American Academy of Pediatrics has reported that all infants, particularly those who are breastfed, should be given vitamin D to help prevent rickets, a potentially crippling condition in which the bones fail to grow straight and strong. While breast milk is the best nutrition for babies, it may not contain enough vitamin D to meet babies needs. This happens particularly when youngsters are protected from sunlight, a natural source of the vitamin D. All infant formula sold in the U.S. contains added vitamin D, but if a baby drinks less than 500 milliliters of formula each day they should also receive supplements, according to the AAP.
Vitamin D supplements are also recommended in children and teens who do not drink at least 500 milliliters each day of milk fortified with vitamin D. Sunlight is a major source of vitamin D and early humans likely had skin that was better suited
to their environment, which enabled them to spend enough time in the sunlight to make lots of vitamin D without worrying about skin cancer. Numerous studies have linked nursing to a host of health benefits, such as higher IQ and a lower risk of sudden infant death syndrome, diabetes and chronic digestive diseases. However asking mothers to take extra vitamin D will not solve the problem, for the amount needed to satisfy nursing infants is "close to the toxic level" in mothers.