“Coffee with milk and sugar?”

“Black please, unfortunately I have a milk intolerance!” Who hasn’t heard a colleague, acquaintance or oneself say this in everyday life. People who drink their coffee black or with a milk alternative cannot tolerate the lactose in milk. They are therefore "lactose intolerant".

Lactose refers to a disaccharide, which is commonly known as "milk sugar". In Germany, around 17% of the population suffer from a diagnosed intolerance to this milk sugar, with the number of unreported cases being significantly higher. Depending on the severity of the disease, intolerance to lactose can be felt in the form of bloating, stomach pain and discomfort, as well as abdominal cramping, diarrhoea and vomiting. Those affected also often complain of unspecific symptoms, such as physical exhaustion, fatigue and sleeping disorders. In principle, lactose intolerance can be developed in humans at any stage of life, from birth to death. More frequently, however, the disease occurs only in adolescence. It is possible to return to being lactose-intolerant.

As the term milk sugar already suggests, lactose is mainly contained in dairy products such as cow's milk, cheese and yoghurt. There are also products that may not initially appear to contain lactose but which do contain a small amount. These include, for example, instant soups or even medicines. This leads to the first and most important starting point for the treatment of lactose intolerance: a change of diet. Foods containing lactose should be completely avoided and replaced with other foods, e.g. soya milk or soya yoghurt. Another treatment option is the use of so-called lactase tablets, which allow dairy products to be consumed without a problem.

Lactose – What is it?

Chemically speaking, lactose is a disaccharide consisting of the sugar components glucose and galactose (monosaccharides). Functionally, once the disaccharide has been broken down in the gastrointestinal tract, these components are used for energy production and as a building block for the cell membranes .

Lactose degradation in the gastrointestinal tract

Normally, the milk sugar is broken down in the intestinal mucous membrane by the “lactase” enzyme, since ultimately only the sugar components glucose and galactose can be absorbed and utilised by the body. The enzyme is produced by the mucous cells of the small intestine and is delivered to the digested food as required. If the lactase enzyme comes into contact with the lactose there, the enzyme “snips" the disaccharide into the two simple sugars: galactose and glucose, which can then enter the blood from the intestine. The simple sugars are transported to the target sites in the body through the blood, that is to say to places where the body really needs them for the development and maintenance of vital functions.

Lactose intolerance – What is it?

Lactose intolerance is a general deficiency of the lactase enzyme which means milk sugar cannot be broken down in, the small intestinal mucous membrane, or at best only inadequately. Consequently, the components are not absorbed into the blood via the small intestinal mucous membrane. The lactose migrates as a whole into the colon. Once there, it is used as nourishment for certain intestinal-specific bacteria and broken down. This process, known as fermentation, produces gases such as hydrogen and carbon dioxide. If these are present in larger quantities in the human colon, they lead to the classic symptoms of lactose intolerance in humans: stomach-aches or flatulence. Further degradation products in this bacterial degradation process include substances such as lactic acid and short-chain fatty acids, which ultimately result in water retention and lactose-induced chronic diarrhoea.

Forms of lactose intolerance

Once a person has been diagnosed with lactose intolerance, a distinction is then made between primary, secondary and congenital lactose intolerance. The first and most common form of lactose intolerance worldwide occurs only in childhood and adolescence. The main reason for this is that the effectiveness of the enzyme decreases over the years. Secondary lactose intolerance is the inability of humans to break down the lactose sufficiently in the intestine. In this case, existing diseases of the gastrointestinal tract, side effects from medicines and general nutrient deficiencies are the cause of secondary lactose intolerance. These reduce/prevent sufficient provision of the lactase enzyme as a result of damage to the small intestinal mucous membrane. The lactose absorbed with the food is inadequately digested and leads to the described health problems in the large intestine. Congenital lactose intolerance is a particularly serious form, since a newborn cannot be breastfed with its mother's milk. If a lactose-intolerant infant were breastfed with its mother's milk, the lactose would enter the baby's bloodstream directly and lead to severe symptoms of poisoning.


Typical symptoms that occur from a few minutes to hours after eating dairy products and foods containing lactose are:
  • Bloated stomach
  • Loud bowel noises
  • Flatulence
  • Stomach-aches and stomach cramps
  • Painful bowel movements
  • Nausea and vomiting
  • Diarrhoea
  • Common problems such as headache, fatigue, lethargy and concentration disorders

At the same time, these complaints can also occur in connection with other food intolerances, or even simply as a result of gastrointestinal infections. Therefore, a test should be carried out to clearly identify whether a lactose intolerance is present.

Diagnosis of lactose intolerance

First of all, people who suspect a lactose intolerance in themselves or other individuals should observe the reactions of the body after dairy products are eaten. Do one or more of the typical complaints occur? And if so, how severe is the reaction? Could other foods which were consumed at the same time have led to the complaint? To answer these questions, it is often helpful to keep a nutritional diary. This enables the affected person to individually record when, what and how much was eaten and also whether and to what extent complaints have occurred. A good way of confirming or rejecting the suspicion of lactose intolerance is the H²breath test. You can buy this and other screening tests from Cerascreen® and perform the test from the comfort of your own home, saving time-consuming and nerve-racking visits to the doctor.

H2 Breath Test with the Lactose Test kit from Cerascreen®

The lactose intolerance test kit is available from Cerascreen® for independent and uncomplicated testing for lactose intolerance. The package includes the test most routinely used by doctors and thus the gold standard for testing lactose intolerance: The H2 Breath Test. This is also used in a modified form to test for fructose and sorbitol intolerance (see article on fructose and sorbitol). When lactose intolerance is suspected, and the lactose intolerance test kit is used, the patient drinks milk sugar dissolved in a certain amount of water. The solution must be drunk within four minutes on an empty stomach. In the case of an existing lactose intolerance, the lactose absorbed continues to enter the intestine undigested. Hydrogen is produced, among other things, as a result of the breakdown of the lactose by bacteria. The person exhales this gas, and it can therefore be measured independently by cerascreen or by a doctor. If the value is more than 20 ppm, this is a strong indication that a lactose intolerance is present.

Lactose in food

If a lactose intolerance has been clearly diagnosed, the individual concerned should test which foods should be avoided in the future because of high lactose content and which foods can still be consumed without any problems. The following table provides initial relief from a labyrinth of not always clear and informative websites, books and blogs on the subject. The lactose contents of selected foods are listed here. These are considered as “lactose-free” according to the food regulation if they contain a residual content of less than 0.1g of lactose per 100g of food.

Living with lactose intolerance

Even if lactose intolerance is present, the affected individual should not despair right away: there is neither the risk of a life-threatening condition, nor the risk of reduced life expectancy due to intolerance. If the affected individual generally follows a lactose-free diet or takes lactase tablets, it can be assumed that the individual will continue to cope with normal everyday life with no unpleasant ailments or symptoms.