Is my baby lactose intolerant?

By Kelly Bonyata, BS, IBCLC

If your baby is sensitive to dairy products it is highly unlikely that the problem is lactose intolerance, although many people may tell you so.

There are three types of lactose intolerance:

  1. Primary lactose intolerance
  2. Congenital lactose intolerance
  3. Secondary lactose intolerance

Primary lactose intolerance (also called developmental, late-onset or adult lactose intolerance) is relatively common in adults (and more common in some nationalities than others), and is caused by a slow decrease in the body’s production of lactase, the enzyme that breaks down lactose (milk sugar). This occurs gradually, over a period of years, and never appears before 2-5 years old and often not until young adulthood. Almost all adults who are lactose intolerant have this type of lactose intolerance, which is not related to lactose intolerance in babies.

Congenital lactose intolerance and similar congenital disorders

  • Congenital lactose intolerance is very rare and is an inherited metabolic disorder rather than an allergy. This disorder is generally apparent within a few days after birth and is characterized by severe diarrhea, vomiting, dehydration and failure to thrive. It resolves after the age of six months.
  • A similar, less severe, metabolic disorder is congenital lactase deficiency. This disorder, apparent within 10 days of birth, occurs when brush-border lactase activity (required for the digestion of lactose) in the small intestine is low or absent at birth and is characterized by diarrhea and malabsorption. It is also very rare.
  • Galactosemia is another rare metabolic disorder that occurs when the liver enzyme GALT, needed to break down galactose, is partially or completely absent. Although this disorder does not directly concern lactose, babies with the more severe forms of galactosemia will not be able to tolerate any lactose since lactose is formed from the two sugars galactose and glucose. The classical form of galactosemia (where GALT is completely absent) is characterized by vomiting, diarrhea, jaundice and failure to thrive within a few days after birth. Duarte Galactosemia, a variant of classic galactosemia, is not as severe and baby may be able to be partially or fully breastfed.
  • Some premature babies have a temporary form of lactose intolerance (developmental lactose deficiency) because their bodies are not yet producing lactase. This will go away as baby matures, and in fact the maturation process can be accelerated by baby’s ingestion of lactose. One option is to add lactase to baby’s feedings (instead of switching to lactose-free formula, which is nutritionally inadequate).

Secondary lactose intolerance (also called acquired lactose intolerance) can appear at any age and occurs when the intestinal brush border is damaged by an infectious, allergic or inflammatory process, thus reducing lactase activity. Causes of secondary lactose intolerance include gastroenteritis, food intolerance or allergy, celiac disease (gluten intolerance), and bowel surgery. Per Joy Anderson, IBCLC (in Lactose intolerance and the breastfed baby):

“Anything that damages the gut lining, even subtly, can cause secondary lactose intolerance. The enzyme lactase is produced in the very tips of folds of the intestine, and anything that causes damage to the gut may wipe off these tips and reduce the enzyme production.

“…Secondary lactose intolerance is a temporary state as long as the gut damage can heal. When the cause of the damage to the gut is removed, for example the food to which a baby is allergic is taken out of the diet, the gut will heal even if the baby is still fed breastmilk.”

Although cow’s milk protein sensitivity and lactose intolerance are not the same thing, they can sometimes occur at the same time, since food allergy can cause secondary lactose intolerance.

In addition to the different types of lactose intolerance, baby might also experience a lactose overload, caused by breastmilk oversupply (also called foremilk-hindmilk imbalance).

Lactose Overload can occur in baby when mom has an oversupply of milk. The milk that baby gets earlier in a feeding (foremilk) is higher in lactose and lower in fat than the milk later in the feeding (hindmilk). Per Diana West, IBCLC (in Is my baby’s fussiness caused by the lactose in my milk?):

As baby begins nursing, the first thing he receives is this lower-fat foremilk, which quenches his thirst. Baby’s nursing triggers the mother’s milk ejection reflex, which squeezes milk and the sticking fat cells from the milk-making cells into the ducts. This higher-fat hindmilk mixes with the high-lactose foremilk and baby receives the perfect food, with fat calories for growth and lactose for energy and brain development. However, when milk production is too high, baby may fill up on the foremilk and then have difficulty digesting all the lactose that is not balanced by fat. This is known as foremilk/hindmilk imbalance or oversupply...

Although infants are not lactose intolerant by nature, a high volume of lactose can overwhelm a baby’s digestive system. When there is not enough lactase to break down all the lactose, the excess lactose causes gassiness and discomfort, and frequently green, watery or foamy stools. Over time, large amounts of undigested lactose can irritate the lining of the intestines so that even a little bit passing through can cause irritation. Occasionally, this can result in small amounts of bleeding into stools that can be misdiagnosed as a food allergy. Some pediatricians will mistakenly diagnose lactose intolerance if there is undigested sugar in the baby’s stool.


See also @ :

Dairy and other Food Sensitivities in Breastfed Babies

Additional information

General information

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