Do you know what is in your breastmilk?
Here we run through some common questions and nutritional facts about breast milk that you might not already know, starting off with the most simple - what exactly is breast milk?
Did you know that there are different types of breast milk? If you've never heard of fore-milk or hind-milk, or perhaps never understood the difference, find out here. And if you're really curious, you can even look up what your breast milk tastes like, and how what you eat can change the flavour. Breast milk also changes over time, and your breast milk can be very different to your friend's breastmilk.
Breast milk contains a perfect balance of fats, proteins, carbohydrates, vitamins and minerals to nourish your baby in the early weeks and months. Each of these components has a specific role in nourishing a baby.
Breast milk's essential fats
The essential fats in breast milk is the primary calorie source for your baby’s growth and development. They are vital for your baby’s brain development and also help your baby’s body absorb fat-soluble vitamins.
Studies have found that children with diets high in omega-3 fats (think oily fish, nuts and seeds) and low in omega-6 fats (that come from vegetable oils such as corn and soybean) score markedly higher on international tests. More specifically, the amount of omega-3 docosahexaenoic acid (DHA) in a mother’s milk is one of the strongest predictors of test performance. The omega-3 to omega-6 ratio should be about 1:5 for optimal health.
Further studies indicate that omega-3 fatty acids may be valuable in an unborn baby’s development, finding if pregnant women consumed DHA it resulted in improved brain development in their babies.
Carbohydrates in breast milk
Carbohydrates are an essential component of breast milk, with lactose making up around 40 percent of the total calories. The lactose in breast milk not only helps decrease bad bacteria in the baby’s stomach, it also improves the absorption of minerals such as magnesium, calcium and phosphorus. Breast milk also contains Leukocytes, living cells that help fight infection and are only found in breast milk.
The range of vitamins available to your baby in breast milk depends on your diet during pregnancy and breastfeeding – the better quality your diet, the greater range of nutrients available to your baby. So long as you’re eating a nutritionally well-balanced diet your breast milk will contain the nutrients your baby requires. However, to ensure that your baby receives the complete range of the nutrients they need, taking a tailored pregnancy and breastfeeding vitamin is recommended. Essential vitamins for breastfeeding include vitamins A, D, E, K and C. Along with riboflavin, niacin and pantothenic acid.
Breast milk is primarily made up of two types of proteins: whey and casein. Whey protein is easier for the baby to digest, which is why breast milk is always made up of 60 – 80 percent whey protein. Both of these proteins have infection-fighting properties, but breast milk is also packed with immunoproteins, each with specific nutritional properties.
These immunoproteins in breast milk are:
- Bifidus factor which supports the growth of lactobacillus, a beneficial bacteria.
- Lactoferrin to inhibit harmful, iron-dependent organisms in the gastrointestinal tract.
- Lysozyme to protect against salmonella and E. Coli.
- Secretory IgA which has a range of beneficial properties and helps protect babies from a wide range of bacteria and viruses.
The composition of breast milk can change over the course of a feed depending on the time between feeds and how empty the breast was at the last feed. Generally speaking, at the start of a feed your baby will consume fore-milk. As the feed progresses the composition of the milk tends to change and becomes richer, and more nutrient-dense.
What is fore-milk? Fore-milk is a light, lactose and vitamin-rich milk which is available to a baby at the start of a breastfeed and designed to satisgy his thirst.
What is hind-milk? When milk is produced, fat sticks to the milk ducts and is slowly released over the course of breastfeeding. This richer, creamier, more fat-dense milk is called the hind-milk. There is no need to worry about whether your baby is receiving the correct balance of fore-milk and hind-milk.
If your baby drains one breast before starting on the next you can be sure that he is getting a good balance of fore-milk and hind-milk.
While the taste varies from woman to woman, depending on the time of the day and what they’ve eaten, the general consensus is that breast milk tastes sweet and a little nutty, with an almost vanilla-like flavour.
Depending on the time of day, the flavour of breast milk will also change as the fat composition varies depending on how long it’s been between feeds and how empty the breast is at the end of a feed.
Fore-milk is much more watery, and lighter in taste than the creamy hind-milk – which can almost have the consistency and flavour of condensed milk.
Just like asparagus affects the scent of urine, strong-flavoured foods such as broccoli can also influence the flavour of your breast milk. If you notice your baby fussing during a particular feed, have a think about what you’ve eaten that day – was it particularly garlic-laden or rich? It normally takes between two and six hours for food to affect breast milk so if you notice baby fussing after you’ve eaten a certain food, it’s best to abstain if you know you’ll be feeding within this time frame.
Human breast milk is essentially the same in every woman. All breast milk is formulated by a woman’s body to nourish her baby – but there are a number of factors that influence the make up of breast milk:
- A woman’s diet: during pregnancy and breastfeeding your breast milk stores nutrients to help nourish your baby. Women who are malnourished are not capable of providing the nutrients vital for baby’s growth and development.
- How often and how long a baby feeds: the amount of time a baby feeds, and how often they feed, will influence the fat component in a mother’s breast milk. If a baby feeds and drains the breast, then the next feed will contain more fat because as the breast fills, the fat stores clinging to the sides of the breast will be incorporated with the milk.
- The baby’s age: as your baby develops his feeding will change. He’ll feed less often and this will affect the composition of the breast milk. Once your baby starts eating solids he’ll need less calories from breast milk, and the composition will change again as he will feed less often.
- The amount of exercise a mother does: if you exercise a lot it will make a difference to your breast milk. Generally speaking, you can continue to exercise at a similar level to when you were first pregnant, but it’s best to increase exercise levels slowly. If you’re getting enough sleep and rest, then up to an hour a day of exercise won’t be an issue.
- The amount of fluid a woman drinks: drinking sufficient water, eight glasses a day, or around 1.5 to 2 litres, will help ensure a healthy breast milk supply. You won’t increase your breast milk supply by drinking more water – but being well hydrated is essential for a healthy breast milk supply. Drinking a moderate amount of caffeine won’t be a problem for your baby, but more than a few cups a day could be an issue.
Breast milk undergoes a range of changes. It changes from morning to night, from feed-to-feed, and over the months as your baby grows and develops . Breast milk is quite remarkable as it will adapt to your baby’s needs – but the amount of breast milk each mother produces will generally stay around the same. Human breast milk contains an average of between 270 and 315 kilojoules per 100ml – with this amount varying due to the change in fat content .
The fat content of breast milk will vary according to how empty the breast is: an empty breast means more fat, a full breast means less fat . A woman’s body will continue to produce breast milk as long as she feeds her baby. The combination of the two main hormones needed to produce milk – prolactin and oxytocin – will ensure that so long as a baby suckles at the breast, milk will be produced .
In early 2014 Harvard University researcher Katie Hinde released the results of her study into variations in the composition of breast milk produced for male and female offspring in rhesus monkeys. She found that milk is richer in fat when monkeys have male babies, and that volume is increased when the offspring is female. From these results she hypothesised that donor milk for those vulnerable babies who need donated breast milk should perhaps be gender matched to ensure the most appropriate nutrition.
In August 2013 Swiss researchers published a study in the journal Environmental Microbiology, which found that the gut flora which prevents intestinal disorders and promotes good digestive health travels from the mother’s gut via her breast milk and into the baby’s digestive system. 
The researchers found the same strains of several types of beneficial bacteria in breast milk and in mothers’ and babies’ faeces.
The study’s summary describes this transfer of bacteria as “a novel way of mother–neonate communication, in which maternal gut bacteria reach breast milk via an entero-mammary pathway to influence neonatal gut colonisation and maturation of the immune system.”
Furthermore, the particular sugars found in breast milk also work to selectively nourish the gut bacteria infants need. Eric Rogier from the University of Kentucky has found a milk antibody called SIgA also helps to set up the right community of gut microbes. Without it, young mice face long-lasting consequences, including several signs of inflammatory bowel diseases (IBD). “This antibody sets up a healthier environment in an infant’s intestinal tract, so they’re better prepared to withstand environmental problems later in life,” says Charlotte Kaetzel, who led the study.
Stem cells were first identified in breast milk in 2007, but it wasn’t until 2014 that scientists were able to show that these actually performed a useful function, rather than simply leaking unavoidably into breast milk.
Findings presented at the National Breastfeeding and Lactation Symposium in London in October 2014, suggest that the stem cells in breast milk actually play a part in the development of a number of organs, including the brain, pancreas, liver, spleen and kidneys. Many of the stem cells were found to integrate into the body and become functional cells.
These findings, as well as demonstrating the role these cells play in a baby’s development, also suggest that the breast milk stem cells could be useful in therapeutic applications.
This article was written by Linda Drummond and adapted for Kidspot, New Zealand's leading parenting and pregnancy resource.
Breastfeeding is best for babies and provides many benefits. Combined breast and bottle feeding in the first weeks of life may reduce the supply of your own breast milk. Always consult your doctor, midwife or health care professional for advice about feeding your baby. This post is part of the Early Life Nutrition story.