Lipids are the second largest component in breast milk. They are the principal source of energy for the baby and provide vital nutrients, fat soluble vitamins and polyunsaturated fatty acids. Lipids are the most variable component in breast milk with the highest caloric value. Triglycerides are the main fat element and are quickly broken down to free fatty acids and glycerol by lipase.
Breast milk lipids include preformed long-chain polyunsaturated fatty acids (in other words, DHA and ARA, which assist in the development of healthy nerve and brain tissue) which act as precursors for the development of prostaglandins and prostacyclins and other lipid mediators, in addition to other vital components in thin layers of essential tissues, such as the brain and the retina. Long-chain polyunsaturated fatty acids are necessary structural components of every cellular membrane and they aid in adjusting particular cell processes.
The ratio of polyunsaturated to saturated fat is low, which is beneficial to the retention of calcium. The cholesterol content is fairly high and it is closely associated with myelination.
Sources:
Boersma ER, Offringa PJ, Muskiet FAJ, Chase WM, and Simmons IJ. "Vitamin E, lipid fractions, and fatty acid composition of colostrum, transitional milk, and mature milk: an international comparative study." American Journal of Clinical Nutrition 1991 53(5):1197-1204. Jorgensen MH, Lauritzen L and Michaelsen KF. "Does Human Milk DHA Level Affect Functional Outcome in Infants?" Journal of Human Lactation, 15(1), 3-6. 1999. Koletzko B and Rodriguez-Palmero M. "Polunsaturated Fatty Acids in Human Milk and Their Role in Early Infant Development". Journal of Mammary Gland Biology and Neoplasia. 4(3), 269-284. 1999.
