Symptoms and causes

  1. Lactose intolerance is not a food allergy.
  2. Lactose intolerance can be a trigger of irritable bowel syndrome.
  3. Lactose malabsorption can be a consequence of gluten hypersensitivity.

What is it?

Lactose is a sugar mainly present in milk and dairy products. Lactose consists of two components, namely galactose and glucose.

Under normal circumstances, lactose separates into glucose and galactose at the small intestine through an enzyme (i.e. lactase). Both end up in the blood through the intestine.

Lactose malabsorption occurs when the enzyme activity is insufficient to separate the lactose. Lactose consequently ends up in the colon in an undigested state, where it is broken down by the intestinal bacteria. This degradation process gives rise to the symptoms of lactose intolerance.

What is the difference between lactose malabsorption
and intolerance?

Lactose malabsorption indicates insufficient absorption of lactose at the level of the small intestine, so that it ends up undigested in the large intestine.

Lactose intolerance indicates the inconveniences and symptoms associated with the consumption of milk and dairy products. This is usually due to lactose malabsorption, but not always. Sometimes lactose malabsorption does not cause any symptoms.

Complaints and symptoms

Symptoms of patients who have lactose intolerance often include:

  • stomach cramps
  • diarrhoea
  • flatulence
  • bloated feeling

Diagnosis and treatment

Testing of lactose malabsorption

The Gastrointestinal Diseases Department of Maria Middelares General Hospital uses the 13-breath test. The patient takes labelled lactose (13, non-radioactive isotope) and then blows it into a bag every half hour. If lactose separates normally in the small intestine, the 13 marker enters the bloodstream and into the breathing air through the lungs. In people with lactose malabsorption, insufficient 13 enters the air being breathed in. This procedure takes about three hours.


Avoid foodstuffs containing lactose

  • Read the packaging and pay attention to words like ‘lactose’, ‘dry milk powder’ and ‘whey powder’
  • Some products may be well tolerated if the quantity absorbed at once is not too great.

Lactose is mainly found in:

  • dairy products (milk, cream, soft cheese, etcetera)
  • milk bread, raisin bread, sandwiches, croissants, coffee cakes, rusk, toast...
  • pastries, biscuits, waffles, pancakes...
  • chocolate (white and milk), candy...
  • sauces, soups...
  • all kinds of ready-made dishes
  • medication, vitamin preparations
  • cornstarch, pudding powder...
  • sausage, hamburger, minced meat, pâté, salami, beef tartare...
  • ice cream
  • butter, some types of margerine

Advice from a dietitian is certainly useful. For this, you can contact the dietitians of our hospital:


There are enzyme supplements that can be taken with foods containing lactose. Enzyme supplements aid in the digestion of the food. Sometimes, extra calcium and vitamin D supplements are recommended.

Treatment centres and specialisations

Digestive Centre

Latest publication date: 05/02/2021
Supervising author: Dr Vanderstraeten Erik, Dr Degraeuwe Jelle