Surprisingly, proteins are only 0.8 to 0.9% of the content of breast milk. The main proteins are: casein, serum albumin, a-lactalbumin, B-lactalbumin, immunoglobulins, and other glycoproteins; 40% of breast milk protein is casein, which contains equalized amino acids and provides calcium and phosphate; 60% is whey, which contains water, electrolytes and protein. Whey is made up of 5 factors: a-lactalbumin, serum albumin, lactoferrin, immunoglobulins and lysozyme.
Some proteins are not nutritionally available, but they do serve as immunological components. Amino acids are the building blocks of protein and 8 of the 20 amino acids in breast milk are vital and come from plasma. Mammary alveolar epithelium (the thin tissue that surrounds the milk-producing cells in the breast) integrate some of those amino acids.
Here are some of the essential amino acids:
- Taurine is the second most common amino acid found in breast milk. It is nonexistent in cow's milk. It functions as a neurotransmitter or a neuromodulator in the brain and retina. In addition, it supports conjugation of bile acids. Many companies are adding this amino acid to formula now.
- Nucleotides are significant in protein synthesis and they promote growth and differentiation of organs and tissues. They also improve the metabolism of lipids. There are 10 times more nucleotides in breast milk than in cow's milk.
- Carnitine is vital for catabolism of long chain fatty acids.
Source:
Velona T, Abbiati L, Berreta B, Gaiaschi A, Flauto U, Tagliabue P, Galli CL and Restani P. "Protein Profiles in Breast Milk from Mothers Delivering Term and Preterm Infants." Pediatric Research. 45(5), 658-663. 1999.
