Vitamin D is very important for a baby’s health and development as it aids the immune system to fight off infections. It is also responsible for maintaining the calcium and potassium levels in the blood required by the baby to build strong bones and teeth. It is essential for body mineral balance and blood clotting and it contributes to the heart and nervous system. It also maintains insulin levels.
Babies who do not get enough vitamin D3 may suffer from rachitis (rhachitis) which is a disease of the bones called rickets in some literature. Rachitis is a serious issue because it causes defective mineralization or calcification of bones in young babies due to deficiency or impaired metabolism of vitamin D, phosphorus and calcium, potentially leading to fractures and deformity.
Rachitis is more common in developing countries due to poor diet. However, it is important to note that breast-fed babies do not receive enough vitamin D3 through the breast milk even if the mother takes D3 supplements. The sun exposure is an important source of vitamin D, however, this exposure is not enough to fill the reservoirs of vitamin D in the baby’s body.
Young babies should not be exposed to the sun for long periods so it is therefore advised that breast-fed babies take D3 drops in milk daily to prevent this serious disease. Dark skinned mothers and babies are at the greater risk because they produce less vitamin D than those with lighter skin, for the same amount of sunlight.
There are many studies relating to this issue and one of them can be accessed by clicking here; http://www.ncbi.nlm.nih.gov/pubmed/24192675
On the other hand, bottle-fed babies usually do not need vitamin D supplementation as infant formula is fortified to meet the requirements for vitamin D intake.