The American Academy of Pediatrics (AAP) recommends that exclusively or primarily breastfed infants receive 400 IU (10 μg) a day of vitamin D for the first year of life and that toddlers and older children receive 600 IU (15 μg) a day. This is to prevent the consequences of vitamin D deficiency (particularly rickets), since human milk and most foods are inadequate sources of vitamin D, and the majority of infants and children do not get enough sun exposure to produce all the vitamin D that they need.[1]
There are two important exceptions to this vitamin D supplementation recommendation. First, formula-fed infants that consume at least 32 oz of formula per day usually do not require supplementation, since most formulas are fortified with vitamin D. Second, if a lactating parent is supplementing with 6400 IU (160 μg) a day of vitamin D, studies find that enough vitamin D passes into the breastmilk to negate the need for direct infant supplementation.[2]
Vitamin D toxicity in children is rare, but not impossible. Toxicity usually occurs with accidental ingestion of large doses of supplemental vitamin D, as found in a case series of 7 children who consumed between 266,000 and 800,000 IU (6,650–20,000 μg) a day due to erroneously manufactured supplements.[3]
Vitamin D supplementation in infants and children should be discussed with a clinician, especially if there are concerns about vitamin D serum levels. A clinician can order blood work to better guide any supplement decisions.