The components of human breast milk differ greatly from cow’s milk. Cow’s milk is made for calves and human milk is made for human babies. Most artificial infant formula is based on cow’s milk.
The major nutrients in breastmilk are carbohydrates, lipids (fats) and proteins. Human milk contains two types of protiens, curds and whey. Cow’s milk has them too, but in a very different ratio. Human milk is 60% whey and 40% curds. Cow’s milk is 20% whey and 80% curds. The large percentage of curds in cow’s milk makes iron difficult for babies to absorb.
Artificially fed babies have to digest significantly more protein than breastfed babies. Human milk has lower levels of protein, calcium, sodium, potassium and other ions. (From Marie Biancuzzo’s Breastfeeding the Newborn). This means that breastfed babies’ kidneys work half as hard as artifcially fed babies’ kidneys. Premature babies have kidneys that get stressed much faster than a full-term baby’s does. For a premature baby who is formula fed, that can mean very serious health problems.