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Lactose intolerance in babies and children: when it is not a cow's milk protein allergy

Updated: Jun 6, 2023

Lactose Intolerance, Cow's Milk Allergy, Non-IGE mediated Cow's Milk Allergy (formally CMPI Intolerance); it can be a confusing space especially when it comes to babies and infants, which is why it is so important to use a qualified professional to assist in the assessment and management of any allergy or intolerance. Specifically this post is all about Lactose Intolerance, the types of lactose intolerance and what we commonly see in babies and children (I will discuss Cow's Milk Allergy in a later post).

There are 4 main types of lactose intolerance (lactose intolerance and lactose sensitivity are the same thing):

  1. Congenital lactase deficiency. This is an extremely rare genetic disorder where a baby is born without the lactase enzyme. It can be serious with malabsorption causing failure to thrive and dehyration. Management of this condition will be determined by a paediatrician.

  2. Neonatal lactase deficiency. This can present in pre-terms <34 weeks and it typically resolves; breastfeeding is still recommended

  3. Secondary lactose intolerance. This is usually a short term condition after infections like gastro/infectious diarrhoea or other underlying causes like unmanaged Coeliac disease or underlying allergy, which has caused inflammation of the small intestine which then erodes the lactase enzyme which is used for digestion of lactose. Treatment of the underlying condition is required and symptoms of lactose intolerance typically resolve. The average recovery time for the gut of a baby to heal after gastro is 4 weeks (breastfeeding will promote gut healing). A baby with these symptoms of lactose intolerance should not be taken off the breast, you can and should still breastfeed.

  4. Primary Lactose Intolerance. This usually presents at an average 2-3 years of age if including all population groups, but generally happens around 4-5 years of age, as the lactase enzyme gradually starts to decrease (by this age a child is usually fully weaned). About 70% of people have this type of lactose intolerance and will usually tolerate varying amounts of lactose.

Lactose intolerance in babies:

Firstly it is not common for a baby under 12 months to have a lactose intolerance (sensitivity), unless as mentioned above they have a rare genetic disorder or neonatal lactase deficiency, or potentially a secondary lactose intolerance (which is temporary) due to other underlying conditions. This is because lactose is the main carbohydrate in breast milk and there is more of it in g/ml than compared to cow's milk; breast milk contains 7.4g of lactose per 100ml and cow's milk contains 5g of lactose per 100ml. Due to this babies are primed to digest lactose, and their small intestines are lined with the enzyme lactase (thank goodness otherwise they would not be able to digest breast milk). When lactose (C₁₂H₂₂O₁₁) is consumed it is broken down in the small intestine by the enzyme lactase, almost all infants have the enzyme lactase and can digest lactose from birth.

Lactose overload (not an intolerance, remember true lactose intolerance is very rare) can sometimes be seen in infants < 3 months of age, usually a baby is unsettled and consuming large amounts of breastmilk, and their mothers have an oversupply. This can usually be easily fixed in a few days with an adjusted breastfeeding regime (see a lactation consultant) and while continuing to breastfeed, breastmilk is still recommended as the best choice for your baby.

Lactose overload symptoms can sometimes be confused with symptoms of Cow's Milk Allergy, it is important to get a correct diagnosis.

Lactose Intolerance in Children:

In older children typically we see Primary Lactose Intolerance present around 2-5 years of age, although again this can be confused with cow's milk protein allergies, and the symptoms may overlap. Common symptoms of lactose intolerance include bloating, diarrhea, wind, and pain after eating foods high in lactose. Lactose intolerance can be diagnosed with a breath test or a clinician-led elimination protocol by a Paediatric Dietitian. It is treated by lowering the amount of lactose in the diet, however, every child is different and children will tolerate different amounts of lactose; some children can tolerate a small amount, while others are very sensitive. Your child’s symptoms will help you decide how strict you need to be. To get a correct diagnosis use a trained paediatric Dietitian or Doctor/Paediatrician. Education on how to avoid lactose, food substitutes, and any re-introduction of lactose should be completed by a Paediatric Dietitian.

Secondary Lactose Intolerance

Secondary lactose intolerance can occur in babies and children usually after a severe bout of gastro or infectious diarrhea, it can also occur if there are undiagnosed conditions such as allergies or coeliac disease which cause inflammation in the intestine. This is because the enzyme lactase is produced on the tips of the brush border of the intestine (villi) so any damage or inflammation of the gut lining may cause secondary lactose intolerance.

Secondary lactose intolerance is temporary, as long as the intestine can heal. Continuing to breastfeed in this situation is always recommended, and will not harm your baby as long as she is otherwise well and growing normally. Breastfeeding will aid in gut healing.

If a baby or toddler has had a severe bout of gastro or infectious diarrhea and there is secondary lactose intolerance (discuss this with your health professional), it can be helpful to reduce high lactose foods and using lactose-free milk (this should not replace breastmilk or infant formula in children <12 months of age), whilst the gut heals for a short term eg 1-3 weeks. If they have prolonged symptoms of diarrhea, this should be discussed with your healthcare provider.

A few very important points to remember:

  1. A mother cannot reduce the amount of lactose in her breastmilk by eliminating cow's milk from her diet (nor does she need to, remember babies are primed to digest lactose)

  2. Delaying the introduction of dairy foods in an infant's diet when starting solids will not improve their tolerance to lactose or dairy. Dairy is an allergen and is recommended to be introduced before 12 months of age.

  3. Lactose intolerance is very different from Cows Milk Allergy (IGE and Non- IGE mediated) however the symptoms may overlap, it is important to see a qualified professional to get a correct diagnosis, either Paediatric Dietitian or Paediatrician.

  4. In almost all cases* of lactose intolerance, breast milk remains the best choice for your baby.

x Anna

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