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Imagine you could get all your nutrition from one liquid, which had the perfect nutrition for you1 and also had other benefits like helping your immune system and development!
Your baby has this opportunity, with your breast milk – so what is in this magic liquid that makes it so special?
Breastmilk provides all the nutrients a baby needs in the first 6 months of life, in fact evidence suggests that our ancestors breastfed their babies up to 6 years of age2.
Breast milk contains 100s of different types of human milk oligosaccharides structures that work together to help your baby develop a healthy immune system through the gut3.
Your breast milk contains immune cells, which are called leukocytes, will increase in number if you or your baby are ill to protect your baby from infection4.
Breast milk is an extremely complex liquid, which has more components than could ever be listed on a page. It constantly changes and therefore is difficult to discover the exact contents of and we are discovering new components of it constantly. It varies in composition from mother to mother, due to your genes, diet, lifestyle, health and lactational stage, and will provide complete nutrition to your baby8. There are millions of different components in breast milk, including different types of proteins, carbohydrates, minerals, vitamins and many other components, which are unique and tailored to you baby.
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What’s in breast milk?
Your breast milk is 87.5% water5. The rest contains millions of different components, including various carbohydrates, fats, proteins and minerals. During a feed, breast milk changes colour and becomes thicker as the amount of energy it contains gradually increases6.
Breastmilk gives complete nutrition
Breast milk constant adapts to meet the needs of your baby, changing during the time of day, age of your baby and even during one feed itself! During a feed your milk will change from for foremilk to hindmilk.
‘Foremilk’ – the first milk of a breastfeeding session is packed with all the carbohydrates, protein and vitamins a baby needs. As a result of its high water composition, it also protects exclusively breastfed babies from dehydration 6,7.
The ‘hindmilk’ produced towards the end of a breastfeeding session looks thicker and is darker in colour. This is because its energy and fat content increases as the feed goes on, allowing babies to take on enough energy to go longer between feeds 6,7.
The energy in breast milk comes from fat and protein, and this gives breast milk its calorific energy content.
So how many calories are there in breast milk?
There are approximately 67 calories per 100ml of breast milk, but this will constantly adapt to change to your baby’s needs8.
Breast milk composition
Carbohydrates in breast milk
The main carbohydrate in breast milk is lactose8. Lactose, along with other carbohydrates in breast milk, provides a large amount of the energy content of breast milk to allow all the normal process in the body to occur. Lactose also helps with mineral absorption9 and help your baby to absorb more calcium from your breast milk. Lactose also helps the ‘good bacteria’ in your baby’s gut10, as any lactose which isn’t digested in your baby’s stomach will be fermented by the ‘good’ bacteria in your baby’s gut.
The fat content of breast milk
Breast milk contains many different types of fats11, which all have different important roles in your baby’s development. Long chain polyunsaturated fatty acids, or LCPs, for example, are important for the development of your baby’s brain. Research has shown that two particularly important LCPs – AA and DHA – are found in breast milk12. Consuming more of the important fats during pregnancy and while breastfeeding can help your baby’s development, encouraging better visual and brain development and movement skills13. The main ways to include LCPs in your diet are by eating fish, eggs and meat in your healthy breastfeeding diet.
Protein in breast milk
Protein is really important for your baby as they develop. Protein provides the basic building blocks (amino acids) for the growth and repair of all the cells in your baby’s body14. Protein in breast milk is in the form of whey and casein. There are also many proteins in breast milk, which have very specific and important jobs15. For example, your breast milk contains an enormous amount of antibodies that help to support your baby’s immune system, and therefore help your baby’s ability to fight off the infections16.
Human milk oligosaccharides (HMOs) are carbohydrate molecules that naturally occur in breast milk. On average, they are the third largest solid component in breast milk behind lactose and lipids3 with each litre of breast milk contains approximately 12–15g of HMOs17, as with all factors in breast milk these levels are very different between mothers due to the unique nature of your own breastmilk. Breast milk has around 200 known HMO structures that work together to help your baby develop a healthy immune system through the gut3.
Vitamins and Minerals
Breast milk contains many different types of vitamins and minerals18, for example vitamins A, B6, D and iodine to name just a few. It is important that you make sure you have a healthy balanced diet throughout pregnancy and breastfeeding, as these vitamins and minerals come from your stores19. All these vitamins and minerals have roles within the body from vitamin E’s role in immune system stimulation to iodine’s role in growth and mental development20.
Breast milk contains millions of other factors which help your baby from helping their immune system to developmental benefits. For example, breast milk contains stem cells, growth factors, postbiotics, bacteria, immune factors (cytokines), nucleotides, hormones and immune cells8,20,21.
Breast milk is rich in nucleotides, which are the building blocks for all cells in the body, including the immune system. Research has shown that nucleotides support the activity of certain cells within the immune system, helping protect the body against infection22.
Hormones found in breast milk change throughout the day, and this helps to regulate the baby’s body functions, such as energy balance and sleep23.
Immune cells help to protect your baby while their own immune system is learning how to work best. These cells, which are called leukocytes, will increase in number if you or your baby are ill to protect your baby from infection7.
Dr Bernd Stahl
Dr Bernd Stahl is an expert in breastfeeding and breast milk, and is currently the Director of Human Milk Research & Analytical Science at Danone Nutricia Research. For over 25 years, he has contributed significantly to the understanding of the benefits of breast milk and its impact on early life.
- Agostoni, C., et al. J Pediatr Gastroenterol Nutr, 2009;49(1):112-125.
- G.E Kennedy – From the ape’s dilemma to the weanling’s dilemma: early weaning and its evolutionary context.
- Ruhaak LR and Lebrilla CB. Adv Nutr 2012; 3:406S-414S.
- Hassiotou F et al. Clin Transl Immunology. 2013;2(4):e3.
- Martin, C., Ling, P. and Blackburn, G. Nutrients, 2016;8(5):279.
- Hartmann PE. Mammary gland: Past, present, and future. In: Hale & Hartmann’s Textbook of Human Lactation. Amarillo, TX: Hale Publishing, 2007:3-16.
- Mizuno et al. Int Breastfeed J 2009;4(1):7.
- Ballard, O., & Morrow, A. L. Pediatr. Clin. North Am., 2013;60(1), 49–74.
- Ziegler, E. and Fomon, S. J. Pediatr. Gastroenterol. Nutr., 1983;2(2):288-294.
- Forsgård, R. Am. J. Clin. Nutr., 2019;110(2):273-279.
- Zou, X., et al.. J Agr Food Chem, 2012;60(29):7158-7167
- Jensen RG. Handbook of milk composition. London Academic Press 1995.
- European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion: DHA and ARA and visual development. EFSA Journal 2009;941:1-14.
- Wu, G. F Adv Nutr, 2010;1(1):31-37.
- Molinari, C. et al. J. Proteome Res., 2012;11(3):1696-1714
- Cabinian A et al. PLoS One. 2016;11(6):e0156762.
- \Thurl S, et al. Nutr Rev, 2017;75(11):920-33.
- LASER Analytica, 2014. Comprehensive literature search and review of breast milk composition as preparatory work for the setting of dietary reference values for vitamins and minerals. EFSA supporting publication 2014:EN-629, 154 1
- Y. de Vries, et al. Nutrients, 2018;10(6):687.
- Bergmann H, et al. Br J Nutr, 2014;112(7):1119-28.
- Hunt KM, et al. PLoS One,2011;6(6):e21313.
- Carver, J. Acta Paediatrica,1999;88:83-88.
- White, R. Breastfeed Med, 2017;12(7)398-400.
Questions about feeding and nutrition?
Our midwives, nutritionists and feeding advisors are always on hand to talk about feeding your baby. So if you have a question, just get in touch.