• Congenital lactose intolerance – evident from birth¹
  
• Primary lactose intolerance – normally becomes apparent after 5 years of age^2-4
• Secondary lactose intolerance – can occur following damage to the gut²

Sufferers display gastrointestinal symptoms, which can be confused with other conditions such as delayed cows’ milk allergy (CMA)⁴. Treatment depends on the type of lactose intolerance but generally involves reducing or removing lactose from the diet⁵.

Lactose intolerance is a digestive problem where the body is unable to digest lactose, a sugar mainly found in milk and dairy products^2,5 This is usually as the result of an absence or deficiency of lactase, an enzyme that breaks down lactose into glucose and galactose, which are more easily absorbed into the bloodstream^1-3.

This rare condition is caused by the absence of lactase from birth . Babies born with congenital lactose intolerance cannot tolerate any breastmilk or infant formula³.

Associated with a developmental decline of the lactase enzyme which gradually occurs after weaning^4,8. Primary lactose intolerance is uncommon before 2–3 years of age and normally becomes apparent after 5 years of age^2-4. It is also uncommon in white Northern Europeans, who are more used to dairy in their diet, whereas it is very prevalent in some ethnic groups who historically have eaten little dairy^2-4. In the UK, it’s more common in people of Asian or African-Caribbean descent¹.

Occurs after damage to the brush border of the gut where lactase is produced, e.g. during acute gastroenteritis, persistent diarrhoea or coeliac disease. This type of lactose intolerance can occur at any age but is more common in infancy. It is usually temporary and once the underlying problem is resolved, lactose can be reintroduced^1-4.

In addition to these three main types of lactose intolerance, there is also ‘developmental lactose intolerance’. This occurs in premature infants, when lactase is deficient in the gut until 34 weeks’ gestation^2-4.

Lactose intolerance causes gastrointestinal symptoms such as diarrhoea, cramping and bloating. These are the result of any undigested lactose passing into the large gut. The undigested lactose has an osmotic effect, drawing in water, leading to diarrhoea. It is then fermented by the bacteria in the gut, producing gas, which causes bloating and cramping^2,5,7.

Lactose intolerance has some similar symptoms to delayed cows’ milk allergy (CMA), so the two conditions are often mistaken for each other^1,2,8. Take a look at our article ‘The differences between lactose intolerance and CMA’ to find out more.

There are no official UK guidelines on the treatment of lactose intolerance in infants or adults. Depending on the type of lactose intolerance, treatment can either involve the reduction or removal of lactose in the diet, while achieving optimal nutritional intake¹. Even if lactase levels are reduced by 50%, individuals can still digest a significant amount of lactose^3,9.

Lactose must be completely removed from the diet and a lactose-free formula must be used for infants^3,5.

Children may be able to consume small amounts of lactose without experiencing symptoms.
In other cases, where lactose may need to be avoided completely, care should be taken to ensure that their diet is still nutritionally balanced. For formula fed infants under one year, a lactose free formula may be used¹.

Opinion on the treatment of secondary lactose intolerance varies. The American Academy of Pediatrics suggests that it “generally does not require elimination of lactose from the diet but, rather, treatment of the underlying condition”². Other healthcare professionals recommend total lactose avoidance until lactase production resumes after the underlying cause has been resolved⁵.

Here are three lists covering foods and ingredients which contain lactose, foods which may contain lactose and some low-lactose alternatives:

• Milk, milk solids, condensed milk, modified milk, evaporated milk, skimmed milk powder
• Butter, buttermilk, margarine
• Cream, artificial cream, ice cream
• Cheese, quark, curd, dairy yogurt
• Whey powder, lactose, lactoglobulin

• Processed meats and foods, e.g. ham
  
• Bread and bread products
• Breakfast cereals
• Cakes
• Biscuits

Avoiding lactose by restricting dairy foods in the diet can lead to an insufficient intake of calcium and other key nutrients, impacting on healthy bone development.

At birth, the skeleton has only 20–30g of calcium and approximately 150mg of calcium is deposited in the bones each day until the age of about 20. If calcium intake is insufficient when bones are growing and developing, they may never reach full strength or peak bone mass. Other nutrients key to bone health are phosphorus, magnesium, vitamin D, and protein^10,11.

It is therefore important to ensure these nutrients are supplied through other foods or supplements.

Lactose intolerance is a condition that can have a serious effect on an infant’s health and development. However, by understanding its symptoms and the treatment options available, healthcare professionals can help parents manage their children’s condition effectively.