the skeletal mass of an infant doubles, highlighting the importance of an adequate calcium intake⁹.

The remainder of the body’s calcium is found within tissue and body fluids where it plays a key role in cell membrane transport and stability¹. Calcium also plays a role in regulating muscle contraction, nerve transmission and blood clotting^1,10.  

Phosphorus is another key nutrient involved in bone mineralisation. The levels of phosphorus found within the body’s bones are approximately 85%¹. The rest of the phosphorus in the body is found in substances such as phospholipid membranes and within DNA and RNA. Phosphorus plays a key role inside cells which are associated with energy metabolism¹¹  in the release of energy and oxygen to the cells^11,12.     

During infancy and childhood, it’s important that there are appropriate levels of calcium and phosphorus in an infant’s diet to achieve optimum bone mineralisation.  

Zinc

Zinc is important for growth and muscle development. It’s also essential for the synthesis of lean tissue1 and plays a role in both DNA and RNA synthesis and cell division¹³. During infancy there’s a massive amount of cell division. Therefore it’s crucial that infants have sufficient zinc in their diet to achieve normal growth and development¹⁴.

Zinc also plays a role in supporting the immune system. It affects the integrity of the epithelial barrier and the function of white blood cells such as neutrophils, monocytes and macrophages¹⁵. Many of the body's hormones and enzymes also need zinc to function normally¹⁶. It’s important for both infants and adults to have an adequate intake of zinc as the body has no specialised zinc storage system¹⁷.  

Summary

Minerals are required for normal body function and are particularly important during the rapid period of growth during the first two years of infancy. Breast milk contains the optimum balance of nutrients required for optimal growth and development^18-22. For those babies whose mothers cannot or choose not to breastfeed, all necessary vitamins and minerals are added to infant formula to make it nutritionally complete.