Breast milk is widely known as a superfood that contains all the nutrients and antibodies your baby needs to grow and thrive. It’s not called liquid gold for nothing!
That’s why it’s so hard for some parents to throw away leftover milk when the baby doesn’t drink it all, and there comes the question of “can you reheat breast milk twice?” If you can reheat it, how many times can it be done?
There’s a lot of information about the benefits of breastfeeding, how to pump and express breast milk and how to safely store it. There are guidelines about how much time breast milk can last depending on the temperature you keep them.
And there are instructions about how to use previously stored breast milk and how to warm it and feed it to your baby. But regarding reheating breast milk and if it’s safe or not, there is contradicting information because there’s not enough scientific evidence to back up the claims.
Here’s what we’ve found so far.
Storing breast milk
For many reasons, a breastfeeding mother can decide to store breast milk, and this practice is safe as long as you follow the proper guidelines to ensure that the quality of the breast milk is not affected.
For example, if breast milk is going to be stored and not used within the next 4 hours, it should be immediately refrigerated or directly frozen, so there’s no bacterial growth that impairs the quality of the breast milk. Also, high temperatures can spoil breast milk, and the best way to avoid this is to store it at an adequate temperature.
- Freshly expressed or pumped milk:
- Room temperature (77°F / 25°C): Up to 4 hours
- Refrigerated (40°F / 4°C): Up to 4-6 days
- Frozen (0°F / -18°C): Within 6 months (best) or 12 months (acceptable)
- Thawed breast milk (previously frozen):
- Room temperature (77°F / 25°C): Up to 1 – 2 hours
- Refrigerated (40°F / 4°C): Up to 24 hours
- Frozen (0°F / -18°C): Thawed breast milk should not be refrozen.
- Leftover breast milk from a feeding:
- It should be used within 2 hours after the baby finished feeding.
It’s also recommended that you store breast milk in small amounts or those corresponding to a single feeding session, so you are sure that once you thaw it (in the case of frozen breast milk) or warm it, your baby will consume it all and there will be no leftover milk.
Expressed breast milk should be stored in food-grade containers or specifically designed milk storage bags. If you’re freezing it, you need to leave enough space to allow the milk to expand when frozen and avoid spillage or that the pressure opens the container, and the milk gets contaminated.
To thaw breast milk, you can use bottle warmers, a pot with warm water, or running warm or lukewarm water to slowly defrost the milk without damaging it. You can also place it in the refrigerator to thaw more slowly. What must be avoided at all costs is overheating it with boiling water or using the microwave because too high temperatures make the breast milk lose its nutritional value and create hot spots that may burn the baby’s mouth.
But before you store breast milk, you have to make sure that your breast pump and all its components are cleaned and sterilized to avoid bacterial contamination on the breast milk before you pump milk. Same with the storage containers you select and the bottle of breast milk you use to feed your baby.
Follow these guidelines to ensure you store your freshly expressed milk in optimum conditions to be used later. Skipping any steps may cause your breast milk to lose its benefits and even spoilt.
What happens when you heat breast milk?
Did you know you don’t need to warm breast milk to feed your baby? Heating breast milk is a matter of preference, and it’s safe to provide cold breast milk to your little ones if they don’t mind. What you can’t do is feed them frozen milk, but at room temperature or cold from the refrigerator causes no harm.
It’s important to understand that once breast milk is expressed or pumped from the body, it begins a natural process of degrading, which can be slowed with temperature. And that’s why the lower the temperature, the longer it can be stored.
Once you thaw frozen breast milk, this degrading process restarts, and bacteria begin to grow. The initial bacterial load in the breast milk before it was stored is something else to keep in mind.
So if you heat breast milk, bacteria will grow faster. And regarding partially consumed breast milk, when babies feed, saliva comes in contact with the breast milk, so, although it may be good bacteria in the baby’s saliva, it will contaminate the milk.
Can you reheat breastmilk twice?
Here’s where the answer varies. The CDC doesn’t recommend reheating breast milk and states that it must be consumed within 2 hours of being left out.
But many mothers have admitted a resistance to throwing out the precious liquid gold and that they’ve stored the remaining milk for later feedings.
There are clear signs that you can use as a reference to see if breast milk has gone bad. Spoiled milk smells, looks, and tastes different. And this applies to baby formulas as well.
Spoiled breast milk has a distinctive strong smell. Some may call it foul but don’t confuse it with the soapy smell of high lipase in breast milk. The baby may reject milk with a high lipase content, but this is not harmful to them, while spoiled breastmilk is.
Also, milk that has gone bad tastes sour, so if you want to make sure it’s safe for your baby to consume it, taste it beforehand. Finally, when frozen or cooled, breast milk tends to separate, and you will notice a fat layer on top. If it’s not spoilt, you will be able to mix it back together by swirling or shaking it; but if it’s not mixing back and you notice chunks, or it looks curdled, you need to throw it away.
All these visual cues may help determine if it’s safe to give the milk to the baby after it’s been reheated, but what you won’t be able to see is if the essential nutrients remain active or if harmful bacteria are growing in the unused breast milk.
For that reason, under no circumstances should you give reheated breast milk to premature, sensitive babies or those with a compromised immune system. This is a risk that you should avoid at all costs and may cause serious harm to the baby’s health.
Can warmed breast milk be refrigerated again?
Again, there’s not enough evidence to back up a recommendation to refrigerate breast milk previously warmed to prevent or slow down bacterial growth. But it makes sense that if you decide to reheat breast milk, despite the CDC’s recommendations of using it within 2 hours, you store it in the refrigerator rather than at ambient temperature.
A refrigerator is a more controlled environment and a steady temperature that will not be achieved sitting at room temperature.
According to the Academy of breastfeeding medicine, there’s little information about the effects of refreezing thawed human milk. The bacterial growth and the loss of antibacterial activity in thawed milk will depend on the thawing method and the initial bacterial presence in the milk.
What to keep in mind when using reheated breast milk
As we’ve said before, this is a practice that’s not recommended by the CDC, the Academy of Breastfeeding Medicine, and other specialists, but if you decide to do it, keep the following pointers in mind to keep a healthy baby.
- Properly handling breast milk is key to ensuring its storage and quality. Follow the storage guidelines above or read the CDC’s recommendations to ensure your breast milk will not lose its nutritional value.
- Proper storage of pumped milk includes understanding the temperatures and time frames to avoid human milk from spoiling or losing nutritional value.
- It’s better to store the exact amount of breast milk the baby drinks in one sitting to avoid leftovers.
- There’re different warming methods to heat and reheat breast milk, such as a bottle warmer, running hot water, and a bowl of warm water, among others. But overheating the breast milk or using the microwave should be avoided to prevent damaging the breast milk and burning the baby’s mouth.
- Said warming techniques can be used to thaw your currently available storage, but you can also place it in the refrigerator overnight and achieve the same result with less risk of high temperatures breaking down the breast milk’s nutrients.
- The recommended breast milk warming temperatures are around 40°C or 104°F.
- Trust in your instinct. Whether the breast milk’s been reheated or not, if it looks, smells, and tastes weird, don’t use it.