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Whether you're exclusively pumping, building up a freezer stash before returning to work or headed on a romantic getaway, being able to pump and store your breast milk can be hugely helpful for nursing moms. But it's not uncommon to notice changes in the appearance, smell or taste of your breast milk after it has been in the refrigerator or freezer for some time.
If your stored breast milk smells or tastes soapy or metallic, you might wonder what's causing those changes, as well as whether you can still offer it to your baby. One possible culprit is excess lipase activity in your milk, also called high lipase breast milk.
The good news? If you do have excess lipase activity in your breast milk, there are strategies that can help manage changes in its smell or taste, and there's no need to throw out your pumped milk — it's still perfectly safe for your baby to drink.
What is high lipase breast milk?
Lipase is an enzyme that breaks down the lipids — or fats — in breast milk. There are two types of lipases: lipoprotein lipase and bile salt-dependent lipase. Each type has in important role to play in your baby's digestion. Lipase helps support your little one's digestive functioning, assists in breaking down triglycerides to release fat-soluble nutrients and protects against infection.
But when lipase activity is excessively high, it breaks down fat too quickly, which can lead to breast milk that tastes or smells soapy or metallic. These changes can be noticeable after your milk has been pumped and stored.
Only a small number of women have excess lipase activity in their breast milk. If you do have high lipase breast milk, know that there's nothing wrong with you or your milk. Most importantly, it does not have a negative effect on your baby: High lipase breast milk is still safe and nutritious for your little one to drink.
How can you tell if you have high lipase breast milk?
Changes in your milk's smell, taste or appearance don't necessarily mean you have excess lipase activity. First, try making sure your pump parts are thoroughly cleaned after each session. It's also a good idea to check with your pediatrician or a certified lactation consultant to rule out any other possible causes.
If you do have excess lipase activity in your breast milk, you might notice a difference in its smell and taste about 12 to 14 hours after pumping and storing, although others might not notice changes until days later.
Some possible changes include:
- Milk that has a soapy smell or taste
- Milk that has a metallic smell or taste
- Milk that has a fishy or sour smell or taste after it's been thawed, or after about 24 hours of being stored it in the refrigerator
Encouraging your baby to drink high lipase breast milk
If you have excess lipase activity, your breast milk is still safe for your baby, and many little ones will drink it without any issues. However, other babies might refuse high lipase breast milk after it has been pumped and stored, which can be incredibly frustrating to busy parents.
If your baby is not a fan of the taste or smell of your breast milk, try these strategies:
- Try the 50/50 approach. Mixing half stored milk with half freshly pumped or expressed milk might satisfy your baby since the soapy or metallic taste will be less strong.
- Scald your pumped milk. Scalding your breast milk might reduce the flavor and smell changes associated with high lipase breast milk. To do so, heat milk in a clean pan (not the microwave) until it's bubbling but not boiling, then place the pan in a bowl of ice water to help cool it down before serving it to your baby.
- Serve room temperature or chilled instead of warmed. Serving your milk chilled instead of warm might also help mask the taste.
- Mix breast milk with solids. If your baby has started solids, which the American Academy of Pediatrics (AAP) recommends around 6 months if your pediatrician has given you the green light, you can try mixing your breast milk with purées to give them a nutritional boost.
- What to Expect When You’re Expecting, 5th edition, Heidi Murkoff.
- What to Expect the First Year, 3rd edition, Heidi Murkoff.
- WhatToExpect.com, How to Hand Express Breast Milk, July 2020.
- WhatToExpect.com, How to Store Breast Milk: Breast Milk Storage Guidelines, August 2020.
- WhatToExpect.com, Foremilk and Hindmilk Imbalance, August 2020.
- Centers for Disease Control & Prevention, Proper Storage and Preparation of Breast Milk, June 2021.
- Centers for Disease Control & Prevention, When, What, and How to Introduce Solid Foods, December 2020.
- La Leche League International, Milk Issues, 2021.
- Mayo Clinic, Breast Milk Storage, Do’s and Don’ts, February 2021.
- National Institutes of Health, National Library of Medicine, Variations in the Rancid-Flavor Compounds of Human Breastmilk Under General Frozen-Storage Conditions, March 2018.
- National Institutes of Health, National Library of Medicine, Biological Underpinnings of Breastfeeding Challenges: The Role of Genetics, Diet, and Environment on Lactation Physiology, August 2016.
- National Institutes of Health, Eunice Kennedy Shriver Institute of Child Health and Human Development, Other Breastfeeding and Milk FAQs, January 2017.
- Krystal Duhaney, R.N., International Board Certified Lactation Consultant, and Founder/CEO of Milky Mama, Rancho Cucamonga, CA.
- Micah Resnick, M.D., F.A.A.P., a board-certified pediatrician at Mount Sinai Doctors in Queens, NY, and at the Mount Sinai Kravis Children’s Hospital in New York, New York, and a member of the What to Expect Medical Review Board.
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I don't know what's going on with my breastmilk. Freshly expressed milk smells fine but sometimes it smells like rotten eggs after being stored in the fridge after about 24 hours. I thought the fridge might not be cold enough so I turned the temperature down, put the milk way in the back and that didn't work. I thought maybe I wasn't using the right container but it smells like that after being stored in plastic or stainless steel. I thought maybe it's something I ate but my diet hasn't changed one bit. Nothing new or different.
A LLL counselor and a lactation consultant told me to scald my milk, because it seemed I was producing too much lipase, BUT 2 things: 1- too much lipase makes the milk taste soapy or rancid. My milk doesn't smell soapy or rancid, it smells like rotten eggs or sulfur!! 2- I would have had this problem from day one and with every feeding because lipase does not vary during different feedings or stages of breastfeeding. I've been breastfeeding for 7 months and this just started to happen, sometimes.
Last night I went to get my LOs bottles ready for today and found that most of my milk smelled bad!! The bottle from Wednesday and Friday smelled bad but not the one from Thursday! I don't get it! I had to dump over 25 ounces of milk down the drain. I almost burst into tears when I did that. BF working moms know, that milk is priceless!! Not to mention, I ran out of reserves so I freaked out about what to feed my LO. I know it won't kill him to take formula but it's really important to me to keep giving him my breastmilk for as long as humanly possible.
What the heck is going on?!?!?!