Why Does My Breast Milk Taste Sour?

Why Does My Breast Milk Taste Sour?
Why Does My Breast Milk Taste Sour?

Starting a nursing journey is a great experience, but it is not without some surprises. The unexpected sour taste of breast milk is one such surprise that some nursing moms experience. This may cause anxiety. In this blog, we will look at why does my breast milk taste sour? and its effects on both moms and newborns, and a variety of solutions to manage this issue and guarantee a smooth nursing experience.

Breast Milk Flavor

Breast milk is an evolving fluid that adapts to your baby’s changing demands. Breast milk flavor can range from sweet to salty and even a bit harsh. Factors such as the mother’s nutrition, hormone levels, and the infant’s developmental stage determine this difference. The earliest milk produced, colostrum, is noted for its intense sweetness, but mature milk may have traces of flavors from the things you consume.

Why Does My Breast Milk Taste Sour?

The Most Common Causes of Sour Breast Milk
The Most Common Causes of Sour Breast Milk

Sour breast milk can be a cause of concern for breastfeeding mothers. While breast milk is typically fresh and sweet, there are several reasons why it might take on a sour taste. Here are some common causes:

  1. High Lipase Levels:
    Lipase levels in breast milk are higher in some women. Lipase is an enzyme that helps in the breakdown of fats. Even if the milk is properly preserved, high lipase levels might cause it to develop a sour taste over time. This has no effect on the milk’s safety or nutritional value, but some babies may dislike the taste.
  2. Improper Storage:
    If breast milk is not properly preserved, it might get sour. It is critical to keep breast milk in clean containers and to refrigerate or freeze it as soon as possible. If milk is left out at room temperature for a lengthy amount of time or is stored in an unclean container, it may develop a sour flavor.
  3. Bacterial Contamination:
    Breast milk can get contaminated with bacteria if it is not handled or kept properly. To reduce the danger of bacterial contamination, wash your hands well before expressing milk, use clean containers, and adhere to good hygiene standards.
  4. High Levels of Peroxidase:
    Peroxidase levels in breast milk are greater in some women. Peroxidase is an enzyme that plays a role in milk’s immune system properties. Elevated peroxidase levels may lead to a somewhat sour taste, although this does not render the milk dangerous for the infant.
  5. Mom’s Diet:
    Some mothers find that certain foods in their diet can impact the taste of their breast milk. Strongly flavored or spicy foods may cause the milk to take on a different taste.
  6. Thawed or Refrigerated Milk:
    Frozen breast milk may have a different taste after thawing, which some babies may not like. It is recommended to use thawed milk within 24 hours and avoid refreezing it.

If you suspect that your breast milk has turned sour, it’s essential to check for signs of spoilage, such as a rancid or off smell. If the milk smells bad, it’s best to discard it. If you consistently notice a sour taste and it’s affecting your baby’s acceptance of the milk, you may want to consult with a lactation consultant or healthcare provider for guidance.

Effects on Babies

The effects of babies consuming sour breast milk can vary depending on the underlying cause and the baby’s individual tolerance. In general, sour breast milk is not harmful to infants, and many babies will still consume it without any issues. However, there are a few considerations:

  1. Taste Preference: Some babies may not like the taste of sour breast milk, especially if it is caused due to high lipase levels or changes in the mother’s diet. Babies are sensitive to changes in the flavor of breast milk, and they may show reluctance to feed or express dissatisfaction during feeding.
  2. Lipase Issues: If the sour taste is due to elevated lipase levels in the breast milk, it doesn’t pose a health risk to the baby. However, some infants may refuse the milk because of the altered taste. In such cases, mothers can try scalding the milk before storing it to deactivate the lipase, although this may not work for everyone.
  3. Digestive Sensitivity: Some babies may have sensitive digestive systems and could be more affected by changes in the composition or taste of breast milk. If a baby shows signs of discomfort, excessive gas, or fussiness after consuming sour breast milk, it may be worth considering the possibility of digestive sensitivity.
  4. Hygiene and Bacterial Contamination: If the sourness is due to bacterial contamination from improper storage or handling, there could be a risk of the baby ingesting harmful bacteria. In such cases, it’s crucial to ensure proper hygiene practices, including washing hands before expressing milk, using clean containers, and refrigerating or freezing milk promptly.
  5. Mom’s Diet: If the sour taste is related to changes in the mother’s diet, it might be a matter of the baby adjusting to the new flavors. Some infants are more sensitive to changes in the maternal diet, and it may take time for them to get used to the variations in breast milk taste.

If you notice that your baby is consistently refusing or reacting negatively to breast milk with a sour taste, it’s a good idea to consult with a healthcare provider or a lactation consultant.

Strategies and Solutions

Strategies and Solutions
Strategies and Solutions

Sour breast milk can be concerning for breastfeeding mothers, but there are several strategies and solutions to address this issue. Here are some steps you can take:

Check Storage Guidelines

Ensure that you are following proper storage guidelines for breast milk. Freshly expressed breast milk is usually good for up to 4-6 hours at room temperature, up to 4 days in the refrigerator, and up to 6–12 months in the freezer. If breast milk has been stored for too long or not at the right temperature, it may sour.

Proper Cleaning and Sterilization

Ensure that the containers and breast pump equipment you use are thoroughly cleaned and sterilized. Bacteria from improper cleaning can lead to the souring of breast milk.

Use Clean Hands

Wash your hands thoroughly before expressing breast milk or handling storage containers. This helps prevent the introduction of bacteria into the milk.

Avoid Mixing Different Temperatures

Do not mix freshly expressed milk with milk that has been refrigerated or frozen. Mixing at different temperatures can cause the milk to sour more quickly.

Rotate-stored milk

When using stored breast milk, rotate the older batches to the front so that you use them first. This helps prevent the milk from sitting too long and potentially souring.

Check for Lipase Activity

Some women have high lipase levels in their milk, which can cause it to develop a soapy or sour odor over time. If you suspect lipase is the issue, scald the milk before storing it to deactivate the enzyme. To scald, heat the milk until small bubbles form around the edge, then quickly cool and store it.

Thoroughly Clean Pump and Bottles

Ensure that your breast pump and bottles are cleaned thoroughly after each use. Residual milk left in the equipment can lead to contamination and souring.

Monitor Diet

Sometimes, certain foods in a mother’s diet can affect the taste and smell of breast milk. Pay attention to your diet, and if you notice a correlation between certain foods and sour milk, consider making dietary adjustments.

Remember, it’s always a good idea to seek guidance from a healthcare professional for personalized advice based on your specific situation.


While it might seem strange, sometimes breast milk can taste sour. But don’t worry, there are ways to overcome this and make breastfeeding a positive experience for both you and your baby. Every mom and baby have their own journey, and dealing with challenges like sour milk can make the breastfeeding experience even more special.

To make things better, it’s important to understand why breast milk might taste sour and what you can do about it. By learning about the causes and trying the solutions mentioned in this article, you can keep providing your baby with the nourishment they need while enjoying the wonders of breastfeeding.

Remember, each breastfeeding journey is unique, and facing and solving problems can make it more fulfilling. So, embrace the adventure, learn from the challenges, and cherish every moment with your precious little one.