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Human milk is a white-blue liquid with a sweet taste. It weighs a little more than water. As all the other milks, it is an emulsion of fat particles in a fluid. It is generally composed as follows (but it changes from person to person and from the beginning to the end of breast feeding):

o       1-2% proteins

o       3-5% fats

o       6.5-10% carbohydrates

o       2% minerals

o       the rest is water.

The composition of the mother’s milk changes with the growth of the baby, adapting to the baby’s needs.

Proteins
The baby utilises the protein of mother’s milk at 100%. After the first days of life all the milk proteins become part of the baby; very few of them are eliminated. The baby nourished with cow’s milk, on the contrary, utilises only 50% of the milk proteins and eliminates about half of it from its diet.
The contribution in protein in mother’s milk is sufficient, while the protein excess of cow’s milk could be bad (possible renal damage) and cause poor assimilation. Cow’s milk contains four times the protein of human milk and must be diluted for the baby. Cow’s milk with a great quantity of casein, combined with the gastric juices, coagulates in a big thick clot in the stomach (curdled milk): this explains why babies feel satisfied for four hours after bottle feeding. The human curdled milk, on the contrary, is soft and light. The stomach of breast-fed babies empties quickly and easily, so the baby wants to feed more often. In this case it stimulates the production of more milk from the mother.
In mother’s milk there are 9 essential aminoacids, among them taurina which is very important for cerebretion, poor in neonatal time. Woman’s milk, not cow’s milk, is limited in aromatic aminoacids which could be dangerous for SNC when present in great haematic concentration.

Phenylalanine		Threonine
Isoleucine		Tryptophan
Leucine		Valine
Lysine		Methionine
Taurine

Water
Babies receive from mother’s milk a sufficient quantity of water for their metabolic needs. When it is hot, it’s the mother who needs a larger quantity of water and not the baby. The baby nourished with cow’s milk needs water for its metabolism and also for the kidneys to eliminate the salts and unnecessary proteins. So the baby needs water added to the artificial milk, and water directly from the bottle. The elimination of protein via the kidneys implies an effort.
For years it has been thought that premature babies grew better with artificial powdered milk; at last the researchers have realised that the increase in weight was due to water retention. That is the result of the immature kidneys which find it difficult to eliminate the superfluous protein and mineral salts.

Vitamins
Cow’s milk contains from half to a tenth of the essential vitamins in human milk. Even if the omnivorous mother eats cooked food, her milk contains more vitamins than cow’s milk because cows eat only grass. For this reason babies fed with artificial food need an integration of vitamins, or the diet must be varied. Breast-fed babies don’t require any other food up to the age of five or six months because milk is still full of vitamins, such as vitamin A and vitamin B which are fat-soluble.
Vitamin D controls the baby’s capacity to absorb calcium. In northern countries, vitamin D comes from the diet because the vitamin is synthesized by exposure to the sun. The lack of sun provokes rickets due to the lack of vitamin D. The breast-fed baby rarely develops rickets because mother’s milk has the right quantity of vitamin D.
Vitamin C is contained in great quantities in human milk, while it is almost absent in cow’s milk. The production of vitamin C by human mammary glands is so efficient that scurvy has never been observed in breast-fed babies, even if the mother is suffering from scurvy.

Vitamine A		Vitamine D
Vitamine C		Vitamine E

Fats
Cow’s milk and human milk have more or less the same quantity of fats. Cow’s milk has more saturated fats however, and that is why it is necessary to limit or avoid it after weaning.
The intestinal absorption of lipids after a week of life is 90% in human milk and 60% in cow’s milk. The concentration of fats increases towards the end of sucking so the baby feels satisfied. That is not possible with artificial food, so the baby eats more because its stomach feels empty.

Minerals
Calcium and phosphorus are in a smaller quantity in mother’s milk compared with artificial milk, but they are better absorbed.
Sodium, chlorine and potassium are in a smaller quantity in mother’s milk but the removal of electrolytes is easier.
In mother’s milk there is little iron but the same is true of cow’s milk. That is positive, because there is a reserve of iron in the baby’s liver and spleen, and there is also a high concentration of red blood cells which decrease after some time. If the mother is not anaemic during the pregnancy, the baby’s iron reserve is enough for the first year of life.
There is more copper in human milk; the level of zinc is the same in both mother’s milk and cow’s milk.

Sugars
The quantity of sugar is much higher in mother’s milk than in cow’s milk. The quality is different too. Sugar is lactose with a small quantity of other oligosaccharides. Lactose is easy to digest and improves the use of protein.

The high concentration of lactose can help the absorption of calcium. It is dangerous for the baby’s growth to add normal sugar to cow’s milk in order to increase glucose.

Immunological aspects
Breast-feeding has a protective function against viral, respiratory and intestinal infections. In mother’s milk there are antibodies against some viruses (polio, flu) and bacteria (tetanus, streptococcus, staphylococcus, salmonella). Mother’s milk offers good protection against allergies, which are less frequent in breast-fed babies.