Lactose and its metabolism – digestion, intolerance and elimination diet [EXPLAINED]

Proven content

Lactose is a sugar that occurs naturally in the milk of all mammals. It is also present in most of the products obtained from this milk. However, statistics show that up to 80% of the population in adulthood does not digest lactose, and thus struggles with lactose intolerance. What exactly is lactose and what is the cause of intolerance to this compound? How is lactose intolerance diagnosed and treated?

What is lactose?

Lactose is in other words milk sugar. The very name of lactose comes from the Latin word “lac”, meaning milk. Lactose is an organic chemical compound with the formula written as follows: C12H22O11. This chemical structure means that lactose is a carbohydrate and is a disaccharide composed of D-galactose and D-glucose.

We found out in 1619 that there was an ingredient in milk called lactose. Italian physician Fabrizio Bartoletti in the subsequent editions of his Encyclopedia hermetico dogmatica described the necessary milk serum. Bartoletti obtained a preparation he called manna, and the weight content of lactose in this preparation was 85%. In 1780, Carl Wilhelm Scheel, a German-Swedish apothecary and chemist, classified this ingredient as sugar. In turn, the isolation of the pure form of lactose and its identification and description took place only in 1893. This was done by Franz von Soxhlet, a German chemist of Belgian origin.

Lactose is the compound that gives milk a sweet taste, although it is also less sweet than glucose or sucrose. Sugar is the main source of carbohydrate in infant nutrition and accounts for 40% of calories from milk. Lactose is a highly soluble compound, supports the absorption of calcium, and as a result of its fermentation, butyric acid is formed, which affects the healthy intestinal microflora and nourishes the intestinal cells at the same time.

If you want to know more about carbohydrates and their sources, read on: Simple and complex carbohydrates. What are they and where can they be found?

Lactose – properties and metabolic transformation

Lactose in chemical terms is a colorless substance with a constant melting point of 225 degrees Celsius. It dissolves well in water, poorly in alcohol and does not dissolve in ether at all. The concentration of lactose in cow’s milk ranges from 4,6 to 4,9%while in human milk from 5,5 to 7,5%.

As already mentioned, lactose is made of glucose and galactose. The digestion of these two components is mediated by lactase. Lactase is an enzymewhich is formed in the brush border of the lining of the small intestine. Glucose and galactose under the influence of lactase undergo intestinal absorption and then they can be used as a source of energy for the functioning of the body.

The highest lactase activity in humans occurs in newborns and infants. Later, the activity of lactase decreases with age, so that in most adults it reaches about 10% of the original activity. Scientific research has shown that it occurs in 17-37% of Poles lactase deficiency. This deficiency can lead to disorders that cause the accumulation of lactose in the gastrointestinal tract, and thus the symptoms of intolerance.

How do I get lactose?

Lactose occurs naturally in the milk of mammals and therefore also in the milk of the mother who is nursing the infant. However, lactose can be obtained from whey during cheese production. Lactose concentrate which is obtained from whey is used to feed pigs.

Lactose is used in many different industries. For example, in the food, pharmaceutical and pyrotechnic industries, it is used as a filler. Pharmacists use lactose as an excipient because it helps to obtain a certain concentration of the active substance. Lactose also works great as a means of protecting powders that are highly moisturized.

Do you want to know the truths and myths about breast milk? Check: Mother’s milk from a pediatrician’s perspective – truths and myths

Lactose intolerance – what is it?

Lactose intolerance is a disorder in which the human body cannot fully break down and absorb lactose. This disorder is associated with the production of an inadequate amount of lactase for the organism. When lactase production is too low, all lactose is transported to the large intestine. Lactose, which goes entirely to the large intestine, is an ideal nutrient for the bacterial flora. Due to the action of the bacterial flora, hydrogen and carbon dioxide as well as short-chain organic acids are released.

Additionally, undigested lactose retains water in the large intestine, which increases the volume of the formed stool. Moreover, the butyric and acetic acids produced during fermentation increase the acidity of the faeces. In the case of lactose intolerance, the characteristic symptoms of this disorder begin to appear already 30 minutes after eating a meal with lactose, i.e. severe abdominal pain, flatulence, smelly gas, nausea and diarrhea.

People who are lactose intolerant may have gluten intolerance. Get tested, choose a mail-order test for lactose and gluten intolerance.

You can also do genetic testing for food intolerance to gluten, lactose and fructose. Thanks to them, it will be easier for you to adjust your diet to avoid unpleasant ailments.

If you want to know more about food intolerance read on: Food intolerance

Types of lactose intolerance

Lactose intolerance can be caused by various factors. Taking them into account, specialists list three basic ones types of lactose intolerance. These types are simultaneously causes of lactose intolerance:

1. congenital lactose intolerance in infants – the so-called alactasia is a disorder that is a very rare form of lactose intolerance. This lactose intolerance is already detected in infancy. Patients diagnosed with primary lactose intolerance are forced to follow the principles of a lactose-free diet throughout their lives; 
2. primary lactose intolerance in adults – that is, hypolactasia, is a disorder that appears and increases with age. In adults, the activity of lactase, which breaks down lactose into glucose and galacatose, decreases with age. These people did not have any childhood problems with digesting lactose. Typically, this type of lactose intolerance is genetically determined (intolerance is inherited as an autosomal recessive trait) and ethnically;
3. secondary lactose intolerance – is a disorder that results from damage to the intestinal epithelium as a result of disease processes. So it means that in this case, lactose intolerance is an acquired disorder. Secondary lactose intolerance can be temporary or permanent. It depends on the type and duration of the effect of the factor that damaged the mucosa of the small intestine. Transient cases usually occur after the use of drugs that can destroy the intestinal mucosa, and therefore primarily antibiotics. Persistent, secondary lactose intolerance, in turn, is a consequence of diseases such as celiac disease, cystic fibrosis, Crohn’s disease, carcinoid, gastrointestinal allergy or giardiasis.

What should you know about Crohn’s disease? Check: Crohn’s disease

How is lactose intolerance manifested?

Symptoms that occur in lactose intolerance are the result of the lack of digestion and intestinal absorption of lactose in the form of glucose and galactose. Undigested lactose accumulates in the lumen of the intestine, where fermentation takes place and gases and acids are produced.

Symptoms of lactose intolerance they are not specific and very often resemble symptoms characteristic of many other gastrointestinal diseases. The symptoms of lactose intolerance are primarily:

1. stomach pain;
2. flatulence and nausea;
3. diarrhea;
4. a feeling of fullness and tension in the abdomen;
5. gas;
6. colic;
7. characteristic “overflow” and audible peristaltic movements of the intestines. 

The symptoms and their severity largely depend on the amount of eaten foods and their lactose content. The rule is simple, the more lactose-containing products we consume, the more severe the symptoms will be. The first symptoms of lactose intolerance may occur as early as 30 minutes after eating lactose-containing foods, and in some cases symptoms appear only a few hours after a meal. In such situations, patients often do not associate the symptoms with the food eaten and do not even suspect that the symptoms may be a symptom of lactose intolerance.

What are the causes of recurring abdominal pain? Check: Stomach pain

What to do in case of lactose intolerance?

If symptoms characteristic of lactose intolerance occur, please consult your doctor. You should never self-diagnose lactose intolerance. At the beginning, it is worth going to a general practitioner who, after a thorough interview and initial examination, will refer you to a specialist.

In the case of lactose intolerance, it is worth using the advice of a dietitian, because the treatment of this ailment is mainly based on an elimination diet. An elimination diet is based on the removal of products that contain lactose from your diet.

Who do you go to for a referral for medical examinations? Check: Referrals for medical examinations

Lactose intolerance – diagnosis

If lactose intolerance is suspected, it is very important to perform appropriate diagnostic tests. The following tests may be ordered by the doctor:

1. hydrogen breath test – also known as the test of the presence of hydrogen, it is a test that allows you to determine whether the process of digestion and absorption of carbohydrates is correct. The hydrogen breathing test consists in collecting samples of the exhaled air in a special device. This device measures the amount of hydrogen in the exhaled air. The study is divided into several stages. The first sample collection is performed on an empty stomach. The patient is then administered a liquid that contains lactose. Subsequent air samples are taken at specified intervals, e.g. every 20 minutes for approx. 3 hours. The number of downloads depends on the laboratory or medical facility where the test is performed. The price of such a test is about PLN 200. What is the interpretation of the results? If the patient is healthy and does not suffer from lactose intolerance, the hydrogen excretion should not exceed 10 ppm. However, subsequent measurements do not show results above 20 ppm;
2. lactose tolerance test – it is a test that consists in several tests of glucose concentration in the blood serum: before consumption of lactose and at specified intervals after its consumption. During the test, blood samples are taken in which the level of glucose is determined; 

We recommend mail-order lactose intolerance testing available on Medonet Market. With it, you will find out if you can eat dairy products without worrying about unpleasant ailments.

1. urine test – urine is tested for the presence of galactose after giving the patient 50 g of lactose with ethanol. A urine sample is collected approximately 40 minutes after the liquid has been consumed. Using the same method, the so-called strip tests. If there is no change in color of the strip, it means lactose intolerance;
2. stool pH test – the stool test measures its pH. An acidic stool pH usually indicates lactose intolerance, as the lactose undigested in the intestines acidifies the stools;
3. elimination test – it is one of the most frequently proposed methods for the diagnosis of lactose intolerance. The elimination test consists in removing all lactose-containing products from the diet. If for two weeks of such a diet the troublesome symptoms disappear, and then return when lactose is included in the menu again, there is a high probability of a diagnosis of lactose intolerance; 
4. genetic tests – is performed by analyzing a blood sample for the presence of polymorphism in the LCT gene on the second chromosome. Lactose intolerance – LCT gene testing can be purchased at Medonet Market. It is a shipment test, so we collect and send the sample to the laboratory by ourselves, and we will get the results after 2-4 weeks;
5. small intestine biopsy – a biopsy may be performed using an endoscope or a Crosby capsule. In the case of endoscopic biopsy, a flexible tube ending with a camera is inserted into the intestine, through which small forceps are inserted, which take a section of the intestinal wall for examination. The procedure is performed under local anesthesia. Using Crosby capsules, a thin probe is inserted into the intestine with a head for taking sections. The capsule is sucked to the intestinal wall and then cuts off a small fragment of the mucosa. Thanks to this method, it is possible to collect slightly larger material for examination, which will provide a better histopathological picture. 

What is worth knowing about the digestive system? Check: Digestive system – the most important information

Lactose intolerance – treatment

Many patients diagnosed with lactose intolerance wonder how to treat this condition. Unfortunately but lactose intolerance is incurable and the only way to reduce its symptoms is to change your diet.

If the tests show unquestionably lactose intolerance, you should decide to plan an elimination diet, i.e. based on lactose-free products. However, this does not mean that you should completely give up dairy products. Small or trace amounts of lactose are found in buttermilk, sour cream, kefir and yoghurts. Long-fermented cheeses, such as Parmesan and other blue cheeses, are also a good choice. There are also special lactose-free products on the market that greatly enrich the diet.

Lactose intolerance can also be treated on an ad hoc basis with appropriate medications. Of course, this still does not mean that you can recover from this ailment. However, if a person with lactose intolerance is going to a wedding, baptism or other larger celebration, where he can expect lactose dishes, he can obtain drug with lactase.

These pills provide the body with an enzyme that the body does not normally produce in adequate levels. Thanks to these tablets, you can eat meals with lactose and not struggle with abdominal pain, diarrhea or flatulence. Lactase tablets should be taken just before eating foods with lactose. Among the drugs with lactase, one can mention Lactocontrol or Delicol.

What medications are helpful to support the gut flora? Check: Prebiotics, probiotics – who need them and should they be taken, what are they in?

Lactose intolerance and sensitization and allergy

Many people confuse lactose intolerance with a milk allergy or a protein flaw. To understand the difference between the two conditions, it is important to understand the mechanisms that are fundamental criteria for the diagnosis of these diseases.

Lactose intolerance is the reduced or inability to break down the disaccharide lactose. Milk protein allergy is one of the most common food allergies. An allergy is an abnormal, immune, overreaction of the immune system against non-pathogenic external factors. Allergic reactions appear from 2 hours to even several days after consuming the allergenic protein.

It is worth remembering that lactose intolerance is manifested mainly by gastrointestinal problems, while allergy or allergy to dairy products may additionally cause a rash or breathing difficulties in the patient. These ailments do not always appear, and allergy symptoms may also only appear within the digestive system.

Moreover, in contrast to these two conditions, diagnosis is very important and helpful. Lactose intolerance is diagnosed primarily by performing a hydrogen breath test, a stool pH test or a genetic test. Dairy allergy, on the other hand, is diagnosed on the basis of skin prick tests, serum IgE levels and challenge tests.

The difference in the time of the body’s reaction and the appearance of the first symptoms after eating a given food is also important. In the case of lactose intolerance, the first symptoms appear 30 minutes to 2 hours after drinking milk or consuming products with lactose. In the case of allergies, however, it is necessary to wait a little longer for the immune system to respond. Symptoms after consuming milk or milk products will not appear earlier than 2 hours after a meal. It is not uncommon for symptoms to take several days to appear.

What is protein diathesis? What are its causes and symptoms? Check: Protein flaw – causes, symptoms, treatment

Products rich in lactose

As already mentioned, the only one a method of combating the symptoms of lactose intolerance is to avoid foods rich in this disaccharide. Which products contain the highest amounts of lactose?

Many people think that in order to eliminate lactose from the diet, it is enough to stop consuming milk and all dairy products. Of course, you have to do this, but it is not a sufficient condition for a proper elimination diet. Lactose is commonly used in food production.

In order to effectively limit lactose consumption, you should carefully read the ingredients of the selected products. Apart from typical dairy products, special care should be taken when purchasing the following products:

1. bread, especially sweet rolls and buns, and toasted bread;
2. various types of sweets and pastries, including decorations for cakes or sweet toppings and sauces,
3. ready meals, including instant soups or powdered sauces;
4. chips and crisps;
5. meat-based preparations, such as: cold cuts, sausages or pates;
6. margarine.

The main sources of lactose are listed in the table below:

Why is calcium so important to our body? Check: Calcium – not only for strong bones and healthy teeth

Products without lactose

In diagnosed lactose intolerance, one should use products that are devoid of this disaccharide. As the table above shows, milk contains a lot of lactose, but during the processing of milk, the amount of sugar in it decreases significantly. For example, yoghurts, buttermilk, and ripened cheeses contain small amounts of lactose and can be included in the diet of people with lactose intolerance to a limited extent.

The good news for people with lactose intolerance is that there are many products on the market today that have been extracted with lactose. Therefore, in many stores you can buy lactose-free milk, lactose-free cheese or other products without lactose.

It is also worth replacing some ingredients with others. For example, cow’s or goat’s milk can be effectively replaced with plant, oat, rice or coconut milk. Also, preparations of plant origin are lactose-free.

What Are The Principles Of A Dairy Free Diet? Check: Dairy-free diet

Elimination diet – how to replace lactose-free products?

However, it should be remembered that any diet in which certain nutrients are eliminated leads to deficiencies. Giving up milk and dairy products often leads to serious deficiencies of calcium and B vitamins. Therefore, you should include in your diet such products that will supplement your diet with these minerals and vitamins.

Diet of people with lactose intolerance should be enriched with vegetable sources of calcium, such as almond, oat or rice drinks. It is worth reaching for green leafy vegetables, such as kale, broccoli, dill or spinach. Hazelnuts, tofu, quinoa, apricots and amaranth are also vegetable and at the same time a rich source of calcium.

The elimination diet of people with lactose intolerance should also include legumes and fresh fruit, because they protect the body against inflammation and at the same time care for the proper intestinal flora.

If you want to know more about the principles of an elimination diet, check out: Elimination diet, i.e. who should and who needs to go gluten-free

The content of the medTvoiLokony website is intended to improve, not replace, the contact between the Website User and their doctor. The website is intended for informational and educational purposes only. Before following the specialist knowledge, in particular medical advice, contained on our Website, you must consult a doctor. The Administrator does not bear any consequences resulting from the use of information contained on the Website. Do you need a medical consultation or an e-prescription? Go to halodoctor.pl, where you will get online help – quickly, safely and without leaving your home.Now you can use e-consultation also free of charge under the National Health Fund.