There is a common misconception that we make two different types of milk: ‘foremilk’ and ‘hindmilk’. You might have heard that foremilk is watery, thin and low in fat, and that hindmilk is rich, creamy, and high in fat. That’s not how it works. We produce just one type of milk, all of which is relatively high in fat and all of which contains essential nutrients for our babies. ‘foremilk’ just refers to the milk that comes out right at the beginning of a feed, and ‘hindmilk’ just refers to the milk that comes out right at the end of a feed. The hindmilk of a feed usually does have a slightly higher fat content than the foremilk of that particular feed, but the foremilk of the next feed might have a higher fat content than the hindmilk of the previous feed. Here’s how it works:
How the fat composition of your milk changes throughout each feed
When milk is produced and stored in your breasts between feeds, some of the fat globules stick to each other and separate from the rest of the milk, sticking to the walls of your milk ducts. When your let down reflex is triggered at the beginning of a feed, the milk leaves some of its fat behind when it comes out. As the feed progresses, more and more of the fat left behind is washed from the walls of your milk ducts, so the fat content of your milk becomes gradually higher. The change in fat composition is very gradual. This is one of the reasons why it is best for your baby to be the one to decide how long their feeds last, and allow them to come off the first breast by themselves before you offer the second, because they will then get all the fat they need. However, this does NOT mean that foremilk is always low in fat.
Both of the bottles in the picture above contain milk expressed just before a feed. They therefore both contain foremilk. However, the bottle on the right was expressed when my breasts were very full, and the bottle on the left was expressed when my breasts were not as full. It is the degree of fullness of the breasts which determines the fat content of the foremilk of each feed.
When it has been a several hours since your baby’s last feed, more of the fat will have separated from the milk stored in your breasts, so the milk which comes out at the very beginning will be relatively lower in fat than the milk which comes out at the end. When it hasn’t been so long since your last feed, less of the fat will have separated, so the milk which comes out at the begining won’t be much lower than the milk which comes out at the end, and may have a higher fat content than the milk which came out at the end of the previous feed!
IBCLC Kelly Bonyata has a brilliant analogy for this:
‘think of the beginning of a nursing session as being like turning on a hot water faucet.The first water you get out of the tap isn’t usually hot, but cold. As the water runs, it gradually gets warmer and warmer and warmer. This is what happens with the fat content in mom’s milk – moms’s milk gradually increases in fat content until the end of the feeding. If there is a long period of time before the faucet is used again, then you go through the “cold to hot” process once more, but if you turn the water on fairly soon after it was used then the water is either pretty warm or still hot, depending upon how long it’s been since the faucet was last on.This is how it works with mother’s milk too – the longer the time between feedings, the lower the fat content at the beginning of the next feeding. If feedings are closer together, you’re starting off with a higher fat content.’
There is no need to worry about how much foremilk/hindmilk your baby is getting!
Is my milk fatty enough?
Back in the 50’s, women were being told everyday that their milk isn’t fatty enough. We now know that it is not the fat content of milk which determines a baby’s weight gain, but the overall volume of milk they are consuming. Milk not being fatty enough isn’t a thing. If you have been told that your milk isn’t fatty enough, get in touch with a Breastfeeding Counsellor or IBCLC. Weight issues are usually caused by baby not getting enough milk, rather than not getting enough fat. There can be certain situations where a baby really isn’t getting enough fat from Mum’s milk, but this is not because her milk does not contain enough fat, and there are things that can be done about it.
Lactose overload is caused when a baby is getting plenty of milk, but they are not getting enough fat. Some people call this ‘formilk/hindmilk imbalance’ but, as explained above, this term is innacurate and confusing. Breastmilk is high in lactose, and the fat in breastmilk helps to slow down digestion so that your baby’s body has enough time to properly digest the lactose. When baby isn’t getting enough fat, the milk can pass through baby’s body faster than the lactose can be broken down, which leads to it fermenting within the gut causing symptoms such as green, frothy stools, flatulence, and pain along with rapid weight gain. This is often misdiagnosed as lactose intolerance (which is very rare in breastfed babies) or an allergy, which can lead to mothers stopping breastfeeding early. In most cases, however, lactose overload is caused by baby not feeding effectively, baby being limited to a certain amount of time at each breast, or mum having an oversupply of milk, and can be solved with the right support. If you think your baby might be experiencing lactose overload, speak to your GP or Midwife and find some specialist breastfeeding support here.
Mohrbacher, N. Breastfeeding Answers Made Simple: A Guide for Helping Mothers, 2010
Kent, J. C. (2007). How Breastfeeding Works, Journal of midwifery & women’s health, 52(6), 564-570
Hartmann P. E, Di Rosio A, Owens R. A, Daly S. E (1993) Degree of breast emptying explains changes in the fat content, but not fatty acid composition, of human milk, Experimental Physiology: Translation and Integration 78 (6), 741-755, 1993