Breast Milk Fat Separation – Why It Happens & What To Do About It

Breast milk is often referred to as liquid gold due to its myriad of health benefits for newborns. It is a complex and dynamic substance that provides essential nutrients, immune factors, and growth factors necessary for a baby’s development. One interesting characteristic of breast milk is its ability to separate into layers, with a distinct layer of fat rising to the top–similar to cow’s milk. In this article, we will delve into the science behind breast milk fat separation, exploring the factors influencing it and how to recombine it.

What Causes Breast Milk Fat Separation?

Breast milk separation occurs due to the phenomenon called creaming or cream-top separation. It’s a natural process driven by the differences in the densities of the milk components. The fat globules in breast milk are larger than other milk components and have a lower density. As a result, they tend to rise to the top, forming a distinct layer of cream. Many moms notice this breast milk fat separation in a pumped bottle of breast milk. The breast milk fat forms a “milk plug” at the top of the bottle.

how thick should layer of fat in breast milk be; breast milk fat separation

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Is My Breast Milk Still Good If It Separates?

Yes, your breast milk is perfectly fine if it separates into layers. Breast milk is a unique blend of proteins, carbohydrates, fats, vitamins, minerals, enzymes, and various bioactive components. The fat content of breast milk, mostly found in hindmilk, is crucial for a baby’s growth and brain development. It accounts for about 3-5% of the total volume of milk and is responsible for the milk’s energy density. As we mentioned above, these fat globules are heavier than other components of the milk which naturally causes breast milk fat separation.

Related article: Breast Milk Vs Cow Milk Taste – Are They Similar?

Factors Influencing Breast Milk Fat Separation

1. Time and Temperature

Given enough time, breast milk will naturally separate into layers. Higher temperatures can expedite the separation process, while lower temperatures may slow it down. Vigorous shaking or freezing and thawing breast milk can also affect fat separation. The below picture is of breast milk ice cubes. The white spots are frozen fat. You can see that the fat has separated away from the rest of the breast milk. This is totally fine and normal. When breast milk is warmed for a bottle, the fat will revert to its liquid form and will mix in with the rest of the milk.

breast milk fat separation

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2. Time of Day

The fat content of breast milk can vary from mother to mother and even within the same mother over the course of a feeding, the time of day, and throughout a mom’s breastfeeding journey. The fat content is typically higher in hindmilk (milk obtained later in a feeding) than in foremilk (milk obtained initially). As a feeding or pump session progresses, the hindmilk is released, resulting in higher fat content in the milk.

Some research suggests that the fat content tends to be higher in the milk produced during the later part of the day, such as the afternoon and evening. Milk supply tends to be lower in the later part of the day compared to the morning. Accordingly, it makes sense that when breast milk supply is lower, the available breast milk is fattier and more filling for a baby.

Related article: Drop in Milk Supply 4 Months & How to Fix It!

The below picture shows breast milk a mom pumped throughout a work day. You can see that while each bottle looks more or less the same, the colors and composition vary slightly for each bottle.

breast milk fat separation

How to Get Breast Milk Fat Off Bottles

Since fat is a stickier substance, breast milk fat separation can cause fat to stick to the sides of bottles. That fatty layer is rich in calories, essential fatty acids, and fat-soluble vitamins. You don’t want to leave any of it behind! In order to get the breast milk fat off bottles, you can try a few different methods we have outlined below.

Related article: Breasts Not Responding to Pump Anymore? Try This.

1. Gentle Swirling

Instead of shaking breast milk vigorously, gently swirling the container can help redistribute the fat back into the milk, ensuring a more consistent fat content throughout. See our article Shaking Breast Milk – Does It Really Damage It? if you have concerns about swirling or shaking breast milk.

shaking breast milk

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2. Running Under Warm Water

Placing the container of separated breast milk under warm water can help soften the fat globules and encourage their reintegration into the milk. Avoid using hot water, as it can potentially destroy some of the beneficial components of breast milk.

shaking breast milk; removing fat by running under water; breast milk fat separation

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3. Warming With Your Hands

In addition to the above methods, you can also try warming the breast milk with your hands. Breast milk fat will revert back to its liquid warm when warmed. By enclosing the bottle with your hands and gently swirling, the breast milk may slide off the bottle.

breast milk bottle in hands

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Breast milk fat separation is a natural occurrence influenced by various factors such as time, temperature, and fat content. The amount of fat in breast milk varies from mother to mother, but almost all moms who pump breast milk will experience breast milk fat separation. This separated milk is completely fine to give to your baby. Use a few of the above techniques to make sure you get all of the fat out of your pump bottles. You want your baby getting every ounce of milk you worked hard to pump!

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Shannon founded Work Breastfeed Mom in 2019 during her second round of pumping at work. She was tired of googling the same pumping questions over and over again, and discouraged at the lack of websites aimed at working breastfeeding moms. So, she created one herself. Shannon lives, works, and doles out Puffs to her little people in sunny Florida. She has her MBA and works as a strategic planner for a large healthcare system. She is passionate about coffee, memoirs, paddle boarding, and skincare routines. Shannon is mom to Scarlett and Ivy, and hopes to have more babies if her career allows.