When we compare the components of manufactured formula to breastmilk we find the following:
Formula contains an excess amount of protein (1.8 times), vitamin E (3.2 times), vitamin K (25.7 times), riboflavin (3.2 times), niacin (3.5 times), folic acid (2 times), vitamin C (1521 times), calcium (2.8 times), sodium (1.7 times), potassium (1.5 times), iron (35 times), and zinc (4.2 times), and an insufficient amount of vitamin B12, vitamin B6, beta-carotene, cholesterol, and fat among other things.
These artificially created vitamins and minerals are not absorbed as well into the body of a baby and therefore more may be necessary to provide nutrition. But how do you know that YOUR baby is getting what YOUR baby needs at each feeding? Breastmilk on the other hand changes on a daily and even more frequent basis to adapt to EXACTLY what YOUR baby needs at each and every feeding.
Source: Breastfeeding Physiology Student Manual, Childbirth International