Secondary Lactose Intolerance in the Breastfed Baby

Published on: July 14, 2017

How to recognize it and what to do if your baby has secondary lactose intolerance. By Fran Safaie   You’ve probably heard of lactose intolerance before, since, in adults, it’s a reasonably common digestive problem. Known as late-onset lactose intolerance, it occurs when, over a number of years, a person’s body begins to slowly decrease in their production of lactase, the enzyme that breaks down lactose. The body then becomes unable to digest lactose, a type of sugar mainly found in milk and dairy products. But how might lactose intolerance affect infants, who for the first six months of life rely exclusively on milk for their nutrition and as their main source of nutrition even after solids have been introduced? And what might cause them to be unable to tolerate the most abundant component found in human milk?

Rare primary lactose intolerance

On very rare occasions, babies can be born with primary lactose intolerance. Because milk is the natural first food of all humans, babies are typically born ready, willing and able to drink and digest milk. Primary lactose intolerance is an incredibly rare, inherited metabolic disorder. In Finland, where this autosomal recessive disorder is said to be excessively common, only 16 reported cases were recorded over a period of 17 years (Savilahti et al, 1983). With this type of lactose intolerance, babies are born with a lack of the enzyme, lactase. It’s a serious condition that becomes apparent soon after birth. A baby with primary lactose intolerance would not thrive and would show obvious symptoms of malabsorption and dehydration and would require a special lactose-free formula to survive.

Developmental lactose deficiency

Babies who are born prematurely can also suffer from a form of lactose intolerance called developmental lactose deficiency because their bodies have not started producing their own lactase, which typically increases during the third trimester. However, this resolves with time as the infant’s system matures and ingesting lactose can help to accelerate this maturation process.

Most common: Secondary lactose intolerance

Far more commonly, infants can experience periods of secondary lactose intolerance. This type of lactose intolerance occurs when irritation to the gut lining occurs. Since lactase is produced in the villi, which are the very tips of the microscopic folds in the gut, even very subtle damage to the gut can affect the delicate villi and thus go on to reduce the amount of lactase produced, resulting in secondary lactose intolerance.
The solution is to find out what caused the secondary lactose intolerance and tackle that, rather than to attempt to eliminate lactose.
Damage to the villi commonly occurs through an infectious, allergic or inflammatory process, for example, as a result of:
  • A food sensitivity: In breastfed babies, this can come from food proteins, such as in cow’s’ milk, wheat, soy or egg, or possibly other food chemicals that enter breastmilk from the mother’s diet, as well as from food the baby has eaten.
  • Gastroenteritis
  • Antibiotic use
  • The oral rotavirus vaccine
  • A parasitic infection
  • Coeliac disease
  • Crohn’s disease
  • Bowel surgery

So, what does secondary lactose intolerance look like?

Well, it can vary, but typically you might expect liquid, frothy stools which are sometimes green, due to the rapid transit through the digestive system with stringy mucus. Your baby may also be more irritable and gassy than usual.

What can we do about secondary lactose intolerance in the breastfed infant?

The solution is to find out what caused the secondary lactose intolerance and tackle that, rather than to attempt to eliminate lactose. Bear in mind that lactose is present in ALL breastmilk, no matter what diet the mother consumes. It is also present in much the same quantities in both foremilk, the watery milk present at the beginning of the feed, and in the hindmilk, the richer milk with a higher fat content that is present at the end of the feed.

For formula-fed infants

In a formula-fed infant, a quick switch to lactose-free formula will cause a reduction in symptoms as the gut heals.

For breastfed infants

However, human milk remains the best food for babies and will assist with gut healing, so, for a breastfed infant, replacing breastmilk with a lactose-free formula is NOT the solution unless there are serious concerns about the infant’s growth. As breastmilk can help to heal the gut, in the vast majority of cases, it is important for breastfeeding to continue.

Gut healing times

Gut healing times can vary, depending on cause and age of the infant. For example, the gut of a baby with severe gastroenteritis will take four weeks on average to heal, but that could double for a baby under 3 months. For babies over 18 months, recovery may be as rapid as one week.

Seek professional advice

Whatever your baby’s age, you should always seek professional advice from a pediatrician and/or lactation specialist before introducing lactose-free formula. Except for the very rare primary type, lactose intolerance in babies always has a cause. Establishing the cause and fixing that is the key to resolving the baby’s symptoms.  


About the Author

Fran is a doula trainer for Childbirth International and Mongan Method HypnoBirthing Practitioner from the UK. Fran been drawn by the siren call of Southeast Asia many times, traveling extensively. She has lived in Bangkok with her husband since 2013 and birthed their son here in 2016. Likes: Sauvignon Blanc. Dislikes: The Patriarchy.
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