Vitamin D is known to play an important role in bone metabolism through regulation of calcium and phosphate homeostasis and may also play an important role in immune system regulation. Vitamin D is produced by the body during exposure to sunlight, but is also found in oily fish, eggs and fortified food products.

Infants are born with low vitamin D stores and are dependent on breast milk, sunlight or supplements as sources of vitamin D in the first few months of life. As the vitamin D content of breast milk is dependent on maternal vitamin D status and is often low, and sun exposure may be restricted for infants living at higher latitudes or for cultural or other reasons, infants are particularly vulnerable to vitamin D deficiency. Vitamin D deficiency in infants can lead to bone malformation (rickets), seizures and difficulty breathing.

Current evidence suggests that vitamin D supplements may be effective in preventing rickets, particularly for infants and children who may be at higher risk due to limited sun exposure or those with darker skin pigmentation, however further research is needed before specific recommendations can be made.