Which vitamin supplement should be given to a 1-month-old exclusively breast-fed infant?

In this scenario, vitamin D is the correct supplement to be given to a 1-month-old exclusively breast-fed infant. Breast milk, while nutritionally complete in many aspects, typically does not provide enough vitamin D to meet an infant's needs for proper bone development and to help prevent conditions like rickets. Since sunlight exposure, which helps the body synthesize vitamin D, is limited especially in infants and considering concerns around sun safety, pediatric guidelines recommend that exclusively breast-fed infants receive a daily vitamin D supplement to ensure they have adequate levels.

While vitamin A, vitamin C, and vitamin B12 are also important for overall health, the specific recommendation regarding vitamin D stems from its unique role and necessity for rapidly growing infants, particularly those who do not receive formula or other sources fortified with this nutrient. Therefore, vitamin D is emphasized as a crucial supplement during the early months of life for infants who are being exclusively breast-fed.