You may notice your milk seems thicker and creamier towards the end of a feed. This is because, as the feed progresses, the fat composition gradually increases due to the mechanics of milk moving through the breast. It's often referred to as hindmilk, while the first more 'watery' milk is known as foremilk.
The fuller the breast, the lower the fat content of the milk. Therefore, milk that is expressed at the beginning of a nursing or pumping session tends to be more watery than milk expressed at the end. (However, if sessions occur close together – and the breast doesn't have time to refill – this may not always be true.)
The longer the time between feeds, the more diluted the leftover milk becomes. This 'watery' milk has a higher lactose content and less fat than the milk stored in the milk-making cells higher up in your breast. You can't tell how much fat your baby has received from the length of a feed.
Breastmilk at night
For most mothers, breastmilk will gradually increase in fat content throughout the day. During the evening, young babies often cluster feed, taking in frequent feeds of this fattier milk, which tends to satisfy them enough to have their longest stretch of sleep.
How long should a baby nurse to get hindmilk? After about 10 to 15 minutes of breastfeeding, the milk flow slows and transitions to the sweet and creamy hindmilk, which contains vitamins A and E, and has more fat and calories than foremilk.
Usually blueish or clear, watery breast milk is indicative of “foremilk.” Foremilk is the first milk that flows at the start of a pumping (or nursing) session and is thinner and lower in fat than the creamier, whiter milk you see at the end of a session.
The sheer volume of milk and high sugar content often means babies gain weight very well with foremilk hindmilk imbalance—even though they aren't getting their “pudding”. However occasionally some babies may not gain enough weight in this situation.
Go for non-fat or low-fat milk, yogurt, and cheese. If you're breastfeeding, you need at least 4 servings of dairy each day. Choose unsaturated fats and oils — and stay away from trans fat. Read food labels to see what's inside.
"Sometimes, it takes on the appearance of skim milk. However, it's important to note that while mature milk is typically white, it can change colors depending on your diet and from the foods you eat. Frozen breast milk may appear yellow since it separates and can even look layered."
Breast fed babies can be given an alginate thickener before feeds, and bottle feeds can be thickened with a preparation based on rice starch, corn starch, locust bean gum or carob bean gum.
The overall amount of fat in breast milk is highest in the evening and at night, compared with milk produced during the day. However, multiple factors contribute to the amount of fat in breast milk, especially the frequency of feeding.
Fat content increases gradually as the breast becomes emptier, as fat globules are “forced” out of the breast by successive milk ejections. A longer feed interval means lower initial fat content at the start of the next feed, because fat adheres to the alveoli/ducts while milk stands in the breast between feeds.
The composition of breast milk changes across the day, giving energising morning milk a different cocktail of ingredients than soothing evening milk. Researchers believe this 'chrononutrition' may help program infants' emerging circadian biology, the internal timekeeper that allows babies to distinguish day from night.
Day milk, by contrast, has more activity-promoting amino acids than night milk. Iron in milk peaks at around noon; vitamin E peaks in the evening. Minerals like magnesium, zinc, potassium and sodium are all highest in the morning. Daytime milk may pack a special immune punch.
Breast milk tends to be extra watery first thing in the morning because milk has been sitting in your breasts for awhile as you and your baby sleep at night.
As more milk is continuously being produced, the longer you go in between feedings, the more of that watery foremilk builds up. Going several hours in between nursing sessions means your baby might get more of that foremilk.
Breast milk pumped at night has more melatonin — the hormone of drowsiness — and higher levels of nucleotides thought to promote sleep. By contrast, breast milk pumped in the morning features higher concentration of cortisol, a stress hormone that makes babies more alert.
If this is something that you're concerned about, my suggestion is to test this out with your baby and see how it goes. Give morning milk in the morning and night milk at night for a few days, and then switch for a few days. While you're doing this, pay attention to your baby.