L’intolérance au lactose


Lactose intolerance is a malabsorption of lactose caused by a deficiency in lactase, the enzyme responsible for its digestion. Lactose is a disaccharide made up of two monosaccharides, glucose and galactose. During digestion, lactose is divided into its two components under the action of the enzyme lactase. With lactase deficiency, lactose cannot be digested or absorbed and remains whole in the intestine. This causes a lot of water to enter the intestine, followed by bacterial fermentation of lactose and the production of gases (hydrogen, carbon dioxide and methane) leading to gas and abdominal pain.


There are three types of lactase deficiency:

  • Congenital lactase deficiency (e.g. rare lactase deficiencies).
  • Primary or acquired lactase deficiency. It is the most common form of lactase deficiency. It is caused by the decrease in lactase levels with age.
  • Secondary lactase deficiency. This is a lactase deficiency that can be caused by a disease that affects the intestinal mucosa (eg celiac disease), an intestinal infection (eg gastroenteritis) or by surgery on the stomachs. intestines.


Symptoms of lactose intolerance may include abdominal pain and cramping, abdominal bloating or distension, gas or gas, diarrhea, nausea, and rumbling (gurgling sounds due to the movement of gas in the intestine ).

Intolerance versus allergy

It is important to differentiate lactose intolerance from milk allergy. Lactose intolerance is a poor digestion of lactose due to lactase deficiency and accompanied by symptoms (eg, diarrhea, gas, abdominal pain). A milk allergy is a reaction of the immune system to proteins in milk. People who are allergic to milk can digest lactose normally, it is the proteins in the milk that trigger the allergic reaction.

Individual tolerance

The degree of lactose intolerance can vary between individuals. Indeed, depending on individual tolerance, the speed of gastric emptying, the time of intestinal transit and the absorption capacity of the colon may be different from one person to another. Finally, factors such as age (decrease in the enzyme lactase with age), ethnicity (e.g. more than 90% of Asians are lactose intolerant) and the form of the food (e.g.: milk versus yogurt, naturally less rich in lactose) can also have an influence on the degree of lactose intolerance.

Nutritional treatment

Lactose intolerance can be controlled with alactose free diet. However, as mentioned above, the degree of lactose malabsorption can vary from person to person. Additionally, many people with lactase deficiency can tolerate up to 250-375 mL of milk before experiencing symptoms. As a result, nutritional recommendations should be personalized according to the needs and tolerance of each individual. In general, strategies that can be used to prevent the symptoms of lactose intolerance include:

  • Ingest small amounts of lactose at a time.
  • Consume milk or dairy products with other foods during meals and / or snacks.
  • Choose dairy products containing less lactose, such as yogurts and hard or aged cheeses.
  • Opt for milk and dairy products without lactose or with a reduced lactose content.
  • Take lactase enzyme tablets as needed.

It is also important to ensure that lactose intolerant individuals meet their calcium and vitamin D needs. This can be done through diet and / or supplementation. Finally, the strategies listed above are general recommendations, it is always best to consult a dietitian for personalized nutritional recommendations based on your specific needs.



Bouthillier, Lise. January 2019. Diseases of the digestive tract. NUT 2047 Clinical nutrition 2. Montreal: University of Montreal.al.





Article written by:

Marie-Noël Marsan, Nutritionist


AlimentationMaladies digestives

Leave a comment

All comments are moderated before posting