4 symptoms and 5 tests for lactose intolerance: understanding, identifying and managing



Lactose intolerance is a common digestive disorder which affects 75% of the world's population. The symptoms of this condition, which results from a deficiency in lactaselactose, the enzyme needed to digest lactose, include bloating, diarrhoea, flatulence and other digestive discomforts. In this in-depth article, we will explore this disorder in detail, explain how to differentiate it from other digestive problems, discuss methods of diagnosis and explain how to treat it. present solutions such as taking food supplements.

I. Understanding lactose intolerance

1. Definition

Lactose intolerance is a digestive condition in which the body does not produce enough food. d'lactase enzyme to correctly break down lactosemilk sugar. Lactase is produced naturally in the small intestine and is essential for digesting lactose. Babies produce an abundance of lactase to digest their mother's milk, but production gradually declines with age in many people. Lactose intolerance is therefore a natural phenomenon.

2. Lactose and lactase

Lactose is a complex carbohydrate found in milk, made up of glucose and galactose. To be properly digested, lactose must be broken down into these two simple sugars in the digestive tract. This is the role of the enzyme lactase

3. History and development

Lactose intolerance was common among our prehistoric ancestors. After weaning, adults no longer consumed milk, which naturally led to lactose intolerance. However, this was not the case, around 10,000 years agoThe domestication of cattle in the Caucasus led to an increase in milk consumption among adults, which in turn encouraged a genetic mutation that enabled part of the population to continue producing lactase. Today, it is estimated that  40% the number of lactose intolerant people in Europein France, nearly 5 million people are affected by this disorder.


Young lactose-intolerant prehistoric man in front of his cave

And yes, this handsome, dark-haired fellow digested mammoths better than milk 😅

II. Symptoms of lactose intolerance

1. Common symptoms

The symptoms of lactose intolerance result from the fermentation of undigested lactose by intestinal bacteria. The main symptoms include :

a. Bloating

Bloating is caused by the accumulation of gas in the intestine, resulting from the fermentation of undigested lactose. This can manifest itself as abdominal bloating, gurgling, cramping and flatulence. 

b. Heartburn🔥

Heartburn can occur due to the build-up of gastric acid resulting from the fermentation of lactose.

c. Diarrhoea 🚽

Acid diarrhoea is a common and often pressing symptom of lactose intolerance. Lactose fermentation disrupts digestion, which can lead to a precipitous evacuation of the alimentary bolus, with undigested stools, in the 15 minutes to 4 hours following consumption of a milk-based food.

d. Chronic fatigue💤

The symptoms of lactose intolerance, particularly when they are frequent, can lead to chronic fatigue. The body is overworked by the stress associated with the symptoms and the incomplete assimilation of food.

e. More rarely

Nausea, vomiting, constipation and migraines.


Faced with such symptoms, lactose intolerance can represent a real handicap in everyday life. Severe intolerance can lead sufferers to cut themselves off from social life in order to better control their diet. In restaurants or among friends, patience and education are needed, because lactose intolerance is still little known in France.

2. Long-term consequences

The symptoms of lactose intolerance should not be taken lightly. Their recurrence can lead to irritation of the intestinal mucosa, depression and other health problems. Severe intolerance can greatly affect quality of life.


III. Distinguishing lactose intolerance from other digestive problems

It is essential to distinguish lactose intolerance from other digestive problems, as this can have an impact on diagnosis and treatment.

1. Allergy to milk protein 🥛

Lactose intolerance and milk allergy are often confused, even though they are very different. Lactose intolerance is due to a lactase deficiency and does not involve the immune system. Lactose intolerance milk allergy is an immune reaction to certain proteins present in milk, such as casein. Milk protein allergy generally affects infants and disappears naturally around the age of 3.

Immunological reactions to milk allergy are generally more violent than those of lactose intolerance:

  • they may be respiratory (difficulty in breathing due to swelling of the mucous membranes of the respiratory tract: nose, throat), asthma
  • skin (hives, eczema)
  • they can cause bloody diarrhoea in the faeces
  • and, more rarely, anaphylactic shock (extreme allergic reaction in people who are hypersensitive to certain allergens)

Unfortunately, there is no solution to an allergy other than total avoidance of milk protein in any form whatsoever. As for lactose intolerance, there are alternatives such as low-fat or lactose-free diets, or even better : lactase supplementation (more on this later 😉 ).


2. Crohn's disease

Crohn's disease is an inflammatory bowel disease. which can cause a variety of symptoms, including digestive problems. However, the symptoms of Crohn's disease, such as bloody diarrhoea, abdominal pain and intestinal ulcerations, are distinct from those of lactose intolerance.

3. Celiac disease

Celiac disease is an autoimmune reaction to glutena protein found in wheat, barley and rye. Symptoms include digestive problems, but coeliac disease is also different from lactose intolerance. An eviction test will reveal the type of intolerance.

4. Other food intolerances

There are many other food intolerances, including fructose, histamine, FODMAP and sorbitol intolerance. These conditions have specific symptoms and require separate diagnoses.


Young woman on the toilet suffering from acid diarrhoea

Lactose intolerance is not inevitable, and there are solutions available if your intolerance is correctly diagnosed.


IV. 5 diagnostic tests for lactose intolerance

If you suspect lactose intolerance, several diagnostic tests are available. However, it is important to consult a healthcare professional for a precise diagnosis.

1. Eviction test ❌

The eviction test consists of completely eliminating lactose from the diet for a short period of time.usually 4 days. If the symptoms disappear, you are probably suffering from lactose intolerance. Reintroducing lactose will cause symptoms to reappear. It is very important to read the labels and composition of everything you take. Beware of hidden lactose, in charcuterieand in processed foods in general (crisps, ready meals, surimi, etc.).

2. Lactase enzyme supplementation test ⭐

This test involves taking lactase capsules. (Lactolérance 9000) before consuming a dairy product (for example, 1 x 10cl glass of milk or 30g of fromage frais). 

If there are no digestive discomforts in the hours that follow, unlike usual, it's because the lactase has done its job, it is therefore likely that you are lactose intolerant.

If, on the other hand, lactase capsules have not prevented the appearance of the usual intestinal symptoms, then other possibilities than lactose intolerance should be explored.

3. Hydrogen breath test (BHT) 🫁

The hydrogen breath test (Breath Hydrogen Test) is a medical test carried out in hospital or at a medical analysis centre. It is performed on an empty stomach and involves measuring the amount of hydrogen in the air exhaled after drinking a lactose solution. An increase in the concentration of exhaled hydrogen indicates lactose intolerance.

The test takes around 2 hours to complete. and the experience can be unpleasant, depending on how your body reacts after ingesting lactose. However, lactoser offers highly reliable results.

4. Genetic test 🧬

A genetic test can reveal whether you have a hereditary predisposition to lactose intolerance. A blood test or a sample of cells from inside the cheek will tell you whether you have a genetic predisposition to this intolerance. 

However, there are a number of reasons for this, this test is not always conclusiveThis is because it does not reveal acquired lactose intolerance, after heavy medical treatment for example.. The relatively high cost (around €140) is not covered by Social Security.

5. Blood glucose test 🩸

The blood sugar test involves measuring blood glucose levels before and after ingesting a certain amount of lactose. A significant increase in glucose levels after ingesting lactose may indicate intolerance. This test is not widely used.


Young woman and a little girl performing a breath test to diagnose lactose intolerance

The breath test (BHT) is currently the most reliable test for diagnosing lactose intolerance.

V. Managing lactose intolerance on a daily basis

Fortunately, lactose intolerance is manageable. Here are a few strategies:

1. Lactose-free diet

Lactose-free eating at home is pretty easyLactose-free food is a good idea, as long as you read the labels and are wary of processed foods (where lactose is hidden). What's more, there are many lactose-free products on the market: milk, cream, cheese, etc. These products contain added lactase, which makes them easier to digest for people with lactose intolerance. These products contain added lactase, which facilitates digestion for people with lactose intolerance. 

The difficulty comes mainly from eating out, and lactase supplementation is the ideal solution.


Discover our lactose-free recipes


2. Lactase supplementation

Lactase supplementation is an effective solution for avoiding the symptoms of lactose intolerance. Lactase-based food supplements, such as Lactolérance, have been proving their worth for over 30 years

Two distinct packages are available:

  • Protection Package 45 min/1h (taken on demand) : To be taken just before consuming milk products (Lactolérance 4500 for moderate intolerance and Lactolérance 9000 for severe intolerance).


  • 24-hour protection package (one capsule daily) : Lactolérance 1Day offer a permanent solution for all levels of intolerance.


Discover Lactolerance food supplements


👇 Not sure which package to choose? The Discovery pack is for you! 😉👇


Image redirecting to the lactorélance 1day pack and 9000 pill dispenser product sheet


Lactose intolerance is a common digestive disorder which can have a significant impact on quality of life. However, the with a precise diagnosis and appropriate strategies, it is possible to live comfortably. If you suspect you are lactose intolerant, consult a healthcare professional for a precise diagnosis and support.

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