In the U.S., Enfamil was reformulated to have a 60:40 whey-to-casein protein component, similar to that of typical mature human milk (15 days to six months after birth). A few months later, the company introduced Enfamil Human Milk Fortifier, which when added to breast milk increased levels of protein, calories, iron, calcium, phosphorus, vitamins and other nutrients for premature and low-birth-weight babies.