Discovering a sour taste in expressed breast milk can be unsettling for mothers. It’s a common concern, raising questions about the milk’s quality and safety for the baby. While surprising, the taste change can stem from various factors, many of which are benign and do not indicate a problem.
Common Causes of Sour-Tasting Breast Milk
One frequent reason for breast milk developing a sour or soapy taste after expression and storage is the activity of an enzyme called lipase. Lipase naturally present in human milk, plays a role in breaking down fats, making them more digestible for the baby. When milk is expressed and stored, lipase continues this process, and in some mothers, higher levels of this enzyme can lead to a more noticeable change in taste or smell, often described as soapy, metallic, or sour. This alteration occurs even when milk is stored correctly and does not mean the milk is spoiled.
The mother’s diet can influence the taste of breast milk. Certain foods or drinks, such as spicy dishes, strong-flavored vegetables like garlic or onions, or some vitamins and supplements, can pass through to the milk. These dietary influences can occasionally contribute to a taste a mother perceives as slightly sour or unusual. Such changes are temporary and depend on recent consumption.
Improper storage practices are another cause for taste alteration, leading to genuine spoilage. Breast milk is a biological fluid and requires specific conditions to prevent bacterial growth. Storing milk at incorrect temperatures, such as leaving it out for too long at room temperature, or using unclean containers, can promote the rapid multiplication of bacteria. This bacterial growth breaks down milk components, producing byproducts that result in a distinctly sour, rancid smell and taste, indicating the milk is no longer safe.
An infection in the mother, such as mastitis, might affect the taste of breast milk. Mastitis involves inflammation of the breast tissue, often due to a bacterial infection. While the primary symptoms are pain, redness, and swelling, the presence of bacteria and inflammatory responses within the breast can alter the milk’s composition. These changes might lead to a different taste or smell in the milk expressed from the affected breast, though this is secondary to the more prominent physical symptoms.
Safety of Sour Breast Milk for Baby
Determining whether sour-tasting breast milk is safe for a baby depends on the underlying cause of the taste change. Milk that tastes sour due to high lipase activity is safe for consumption, even if its taste or smell has changed. The nutritional content of milk with high lipase remains intact, and the enzyme activity is a natural process. However, some babies might refuse to drink this milk due to the altered taste.
Conversely, breast milk that tastes sour due to spoilage from improper handling or storage is not safe for the baby. Spoiled milk has undergone bacterial degradation, which can lead to gastrointestinal upset in infants. A baby might react to spoiled milk with fussiness, refusal to feed, or more severe symptoms like vomiting or diarrhea.
Mothers can use visual and olfactory cues to differentiate between safe, lipase-affected milk and unsafe, spoiled milk. Lipase-affected milk might separate into layers, but it smells soapy or metallic, not rancid or putrid. Spoiled milk, on the other hand, has a foul, rancid, or sour odor, similar to spoiled cow’s milk, and may appear chunky or curdled with separation that does not mix back together easily.
When to Seek Professional Guidance
It is advisable to seek professional guidance if there are clear indications of milk spoilage beyond just a taste alteration. If expressed breast milk exhibits a foul, rancid smell, or has a chunky, curdled appearance that does not resemble milk separation, it should be discarded. Mothers should also consult a healthcare provider if their baby experiences symptoms such as persistent vomiting, severe diarrhea, or signs of illness after consuming breast milk, as these could indicate the ingestion of spoiled milk.
Maternal symptoms should also prompt a consultation with a healthcare professional. If a mother experiences signs of a breast infection, such as a fever, red streaks on the breast, breast pain, or flu-like symptoms, these warrant medical attention. An underlying infection like mastitis requires treatment and can affect milk quality.
Consulting a healthcare provider or a lactation consultant is also recommended if the sour taste in breast milk is persistent, unexplained by common causes, or causes concern. A lactation consultant can provide personalized advice on milk handling, storage techniques, and strategies for managing high lipase activity if it is leading to milk refusal by the baby. They can help ensure proper practices and address feeding challenges.