One thing breast milk lacks that formula makes up for: vitamin D. Because many mothers are weak in this substance, their breast milk is insufficient as well, and their kids suffer as a result. According to one research, formula-fed babies had better bone mineralization (stronger bones) than breastfed babies, which is why the American Academy of Pediatrics recommends that breastfed kids take vitamin D supplements to compensate (ideally getting 400 IU per day in the first two months of life). Formula-fed newborns, on the other hand, are in good health as long as they consume 1 litre of infant formula every day.