Lipase is a naturally occurring enzyme in human breastmilk that plays a fundamental role in the digestion of dietary fats for infants. It begins the process of breaking down milk fat, making the resulting fatty acids and glycerol readily available for the baby’s developing system. When parents pump and store milk, a common concern is “high lipase,” which refers to an elevated concentration or activity of this enzyme. This variation often leads to questions about whether the milk remains safe or if it might cause digestive issues like diarrhea.
Understanding Lipase and Its Function
The primary function of lipase, specifically bile salt-stimulated lipase (BSSL), is to hydrolyze triglycerides, the main form of fat stored in the milk. This process breaks down triglycerides into smaller components: free fatty acids and glycerol. This action is crucial for optimal nutrient absorption, as the infant’s maturing digestive tract relies heavily on the milk’s inherent enzymes to assist with fat breakdown.
The presence of BSSL ensures the baby can efficiently utilize the energy-dense fat content of the milk, supporting rapid growth and neurological development. Lipase activity is highly variable among individuals; “high lipase” milk simply possesses a higher concentration or greater speed of action of this enzyme. This variation is a normal physiological difference and does not indicate an underlying health problem in the parent, nor does it make the milk unsafe.
High Lipase Milk: The Taste, Not the Gut
High lipase breastmilk is not considered a cause of diarrhea or severe gastrointestinal distress in the infant. The enzyme’s digestive action is a natural process intended to happen within the baby’s stomach and small intestine, aiding digestion without causing irritation. Confusion arises because the fat breakdown process continues outside the body when milk is stored, leading to noticeable changes in the milk itself.
When lipase acts on triglycerides in stored milk, the accumulation of free fatty acids dramatically changes the milk’s sensory profile. This chemical change results in the milk acquiring a distinct soapy, metallic, or rancid odor and flavor after refrigeration or thawing. This altered taste and smell, rather than a digestive problem, frequently causes babies to reject previously accepted stored milk. Caregivers often misinterpret the baby’s refusal as the milk causing stomach upset, when the baby is simply reacting to the unappealing flavor profile.
Common Causes of Diarrhea in Breastfed Infants
Since high lipase activity does not lead to true diarrhea, parents should consider other common causes if their infant exhibits excessively loose or frequent stools. One frequent cause is acute gastroenteritis, often triggered by viral infections like rotavirus or norovirus, which disrupt the intestinal lining’s absorptive function. Bacterial infections are also possible, though less common, and typically present with other symptoms such as fever, vomiting, or lethargy.
Another factor is the transfer of food allergens from the parent’s diet into the breastmilk, with cow’s milk protein being the most common culprit. The infant’s immune system may react to these proteins, causing inflammation in the gut lining that results in watery stools, sometimes accompanied by mucus or blood. Eliminating the offending protein from the parent’s diet often resolves the symptoms.
A non-infectious, non-allergic cause often mistaken for true diarrhea is a simple foremilk/hindmilk imbalance. This occurs when an infant consumes a large volume of lower-fat, higher-lactose foremilk without reaching the energy-dense hindmilk. The rapid influx of lactose can overwhelm the baby’s lactase enzyme, leading to a temporary lactose overload in the gut. This results in characteristic frothy, green, and watery stools, which are a functional issue rather than a true pathology.
Practical Management of High Lipase Milk
For parents dealing with the taste alteration caused by high lipase activity, the enzyme can be deactivated before it ruins the milk’s flavor. The most effective method is scalding the milk immediately after pumping, before the lipase has time to break down the fats. This involves gently heating the fresh milk on a stovetop until small bubbles form around the edges, reaching a temperature between 140°F and 150°F (60°C to 65°C).
This controlled heating denatures the lipase enzyme, preventing further fat hydrolysis and preserving the milk’s original taste profile. Following scalding, the milk must be rapidly cooled before it is frozen or refrigerated. This technique ensures that the stored milk remains palatable and acceptable to the infant upon thawing.