Colostrum is the breast milk produced during the first few days (1-5 days) after birth. It differs from transitional and mature milk. It contains a higher amount of protein, less fat and is rich in ingredients that support the immune system of your baby (like antibodies). Colostrum is very easily digestible and produced in small quantities, so your baby may nurse every two to three hours.

Transitional milk replaces colostrum within a week of childbirth. The creamy transitional milk contains higher levels of fat, lactose (milk sugar) and more calories than colostrum. During this time your breasts will become larger and firmer. Lactation is established and production of milk begins in the breast tissue. Transitional milk (about 600 to 700 ml per day) is produced from about day 5 to day 10-14.

Mature milk follows the transitional milk and begins to appear near the end of the second week after childbirth. This milk (about 700 to 900 ml per day) is thinner and contains more water than transitional milk. The composition remains more or less stable during this phase. There are two types of mature milk: foremilk and hindmilk. Foremilk occurs at the beginning of the feeding and contains water, vitamins and protein. Hindmilk comes at the end of the feeding when the breast is nearly empty and contains higher levels of fat.

Breast milk contains a variety of protective substances that increase your baby’s resistance to all sorts of infections. These substances are especially high in colostrum, but are also present in lower amounts in mature breast milk for months. The strongest protection against infection occurs in exclusively breastfed infants during the first several months of life, but continues throughout the duration of breastfeeding.

Human milk contains about 200 different oligosaccharides (HMO).These oligosaccharides provide the food for the good bacteria in the gut and help them grow and thrive. Gut health contributes to proper immune function because about 70% of the entire immune system is situated in the gut. 

At birth, your baby already has almost all of the brain cells they need for the rest of their life. Still, there is a lot of work in progress! In the first year of life, the size of your child's brain triples. Your baby needs specific nutrients for this rapid growth and to create connections between the brain cells. Breast milk provides fatty acids that are very important for the neurological development of your baby, including the long chain fatty acid docosahexaenoic acid (DHA). DHA is responsible for the growth, development, and maintenance of our brain. DHA is also a key component of the eye tissue. During the first two years of life, when your baby’s brain is growing rapidly, there is a crucial need for DHA. It is vital for the normal brain function that supports cognitive development; it enables thinking, learning and understanding throughout life.
 
The long chain fatty acid arachidonic acid (ARA) and the essential fatty acids alpha-linolenic acid (ALA) and linoleic acid (LA) play an important role in this. Breast milk provides all these important fatty acids although the level of DHA, particularly, depends on your diet.
 
When you are breastfeeding, the amount of DHA in your breast milk will depend on your diet; it is recommended that you consume 200 mg DHA daily. Eating two servings of oily fish (like salmon, sardines, herring or mackerel) a week can help you achieving this goal. Be careful not to eat more since these fish may contain pollutants that can build up in your body.

Protein is the major component of body cells and is essential for your baby’s growth. Breast milk contains two types of proteins: whey protein and casein. About 60% is whey protein, while 40% is casein. This balance allows for easy digestion. 

Breast milk is rich in nucleotides. Nucleotides are the building blocks for all cells in the body, and especially important for the cells of the intestinal tract (the gut) and the immune system. Nucleotides are vital components for the healthy growth and development of your baby.