Lactose Intolerance

Lactose intolerance

When you have lactose intolerance you have a reduced ability to absorb lactose, ie milk sugar from the food. This is because the intestinal mucosa has a lower level of an enzyme, lactate, which is required for the milk sugar to be broken down and taken up by the small intestine. With a lowered level of lactase, milk sugar will instead end up in the large intestine and will be broken down by bacteria, which can cause pain, diarrhea and gas formation.

It is harmless to have lactose intolerance even if the trouble can be perceived as unpleasant. If you avoid eating and drinking foods with a lot of lactose, especially plain milk, you avoid trouble.

The most common form of lactose intolerance is called primary lactose intolerance. Then you have a normal ability to absorb lactose as a child. Then you gradually lose this ability because the lactase decreases and in the end is not enough. This usually happens at the earliest in the teens. Then you usually tolerate foods that contain smaller amounts of milk sugar such as stored cheese, butter and sandwich margarine containing butterfat. Most people also tolerate drinking less milk in conjunction with food. 

Temporary lactose intolerance can be caused if the mucous membrane of the small intestine is damaged by any bowel disease.

Congenital lactose intolerance is a very rare hereditary disease. Children who have congenital lactose intolerance cannot tolerate breast milk or regular breast milk substitutes containing lactose. They, therefore, have serious problems shortly after birth and are often diagnosed within their first weeks of life.

symptoms of Lactose intolerance

It is common to get one

  • gases in the stomach
  • diarrhea
  • gripe
  • swollen stomach.

These symptoms are common and can have many causes other than lactose intolerance.

Treatment of Lactose intolerance

If you have primary lactose intolerance, you will be better off eating foods that contain lesser amounts of lactose.

If you have temporary lactose intolerance, it is important to treat the underlying disease that causes the problems. Once the mucosa has healed, you can eat lactose again.

Sometimes you need extra calcium in the form of a tablet if you do not eat milk products due to lactose intolerance. But that need is more common in cow’s milk protein allergy than in lactose intolerance.

When to seek care?

If you suspect that you have lactose intolerance, you should contact a health care center.

What happens in the body?

What is lactose intolerance?

Lactose intolerance means that the small intestine has a reduced ability to break down lactose into its constituent’s glucose and galactose so that it can be absorbed into the small intestine. The milk sugar instead ends up in the large intestine, where it is eventually broken down by bacteria. Milk sugar draws water which causes diarrhea. When it reaches the large intestine, gases are formed which can be troublesome and sometimes cause pain as the intestine is stretched.

Lactose intolerance is harmless and does not cause sequelae. The trouble can be perceived as unpleasant but can be avoided if you eat less amount of food containing lactose. It is unusual to completely exclude lactose in the diet.

Lactose is broken down in the small intestine

In the small intestine mucosa, there are several different enzymes needed for digestion. They decompose the food so that the nutrients can be sucked up from above all the small intestine and then be carried out into the body. The enzyme that breaks down lactose is called lactase.

If the body lacks or has too little of the enzyme, not all the lactose you get with the food is broken down into the small intestine. It then stays in the intestine and attracts water both in the small intestine and in the large intestine. If too much lactose comes down to the large intestine it can cause diarrhea or loose stools. In the large intestine, the lactose is attacked by gut bacteria and gases are formed.

Three forms of lactose intolerance

There are three different forms of lactose intolerance

  • primary lactose intolerance
  • temporary, so-called secondary, lactose intolerance
  • congenital, so-called congenital, lactose intolerance.

Primary lactose intolerance is most common

Primary lactose intolerance is most common and is due to the body forming less lactase after toddler years. The ability to continue to form the enzyme after infancy varies and is determined by hereditary properties. 

The most common is that the ability to form lactates gradually decreases after the infancy. This is because originally it was not common for people to use cattle milk and lactose-containing dairy products. This is still the case in many parts of the world. Therefore, maintaining lactate levels at a high level after stopping breast milk has not had a survival value for humans.

When humans began using cattle milk, for example, cow’s milk, a genetic change occurred, that is, a hereditary change. It does not reduce the lactase content with age. This had a survival value for men. How common it is to lose or retain its lactase content depends on where in the world you and your ancestors come from. How much of the lactase content you lose varies from individual to individual if you have the hereditary condition to reduce your lactase content and thus the capacity to break down lactose.

The ability you have to break down lactose can reduce a lot without getting any trouble. The decrease can last a lifetime and the ability to break down lactose that you lost cannot be recovered. It does not depend on the diet or whether you eat or refrain from eating lactose-containing products. 

The problems that can be caused by primary lactose intolerance usually come only in the teens, since the reduction of lactase occurs gradually beginning at the earliest after the infancy. Many, probably most, who believe themselves to be lactose intolerant or believe that their children are what it turns out in an investigation do not prove to be it but the trouble has other causes.

Temporary lactose intolerance

Temporary lactose intolerance can be caused if the intestinal mucosa is damaged by any bowel disease. If the mucosa is damaged, it affects the ability to form lactate.

Intestinal diseases can be, for example, untreated gluten intolerance, intestinal inflammation or parasite infections. When the disease is treated and the intestinal injury is healed, lactose is usually tolerated again.

Congenital lactose intolerance

Congenital lactose intolerance is very uncommon and means that the body cannot form lactose. The disease is hereditary and is discovered after birth as soon as the baby starts eating. The child receives water-thin diarrhea when breast-feeding or receiving regular breast milk replacement.

Due to dehydration and weight loss, the condition can quickly become serious, but if you avoid giving the child lactose and give lactose-free breast milk replacement, they will have no trouble. If you have congenital lactose intolerance, you usually have to eat heavily lactose-reduced food throughout your life.

Rarely affects everyday life

Primary lactose intolerance often means that the older the intolerance increases. A few people may eventually have to almost completely stop lactose-containing milk products. However, for most people, it is usually sufficient to reduce the lactose intake slightly by drinking, for example, lactose-reduced milk instead of regular milk. More than that, everyday life is rarely affected.

Symptoms and diagnosis

When the stomach fights

If you think you have lactose intolerance, you should pay attention to the problems you get, when you get them and what you have eaten then. It can help the doctor diagnose. You can also ask close relatives if they have similar problems or if they have bowel disease.

symptoms of lactose intolerance

The most common symptoms of lactose intolerance are

  • gases in the stomach
  • loose stools or diarrhea
  • gripe
  • swollen stomach.

The trouble can come directly or up to a few hours after eating or drinking something containing lactose. The amount of time it takes for the hassles to pass varies from person to person. Of course, it also depends on how much you have eaten in relation to your ability to break down lactose and whether you continue to eat food with lactose.

The symptoms of lactose intolerance are common and can have many different causes. Two examples of diseases that can cause similar problems are IBS and dyspepsia, which means that you have different problems related to the gastrointestinal tract. If you have symptoms from your stomach you should contact a doctor to find out the cause.

Unusual in younger children

Primary lactose intolerance often occurs only in adolescence. It is unusual for children who have not yet reached adolescence to receive lactose intolerance. Therefore, if you notice that a younger child has stomach problems after drinking milk, it is therefore extremely important to contact a doctor to find out the cause.

Allergy to cow’s milk protein can cause more severe problems

Cow’s milk protein is found in all milk products and you can be allergic to the protein both as a child and as an adult.

The symptoms can be similar to those you get from lactose intolerance, but you can also get more severe problems such as vomiting, eczema and respiratory problems.

Since the problems that can be caused by primary lactose intolerance usually come first in their teens, it is more likely that a smaller child is allergic to cow’s milk protein if they suffer from milk and milk products. It should always be investigated so that the child gets the right diagnosis and thus the right dietary treatment. 

exclusion methods

If you have symptoms that may indicate that you have lactose intolerance, you can contact a health care center. There you can get help from a doctor.

You can usually start by completely excluding milk products for four weeks. If the problems disappear then to come back when you start with milk products again you can be either lactose intolerant or allergic to cow’s milk protein.

If you have no problems after a month with a diet that contains a little lactose but normal amounts of milk protein, such as hard cheese, fil, yogurt, and low lactose products, it indicates that you are lactose intolerant.

lactose Load

If the exclusion methods cannot provide a safe answer, you may undergo a so-called lactose load or lactose tolerance test. It is done at a health center or in a hospital.

The study involves drinking a solution containing lactose and then either having to have a blood test or an exhalation test. If you have lactose intolerance, problems such as stomach pain and gases in the stomach should come immediately or within a few hours.

When making a lactose load, do not eat or drink other than water at least ten hours before sampling.

If the test is done with a blood test , you first submit a blood test in the morning. Thereafter, one is allowed to drink a solution containing lactose and then leave blood samples every 15 minutes for one and a half to two hours. The tests show how well lactose is broken down in the small intestine.

Lactose loading can also be done as an exhalation test. Both before and after drinking a lactose solution, the amount of hydrogen in the exhaled air is measured with a special device. If you cannot break down lactose, the amount of hydrogen in the exhaled air increases more than usual after drinking the lactose solution.

Gene tests

You can sometimes also do a gene test with a blood test that you leave at the health center. The test is done if, for example, you have close relatives who have lactose intolerance. It can either confirm or exclude that one has the inheritance which means that over time one loses part of one’s lactase content and thus one’s ability to break down lactose. The test is only useful for some people.

The gene test says nothing about what ability you have to break down lactose at the moment or can be expected to get in the future. Therefore, it does not show whether you have or will get lactose intolerance. But the test response can help the doctor make the right diagnosis if it is weighed against the results of other tests, symptoms and dietary changes.


If the doctor suspects that the inconvenience may be due to some other illness, gastroscopy can sometimes be examined. It is done in hospitals and you should not have eaten or drunk for at least six hours before the examination.

The examination is done so that the doctor brings a thin tube through the mouth down to the stomach and on to the upper part of the small intestine. Through a small camera in the tube, the doctor can look at the intestinal mucosa and take small tissue samples which are then examined under a microscope.

In the samples, sometimes the activity of the lactase can be measured. If the doctor suspects that you have temporary lactose intolerance, the examination can help to determine which disease causes lactose intolerance, for example, gluten intolerance.

It may take time to get the right diagnosis

Sometimes it can take a long time to get the right diagnosis for their stomach problems. Therefore, it is important that you have patience and allow the investigation to take time. The symptoms of lactose intolerance are common and easy to confuse with symptoms of other disorders or diseases. The tests used to determine if you have lactose intolerance can sometimes produce an uncertain result that can be difficult for doctors to interpret.

If the stomach upset comes back after avoiding lactose in the food for a while you should seek care again.

Care and treatment

The problems disappear with a changed diet

If you have primary lactose intolerance you can usually tolerate foods that contain lesser amounts of lactose and the problems usually disappear if you change your diet. Most can withstand a glass of milk for the food. Sometimes, but very rarely, you need to completely avoid eating or drinking food containing lactose in order for the symptoms to disappear. Each individual is allowed to test how much they can withstand. 

If the trouble is due to temporary lactose intolerance, the underlying disease causing the intolerance must be diagnosed and treated. When the disease is treated and the intestinal injury has healed, you can tolerate lactose again.

Congenital lactose intolerance is detected when the baby is newborn and it is then treated by pediatricians and pediatricians. The child first needs to receive a special breast milk substitute that is free of lactose and later lactose-free or heavily lactose-reduced food.

Dietary advice

It is usually possible to eat some ordinary milk products which contain small amounts of lactose without getting any trouble. Stored hard cheese is usually free of lactose. Butter and some table margarine containing butterfat contain very little lactose. Yogurt and file contain about half as much lactose as milk does. It also makes whipped cream and creme fraiche.

Today, there are plenty of so-called low lactose products. It is milk and milk products where the amount of lactose is reduced. They are available for purchase in most grocery stores. There you can also buy oatmeal and soy milk that does not contain lactose.

A dietician or physician can give much good dietary advice, but how much lactose you can tolerate without getting any problems is learned by trying out.

Lactose may exist as a filler in pharmaceuticals, but these are so small that they rarely pose a problem. Read more about additives in medicines.

If you are very lactose intolerant you may need to read the contents declaration even on foods that do not naturally contain lactose.

The enzyme is lactated as drops or tablets

Going to a restaurant or traveling abroad rarely presents any problems, but there can still be times when it can be difficult to avoid lactose. Then there is the opportunity to take lactate as drops or tablets. Lactase can be bought at a pharmacy without a prescription.

Sometimes calcium supplements are needed

Calcium, which is an important component of the skeleton, is largely absorbed by milk and other foods containing lactose. If you do not eat milk products due to lactose intolerance, you may sometimes need extra calcium in your diet. The same can apply to vitamin D. Lactose-free milk, some soy drinks and stored hard cheese contain calcium and vitamin D. 

It is especially important for children and adolescents to get enough calcium and vitamin D for their skeleton to grow and develop. In adults, too little calcium can lead to osteoporosis. Therefore, it is important to eat and drink as many dairy products as you can without it causing any trouble.

In addition to being able to eat hard cheese, there are now more and more low lactose products where you can try out and see what products you can eat and how much you can eat from them without getting any trouble. You should also try to choose products that contain calcium and vitamin D, either naturally or through enrichment.

If you are pregnant or breastfeeding you may need extra calcium supplements.

If you are considering whether you need calcium and / or vitamin D supplements, you should discuss with a dietician, doctor or midwife.

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