Lactose intolerance: what are the symptoms? Is there a cure?


What is lactose intolerance?

Lactose intolerance is the inability to completely digest the sugar (lactose) present in dairy products, such as milk and milk products. It happens due to a deficiency in the production of the enzyme lactase , responsible for the synthesis of lactose.

There are various levels of lactose intolerance, causing some people to have more intense symptoms than others. Among the symptoms, the most common are diarrhea, nausea and abdominal cramps.

Unfortunately, the problem has no cure, but the treatments available can help the patient to live better with the condition. The intolerant will usually have to make some changes in the diet, avoiding the consumption of dairy products, or else make use of lactase supplements.

It is estimated that, in Brazil, lactose intolerance affects around 40% of the population, as ethnic factors are involved in the incidence rates of the problem.

Learn more about lactose intolerance in the text below! Good reading!

What is lactose?

Lactose is a carbohydrate (sugar) present in milk. It is, more specifically, a disaccharide formed by the joining of two monosaccharides, glucose and galactose. The word lactose comes from the Latin, where lac  means “milk” and “ose”  means chemistry.

In order for lactose to be absorbed by the body, the action of an enzyme called lactase is necessary. Lactase is an enzyme common to all mammals and, in humans, it is produced in the small intestine.


There are 3 types of lactose intolerance. The symptoms of the three are the same, but they differ from each other by their origin. Check out:

Congenital lactose intolerance

Congenital lactose intolerance occurs when the child is born without the conditions to produce the enzyme lactase. It happens very rarely, being categorized as an autosomal recessive inheritance. This means that both the father and the mother need to transmit the lactose intolerance gene for the child to present the problem.

Primary lactose intolerance

Primary lactose intolerance refers to that which is acquired naturally throughout life by some individuals.

When we are still babies and children, the body still produces enough lactase, since breast milk has been the first source of nutrition since birth. As we age and vary our diet, the production of the enzyme lactase also decreases, which leads to lactose intolerance.

Secondary lactose intolerance

This latter type of lactose intolerance occurs when the large intestine stops producing the normal amount of lactase because of illness, surgery or injury.

In most cases, lactose intolerance disappears when treating the initial condition that causes lactase production deficiency.


Lactose intolerance happens because of a deficiency in the production of lactase, the enzyme produced by the body responsible for breaking lactose into glucose and galactose.

The deficiency in the production of this enzyme causes the presence of lactose in the body through the ingestion of milk and its derivatives, causing symptoms such as nausea and diarrhea.

Congenital lactose intolerance, as stated in the previous topic, is caused by an autosomal recessive inheritance, that is, it is a genetic disease, transmitted from the parents to the child, in which it is necessary that both parents transmit the deficiency gene in the production of lactose so that the child has intolerance.

Primary lactose intolerance occurs naturally in some individuals over the years and as a result of dietary changes, while secondary lactose intolerance is caused by injuries, surgeries or some diseases, such as:

  • Celiac disease;
  • Gastroenteritis;
  • Crohn’s disease.

In most cases of secondary lactose intolerance, the disease cures as soon as the disease causing the deficiency in lactase production is cured.

Risk factors

Although it is possible for anyone to become lactose intolerant, there are some risk factors that increase a person’s chances of developing the problem. Are they:


As we age and change our diet, lactase production decreases, which causes lactose intolerance to arise. For this reason, the problem is much more common in older people.

Genetic factors

Children born to parents with lactose intolerance or who carry the gene that causes the deficiency are more likely to have congenital lactose intolerance.


Lactose intolerance is much greater in people of Asian descent. It is also more common among blacks, Hispanics and indigenous people.

This is because these peoples have not become accustomed, over the generations, to the consumption of milk after childhood. The Nordics, for example, are a people who have been consuming milk and milk products for many generations, which makes the incidence of the disease less.

This low occurrence was due to natural selection. Individuals who lived in cultures where milk and milk products were consumed and did not have lactose intolerance in the past, lived longer than those who had and passed on their genes.

Premature birth

Premature babies, in general, have less lactase in the body, as their body is not yet fully developed.


Some illnesses can cause lactose intolerance. Are they:

Crohn’s disease

The Crohn’s disease is a serious inflammatory disease of the gastrointestinal tract and is predominantly affects the lower part of the small and large intestine. It tends to cause diarrhea, abdominal colic, rectal bleeding and fever .

This inflammation in the intestine caused by the disease can reduce the levels of lactase in the body, causing intolerance to arise.


The gastroenteritis is another disease which causes an acute inflammation in the intestine and that affects the gastrointestinal system as a whole. It is very common that this disease manifests itself during the summer and in people who live in places without water treatment, sewage and piped water.

As with Crohn’s disease, it is inflammation in the intestine that can reduce lactase levels in the body.

Celiac disease

The celiac disease is an autoimmune disease that is related to intolerance to gluten . Its most common symptoms involve diarrhea, vomiting, anemia and intestinal pain. In this disease, an inflammatory condition occurs in the body as a result of an exaggerated reaction of the intestine to gluten.

These inflammatory responses in the body make the intestine more sensitive to other substances, such as lactose, which leads to intolerance.


The main symptoms related to lactose intolerance are very characteristic and start around 30 minutes to 2 hours after eating foods that have lactose in their composition. Check out:

  • Nausea;
  • Asia;
  • Abdominal pain;
  • Intestinal irritation;
  • Diarrhea;
  • Vomiting,
  • Swelling.

The presence of more acidic stools can also make the patient feel anal burning and have diaper rash. Young children and babies who are intolerant often lose weight and also grow more slowly compared to others.

It is worth remembering that there are different degrees of lactose intolerance, therefore, the intensity of symptoms varies greatly from person to person.

How is the diagnosis made?

The first way to diagnose lactose intolerance is through a clinical evaluation. It is a common examination, in which the patient reports the symptoms and suspicion to the doctor. This assessment alone, however, is not sufficient to diagnose the disease.

For this reason, there are 3 other tests that can be done to ascertain the existence of intolerance. Check out:

Lactose intolerance test

This test is offered free of charge by the Unified Health System (SUS). In it, the patient receives a dose of lactose fasting and, after a few hours, blood samples are taken to measure glucose levels.

In patients with intolerance, these levels remain unchanged, since, without the breakdown promoted by lactase, the intestine does not absorb lactose nor transform it into glucose.

Expired hydrogen test

In humans, only bacteria located in the colon are capable of producing hydrogen. They produce this gas when exposed to unabsorbed food, especially sugars and carbohydrates .

A certain amount of the hydrogen produced by these bacteria is absorbed into the bloodstream through its walls and is transported to the lungs, where it is released on the breath, and can be measured.

The person suffering from lactose intolerance exposes these bacteria to lactose, causing it to produce hydrogen within the human body. It is for this reason that the expired hydrogen test can be used to diagnose intolerance.

In the test, the patient must fast for 12 hours. Then he does the test, which consists of blowing slowly into a portable device that measures the initial concentration of hydrogen.

Then, the patient ingests a small amount of lactose and additional samples of exhaled air in the device are analyzed, measuring the levels of exhaled hydrogen. High levels of this gas are indications of intolerance.

Stool acidity test

This test is less used and is performed from the feces recently eliminated by the patient. When a high level of acidity is detected, the chances of the patient having lactose intolerance are great.

Genetic testing

The genetic test for lactose intolerance is the most accurate, as it directly analyzes the patient’s genome to ascertain the existence of some type of intolerance. However, due to its price, it is not as accomplished as the others.

It can be less invasive than the others, when it is done through the oral sample method, in which a simple scraping of the internal part of the mouth is done with a collector. However, it can also be done using blood samples collected.

The main advantage of this method is that it is not necessary to ingest any amount of lactose.

Is lactose intolerance curable?

Lactose intolerance, unfortunately, has no cure . However, there are ways for the patient to avoid the onset of symptoms. One of the things that can be done is the adoption of a more restricted diet in dairy products or the implementation of lactase supplements.

What is the treatment?

Although lactose intolerance has no cure, this does not mean that intolerants cannot consume lactose foods, such as milk and milk products. This is because the lack of lactase in the body can be controlled through the use of some medications and other treatments.

Enzyme supplements

One of the ways to treat intolerance is through enzyme supplements. Once the intolerance is diagnosed, doctors suspend the intake of milk and milk products at first, to promote symptom relief.

Then, these foods are gradually reintroduced into the diet until the maximum amount that the body can handle without having adverse symptoms is identified. Doctors opt for this option to maintain the supply of calcium in the diet, since this nutrient, together with vitamin D, is indispensable for healthy bone formation.

After that, the intolerant can take lactase supplements before meals that involve milks and derivatives, preventing the symptoms of intolerance from reappearing.

Special food

In order not to deprive yourself of all the benefits that milk can bring, special foods, such as low-lactose milk, can be included in the diet so that calcium intake is not compromised.

Probiotics and prebiotics

Probiotics are microorganisms that can provide several health benefits when consumed. Prebiotics, on the other hand, are a type of fiber that act as food for these bacteria.

When probiotics and prebiotics work together, the symptoms of lactose intolerance can be reduced.

Bone broth

Simple and tasty, bone broth is great for treating the gut because it helps to treat intolerances and sensitivities. However, it is important to remember that there is no scientific support for the effectiveness of bone broth to improve symptoms of lactose intolerance.


After lactose intolerance is identified, many patients turn to ingesting exogenous lactase . They are nothing more than the enzyme responsible for breaking down lactose and can help patients consume dairy foods without feeling the side effects.

There are different brands on the market with different amounts of the enzyme, so before taking this medicine, it is very important to talk to your doctor.

In addition, intolerants can benefit greatly from the use of probiotics, because the live or active cultures present in supplements, fermented vegetables and kefir can help stimulate the production of lactase by the body.


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Living together

Living with lactose intolerance is quite annoying, since the patient is unable to eat a series of foods that are often quite tasty.

In addition, there is a lack of understanding on the part of third parties about intolerance. Many think it is “freshness” or that the intolerant is being rude to not accept this or that food.

Other than that, it is possible to live a normal and quite peaceful life. Intolerance does not pose any major complications for those who have it. Even so, it is necessary for the intolerant to make life changes and take some precautions.

The main one involves talking with doctors and nutritionists to come up with a new dietary routine that offers all the nutrients necessary for a healthy life.

For this reason, we have listed foods that should be avoided and others that can bring great benefits to the intolerant. It is worth remembering, first of all, that it is extremely necessary to talk to doctors and nutritionists to arrive at the most suitable diet for you. Check out:

Foods containing lactose

There is a variety of foods that intolerants should avoid. Check it out below:

Dairy products

  • Cow’s milk (all types);
  • Goat milk;
  • Cheeses;
  • Ice cream;
  • Yogurt;
  • Butter.

Other foods

  • Foods made with milky sauce, such as quiche;
  • Cookies and crackers;
  • Chocolate;
  • Cakes;
  • Bakery products;
  • Breads and baked goods;
  • Cakes;
  • Breakfast cereals;
  • Instant soups and sauces;
  • Processed meats, such as ham or pre-cut sausages;
  • Ready meals;
  • Sauces;
  • Desserts and creams.

List of ingredients

An important tip for intolerant people is to check the list of ingredients of the product you are buying, as the above-mentioned foods do not necessarily always have lactose.

Therefore, when looking at the list of ingredients, avoid buying and consuming foods that contain in their formula:

  • Milk;
  • Milk solids;
  • Powdered milk;
  • Serum;
  • Whey protein;
  • Milk casein;
  • Milk sugar;
  • Buttermilk;
  • Born.

Calcium-rich foods

When the degree of intolerance is very high, it is interesting for the patient to try to ingest calcium through other foods. The recommended daily calcium intake is 1000mg per day, so it is worth knowing what these foods are. Check out:

  • Boiled egg: there are about 54mg of calcium in a 100g serving of boiled chicken egg;
  • Broccoli:  in 100g of raw broccoli there are about 400mg of calcium, while the same amount of cooked broccoli counts with 130mg of the substance;
  • Watercress:  100g of watercress has approximately 168mg of calcium;
  • Spinach:  a serving equivalent to 4 tablespoons of cooked spinach contains 160mg of calcium;
  • Cabbage:  2 tablespoons of braised cabbage contains 164mg of calcium;
  • Almonds:  approximately 254mg of calcium is found in 100g of almonds;
  • Açaí:  a small pot with 200g of açaí has ​​approximately 236mg of calcium;
  • Prunes:  100g of prunes have approximately 62mg of calcium.


People with lactose intolerance have a relatively good prognosis. This is because the condition, despite affecting the person’s life in different ways, does not cause major complications.

What happens in most cases is that the patient has to review eating habits and change their diet, since it is better to avoid the symptoms than to expose the body to the discomfort caused by the condition.


The main complication related to lactose intolerance is the possible deficiency in calcium, vitamin D, riboflavin and protein. A poor intake of calcium and vitamin D can lead to bone problems, such as osteoporosis .

These complications, however, are easily overcome by supplementing these nutrients and adopting an alternative diet rich in these nutrients.

How to prevent

Unfortunately, it is not possible to prevent lactose intolerance, as it is closely linked to genetic factors, which are uncontrollable.]

Common questions

Is it bad to use exogenous lactase often?

The constant intake of exogenous lactase does not cause irreversible harm , however, experts recommend that the degree of intolerance of each patient is accurately evaluated, so that an adequate diet is elaborated.

Doctors recommend only using the  industrialized enzyme in cases where the intake of daily dairy products exceeds the daily limit  recommended by the nutritionist.

To put it more simply: if you do not know the amount of lactase naturally produced by your body or what it represents in terms of lactose allowed in the dish, it is easy to miss the dose and eat too much milk for little enzyme.

What is the difference between lactose intolerance and milk allergy?

There are major differences between lactose intolerance and milk allergy , and the two should not be confused.

Intolerance is nothing more than a deficiency in the production of lactase, the enzyme responsible for the breakdown of lactose, which causes symptoms of intestinal irritation, diarrhea and malaise to happen.

On the other hand, allergy is caused by the body’s reaction to casein , the main protein present in milk. When the allergic person ingests cow’s milk, the immune system reacts as if it is being attacked by some foreign microorganism.

In addition to digestive symptoms such as vomiting, cramps, diarrhea, abdominal pain, constipation , blood in the stool and reflux, allergy to milk can also cause:

  • Urticaria;
  • Atopic dermatitis;
  • Asthma;
  • Wheezing;
  • Rhinitis.

Milk allergy is a more serious and more severe condition than intolerance because of the intensity of its symptoms, making the allergic person have to be even more careful.

What is the lactose content in 1 glass of milk?

1 cup of cow’s milk contains approximately 5g of lactose for every 100mL of milk. This goes for the milk of other animals as well. Thus, a glass of milk, the equivalent of more or less 250mL, contains 12.5g of lactose.

Human milk, on the other hand, is even richer in lactose. It contains about 7g of lactose for every 100mL of milk.

Lactose intolerance is a very common problem and, although it brings a series of discomforts and requires drastic changes in habit, it does not cause major complications.

Is that you? Do you have lactose intolerance? How do you live with her? Leave your impressions in the comments below and don’t forget to share the text with friends and family who would like to know more about the problem!