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Breastmilk composition

Breastmilk composition


Breastmilk has all the nutrients and bioactive factors needed for optimal infant health and development. The composition of breastmilk varies during the different stages of lactation and between term or preterm babies.

While studies into breastmilk composition are still ongoing, here are some of the most commonly recognised components of breastmilk:

  • 700+ types of proteins
  • 40+ types of enzymes which aid in digestion and nutrient absorption
  • 200 + types of oligosaccharides (complex sugars) which act as probiotics and protect your baby’s gut from infections
  • Live cells – stem cells to repair organ damage, white cells to prevent infection
  • Hormones – regulates baby’s appetite, sleep and bonding
  • Vitamins and Minerals – supports growth, healthy teeth & strong bones
  • Growth factors – supports healthy organ development
  • Immunoglobulins (antibodies) – protecting your baby from infections and illnesses
  • Long-chain fatty acids – building blocks in nervous system, brain and eye development

Days 1-4 - Composition of Colostrum

There’s a reason everyone calls Colostrum ‘liquid gold’!

Colostrum contains similar components of mature breastmilk, however in varied quantities specifically tailored to your baby’s needs. Colostrum protects your baby from infections with countless antibodies, stem cells and white cells.

Colostrum contains growth and protective proteins which help to colonize and line the susceptible digestive tract following birth. Colostrum is very easy for your baby to digest. It acts as a laxative to help pass meconium and prevent jaundice.

2-4 Weeks – Composition of Transitional Breastmilk

As your breastmilk ‘comes in’ and your breasts feel fuller, the quantity of breastmilk increases.

Transitional breastmilk has higher levels of fats, carbohydrates, calories and lactose. This is ideal for your rapidly growing newborn.

4+ Weeks – Mature Milk

Fully mature breastmilk is rich in proteins, sugars, vitamins, minerals and hormones needed for healthy development. Transient changes will occur in your breastmilk to suit your baby’s individual needs.

Written by Keryn Thompson, RM & IBCLC (L-301766)


Alderete, T., Autran, C., Brekke, B., Knight, R., Bode, L., Goran, M. and Fields, D., 2015. Associations between human milk oligosaccharides and infant body composition in the first 6 mo of life. The American Journal of Clinical Nutrition, 102(6), pp.1381-1388.

Gila-Diaz, A., Arribas, S., Algara, A., Martín-Cabrejas, M., López de Pablo, Á., Sáenz de Pipaón, M. and Ramiro-Cortijo, D., 2019. A Review of Bioactive Factors in Human Breastmilk: A Focus on Prematurity. Nutrients, 11(6), p.1307.

Grönlund, M., Gueimonde, M., Laitinen, K., Kociubinski, G., Grönroos, T., Salminen, S. and Isolauri, E., 2007. Maternal breast-milk and intestinal bifidobacteria guide the compositional development of the Bifidobacterium microbiota in infants at risk of allergic disease. Clinical & Experimental Allergy, 37(12), pp.1764-1772.

Scherbaum, V. and Srour, M., 2016. The Role of Breastfeeding in the Prevention of Childhood Malnutrition. World Review of Nutrition and Dietetics, pp.82-97.

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