I Had High Lipase Milk—Here’s What That Means

When my daughter was a few months old, my maternity leave ended and I had to return to weekend battle assemblies with my Army Reserve unit. Since I was still breastfeeding, I dutifully pumped for weeks prior to my return date and froze dozens of ounces of milk for my husband to give her while I was gone.

My first morning back at drill, I got a text about two hours in: “She won't take the bottle.”

My heart dropped and I immediately began to panic—What if she won't eat while I'm gone?

Bottle rejection can be an incredibly frustrating and defeating experience for parents who need to be apart from their babies for any reason or length of time. We all want the reassurance of knowing our children will be taken care of in our absence, and when a nursing baby won't take a bottle, it can lead to intense worry. This quickly turned to exasperation when no matter what we tried, my daughter refused to drink the warmed-up milk. She would take a sip, recoil in disgust, and then turn her head away.

After trying half a dozen different nipples and bottles, I was at a loss. In a last-ditch effort to figure out the problem, I took a sip of the milk myself and immediately spat it out—it tasted like soap! Confused and, frankly, grossed out, I scoured the internet and discovered the culprit: high lipase.

My first thought was, What in the world is high lipase? And why do I have it?

What Is High Lipase Milk?

"Lipase is an enzyme that is normally present in human milk. It helps to keep the fat mixed with the whey portion of the milk and keeps fat globules small and more digestible," says Lilly Lan Chang, M.D., MS, FAAP, a neonatologist at the Johns Hopkins All Children's Maternal, Fetal & Neonatal Institute. "By breaking down the milk fat, the fat-soluble vitamins are more available to the infant."

When someone has excess lipase, Dr. Chang explains, “the milk fat begins to break down sooner/faster after expression."

Although the lipase process is normal, at high levels it can cause a metallic or soapy aftertaste, exactly like what I had detected, and make the milk unappealing. The change of taste can happen within a few hours to days. 

Is High Lipase Milk Dangerous to Your Baby?

Dr. Chang points out that while excess lipase can change the taste of the milk, it does not make it harmful to the baby.

In fact, it may even have benefits for your milk. "It actually is protective from microorganisms and keeps the milk from spoiling," says Stephanie Nelson, BSN, RN, IBCLC, CCRN-NICU, and co-owner of Wisconsin-based lactation consultant business Success Lactation Specialists, LLC.

What Causes High Lipase?

While some medical professionals agree high lipase isn't talked about enough, it's hard to say how many people experience it, and it's unclear why some do and others don't. But “once the milk becomes affected by the lipase, there is no way to treat it,” explains Dr. Chang.

Nelson says she sees high lipase clients frequently, and levels can vary widely between people and even from pregnancy to pregnancy, which was also my case.

As far as I know, I didn't have excess lipase with my first baby (or he was just never bothered by it), but did with my second. I also discovered after experimenting a bit that my milk would start to taste soapy after refrigeration alone. As Nelson suggests, some people only have this issue when they freeze their milk. “We do get client calls about refusing previously frozen milk only, and this is often the reason,” she says. But others, like me, can't even store it in the fridge.

What to Do if You Have High Lipase Milk

"If the baby doesn't mind the milk, there's nothing for a family to do about it,” says Nelson. In other words, your baby can safely drink it, regardless of that soapy taste or smell.

But if your baby happens to be one of the picky ones who rejects the milk outright? You can start by masking the taste by adding a few drops of alcohol-free vanilla extract to the milk, or mixing the thawed milk with freshly pumped milk. Keep in mind, the Centers for Disease Control and Prevention advises you cool freshly expressed milk before combining it.

If that doesn't work, Nelson says there are other ways to help. "First, you can deep freeze your milk immediately after it is expressed/pumped, which helps decrease the lipase activity," she says. "The downside is you'd need to freeze it right away as cold as your deep freezer can go, and not all home deep freezing has this capability.” 

Another option is heating the milk, since lipase is inactivated at high temperatures. “You can scald your milk on the stove in a pan prior to freezing to stop the lipase activity,” explains Nelson. You can do this by heating the milk to around 144.5 degrees Fahrenheit for about one minute, or to 163 degrees Fahrenheit for about 15 seconds (a thermostat is recommended), then immediately cooling and storing in the freezer.

Dr. Chang agrees that scalding is a good solution, although it may lower some nutrient levels and decrease the milk's anti-infection properties. However, she adds, this shouldn't be an issue unless all the milk the baby is receiving has been heat-treated.

Scalding my milk (despite being time-consuming and inconvenient) ended up being a lifesaver for me, and the only way my daughter would take a bottle. 

Ultimately, I was relieved to have an explanation and learn there wasn't anything wrong with me or my milk. And once I started talking to other mom friends about it, I was surprised by how many of them had experienced the same issue.

The Bottom Line

If you're a nursing parent who is struggling to get your baby to take a bottle, excess lipase isn't guaranteed to be the cause, but it's definitely worth looking into or discussing with a certified lactation consultant. And even if it turns out to be the cause, there are solutions that can work for your family.