What is foremilk and hindmilk?
The simple answer - it is all just milk! Your body doesn't make 2 kinds of milk. It just makes milk. There are no ducts which make and store skimmed milk while others store double cream, nor is there a switch that happens after feeding for a set length of time which suddenly taps into the hindmilk store and brings it online for your baby.
What happens is that as the milk sits in your breast, the fat globules stick together and stick to the walls of the alveoli and ducts. If you have seen expressed milk you may have noticed that as it sits it develops a fat layer at the top as the fat globules stick together. This is essentially what happens in the breast.
This means that when your baby begins to feed the first milk is higher in water and carbohydrate and lower in fat. This is as it should be. It is thirst quenching and all the carbohydrate is needed for the huge amount of brain development that is ongoing. Most women have a letdown within the first 1-2 minutes of a feed. During a letdown the ducts expand in diameter and muscle cells contract and squeeze milk (and the fat globules) down the ducts. This means that the fat starts to get pushed down (yes within the first minute or 2 of a feed!). As the feed continues the milk gets gradually and continually fattier and fattier as the fat is moved down. So there isn't a point where you suddenly tap into hind milk. There is no distinction - there is just milk.
That is not the whole story though. Fat content varies enormously through the day and from woman to woman. In the morning we tend to have higher volume of milk with less fat (that's why you feel fuller in the mornings) and in the evening we tend to have less volume (that's why you worry about not feeling full) but the milk is higher in fat. An emptier breast has higher fat content than a fuller breast (so babies who feed frequently get more fatty milk). Studies have suggested that women with baby boys tend to have more fat content than baby girls. Women who have been lactating for over a year tend to have more fat content that those who are newly lactating. Women who use massage during feeds or use breast compression have more fat content in the milk than those who don't.
Why does this foremilk/hindmilk thing matter?
For a mum with a full term healthy baby It shouldn't matter at all. Unfortunately it does matter because women worry about it and they change the way they breastfeed because of it. They often stay longer on one side to reach the hind milk. If we can get our heads out of the way and just relax into right brain breastfeeding, follow our baby's cues and breastfeed on demand then there is no need to worry about foremilk and hindmilk. It's doubtful that other mammals wonder about whether their baby is getting enough fat in the milk, and far fewer of them have issues with feeding their babies than humans do. If our baby is latching well, feeding effectively at the breast and we are feeding on cue then our milk will match baby's needs and our baby will create exactly the right fat content for him by how frequently and for how long he feeds. A baby is the only one who knows the composition of milk that he needs.
Given that the first letdown happens usually within a minute of a feed, you can see how we should be cautious about any advice to stay on one breast for [insert arbitrary number ] minutes in order to get the hind milk. Feeds shouldn't be timed. It doesn't make sense. We have to get away from this idea of our breasts and babies as uniform units who all create and drink similar volumes in a similar amount of time. We are individuals and so are our babies. Each woman stores different amounts of milk in her breasts with an individual fat composition, and our babies have an individually shaped and sized mouth, individual muscles and create individual vacuum. One baby may take what he needs in 10 minutes and another may take 40 minutes . The time isn't important. What is important is that the baby is drinking well (not just sucking) when he is at the breast. You don't need to spend 40 mins on one breast to get hindmilk if your baby drank well and cued that he was ready to swap sides earlier.
There aren't many breastfeeding rules that fit across all women - but one of them is this: Switching sides more frequently will stimulate more milk production. Staying on one breast and avoiding switching will lower production. Too many mums in the early weeks stick to one breast for long periods aiming to get the hind milk, only to find that their baby has low weight. Ironically many of these mums are trying to get the hind milk because they believe it will help with weight gain. If you have found yourself in this situation contact an IBCLC (International Board Certified Lactation Consultant) or an accredited Breastfeeding Counsellor. Changing the feeding pattern can get things back on track quickly with the right support. In most cases switching more frequently increases milk supply. The larger supply and increased amount of milk taken in by the baby then increases weight gain.
The first 5 weeks are crucial for stimulating milk production, and a mum changes from producing teaspoons of colostrum after birth to producing anywhere between 25-35 Oz a day in a few short weeks. It's an enormous change and your breasts need lots of stimulation to meet that demand. Sticking to one side for too long risks lowering your chances of exclusively feeding your baby.
It is the volume of milk that a breastfed baby drinks which is linked
with growth - not the amount of fat.
with growth - not the amount of fat.
Don't be afraid to swap sides with your newborn. If you find that you have too much milk later it is easily resolved, but building your supply after the first few weeks is harder. Effective feeding and a good intake of milk volume is what is important for weight gain, not how much fat a baby gets in one particular feed. Watch your baby during a feed, not the clock.
A great blog looking at how milk changes through the course of a feed, complete with photos ever couple of minutes during the feed: http://thefunnyshapedwoman.blogspot.co.uk/2011/05/foremilk-and-hindmilk-in-quest-of.html
General info on foremilk/hind milk - http://www.nancymohrbacher.com/blog/2010/6/27/worries-about-foremilk-and-hindmilk.html
Article on how milk fat content changes in human milk - http://kellymom.com/nutrition/milk/change-milkfat/
How fat content is tailored to gender and circumstance - http://www.scientificamerican.com/article/boys-and-girls-may-get-different-breast-milk/
Is My Baby Getting Enough Milk (Jack Newman) - http://www.breastfeedinginc.ca/content.php?pagename=doc-IMB