What Is Lactose Intolerance?

  • 1st Revision: Piyumanga Karunaratne

Do you love milk or milk products? Everyone says they are a rich source of calcium and so they must be consumed regularly. But whenever you consume them, you start feeling nauseous. Chances are you are not the only one in the family or your friend circle facing these troubles. You come to know it's lactose intolerance. So, now you are determined to find out more about it and keep your troubles at bay. You have come to the right place as this article will answer all your queries like what is lactose intolerance, its symptoms, and how to manage lactose intolerance.

Lactose intolerance can be irritating but thankfully it is not a life-threatening condition. Small adjustments in lifestyle and dietary habits can keep you healthy and happy.


Lactose intolerance is also called lactose malabsorption. The human body has an organ named the small intestine. It is a part of the gastrointestinal tract. When we eat or drink something, it reaches the small intestine for the digestion process. The food is broken down and the nutrients are absorbed here. Most of the digestion process happens in the small intestine. After that, it passes the waste to the large intestine. 

Lactase is an enzyme found in the small intestine. It is also called lactase-phlorizin hydrolase. This enzyme helps in breaking down lactose obtained from dairy products into glucose and galactose. Individuals who have very low levels of enzyme lactase are not able to digest dairy or milk products. 

As per UK statistics, Asian and African-Caribbean people are mostly found to be lactose intolerant. It can happen to people of any age and it is mostly genetic.

Lactose intolerance should not be confused with milk allergy.¹ Milk allergy is not as common as lactose intolerance. Milk allergy happens due to allergic reactions to milk proteins such as casein. Lactose-intolerant people can tolerate little amounts of dairy products, but people with milk allergy cannot tolerate even a little bit of milk products. They might start experiencing symptoms such as hives, rashes, coughing, or even anaphylaxis. Anaphylaxis is a sudden and life-threatening reaction to some allergic products.

Causes of lactose intolerance 

There are several causes and types of lactose intolerance. There are three types of lactose intolerance:²

  1. Primary lactose intolerance: This is the most common type of lactose intolerance. This mostly starts early in life. When children start weaning (transition from milk to semi-solids), the level of lactase enzyme drops. Some decrease in the enzyme level is acceptable as the body can still digest the milk products. But, sometimes there is a sharp drop in the enzyme level. This can start creating troubles for the child. It can be there till adulthood
  2. Secondary lactose intolerance: Sometimes the body goes through some illness, exposure to antibiotics for a long duration of time, chemotherapy, radiation therapy, or surgery which can lead to a decrease in the lactase enzyme levels. This is often temporary and can be reversed by proper nutrition and care. Conditions such as celiac disease, Crohn's disease, intestinal infection, or gastroenteritis can cause secondary lactose intolerance
  3. Congenital lactose intolerance: It is also called developmental lactose intolerance. It is a rare genetic disorder. In this, the infant is born with lactase deficiency. This disorder is passed from the parents to the child. Premature babies are also at risk of lactase deficiency. These babies cannot consume breast milk or regular formula milk. They need special lactose-free formula milk

Signs and symptoms of lactose intolerance 

There are various symptoms of lactose intolerance. Symptoms might vary depending on the quantity of intake of milk products and start between 30 minutes to two hours. They are 

  • Nausea 
  • Vomiting 
  • Diarrhea 
  • Stomach pain 
  • Bloating 
  • Flatulence

Foods containing lactose 

Lactose is found in milk or milk products (dairy products) obtained from cow's milk, goat’s milk, or sheep’s milk. It is not only limited to dairy products but can also be found in certain processed foods which might use any milk products in the process. These are the various food products with lactose.³

  • Milk 
  • Butter 
  • Cheese 
  • Paneer
  • Cream 
  • Yogurt 
  • Ice cream 
  • Cereals 
  • Sauces 
  • Salad dressings 
  • Protein shakes 
  • Bread 
  • Cake 
  • Pastry 
  • Biscuits 
  • Soups 
  • Margarine 

Management and treatment of lactose intolerance 

If you or anyone in your family have symptoms of lactose intolerance, please consult your healthcare provider. They might need to confirm it through some tests and then they might be able to give you treatment options. Various tests to confirm lactose intolerance are:

  1. Lactose tolerance test: This test will check the absorption of lactose. The patient needs overnight fasting or 8 hours of fasting. At the hospital or clinic, a liquid containing lactose will be given to drink.  Blood samples will be collected over 2 hours. Blood glucose levels will be checked. No rise in blood glucose levels might indicate lactose intolerance, as the usual breakdown of lactose into glucose and galactose cannot happen due to lactase deficiency
  2. Hydrogen breath test: In this too, the patient will be asked to consume a lactose drink. Instead of taking blood samples, the breath will be analyzed several times for hydrogen. High levels of hydrogen indicate lactose intolerance. If there is no or less absorption of lactose, then the amount of hydrogen is high
  3. Stool acidity test: This test is performed for infants and young kids. Stool samples are collected and measured for lactic acid, glucose, and other fatty acids
  4. Genetic testing: As the name suggests, this test uses genes to test for lactose intolerance. There are certain genes commonly found in lactose-intolerant people. So the presence of these genes can be a positive indication. But this test is not that advanced and helpful as much research has not been done yet

Now that we have discussed the diagnosis, let's discuss the treatment options. Though it is not life-threatening, it makes life a bit difficult. So, several dietary changes might help in easing lactose intolerance symptoms.⁴ 

  • Observation: Start inculcating milk and milk products slowly into your diet. Consume a small quantity at a time and observe the reactions it has on your body. It might be a good idea to keep a log of the quantity, product, and its reaction on the body
  • Specific products: There are special lactose-free or low-lactose milk and milk products in the market. These products have lactase enzymes added to them to help the lactose-intolerant. Greek yogurt or cheddar cheese is found to be better for lactose-intolerant people. Though it might vary according to product brand and individuals too
  • Complement with other foods: Some people notice that if they consume milk or milk products with other foods, the symptoms are less. Try milk with cereals or cheese with crackers
  • Lactase enzymes: Lactose intolerance is due to lactase deficiency, so it might be good to start consuming lactase pills or liquid. These can be consumed with meals and they are available over the counter without prescriptions
  • Supplements: Dairy products are a rich source of calcium and other essential nutrients which are required for healthy growth. Children often need more calcium as their bones are still growing. So lactose intolerant kids might get calcium deficiency
  • Try different foods: As we know that calcium and vitamin D  are essential for the healthy development of teeth and bones. But lactose intolerant people might not be able to consume dairy products. So, try different calcium-rich foods such as broccoli, spinach, beans, or sardines


How common is lactose intolerance 

As per estimates, almost 65-70% of the world population is lactose intolerant.¹ It varies as per ethnicity. As per Cleveland Clinic, the estimate is 68% of the world’s population.³ 

Who are at risk of lactose intolerance 

According to statistics, approximately 5% of North Europeans and 90% of East Asians have lactose intolerance.¹ Asian, Hispanic, or African population is more prone to lactose intolerance.

How is lactose intolerance diagnosed 

Lactose intolerance is diagnosed by lactose intolerance test, hydrogen breath test, stool acidity test, or genetic testing.

How can I prevent lactose intolerance 

There is not much research to define how to prevent lactose intolerance. But lactose intolerant people can prevent the symptoms by consuming lactose products in less quantity or avoiding it altogether. 

When should I see a doctor 

You should contact your GP if your symptoms keep coming back, changes in stools like blood in stools or loose stools for 3 weeks, bloating or discomfort for 3 weeks, or weight loss.


If you or your loved one has lactose intolerance, there are various alternatives to milk or milk products available in supermarkets. So, you don't have to completely let go of the milk products from your life. It is always a good idea to consult your GP and your dietitian as they can give you a meal plan and alternatives as per your condition. Some other medical conditions might have similar symptoms, so it is very important to get it ruled out by your GP. Lactose intolerance should not be confused with milk allergy as it is caused by the presence of undigested lactose in the body, which is due to lactase deficiency. You might get confused between different allergies and intolerances, so let's discuss them in brief.⁵

Irritable Bowel Syndrome (IBS): As the name suggests, it affects the digestive system. The exact cause of IBS is not known yet. But experts suggest that food passing either fast or slow through the gut, stress, or family history might be a reason behind IBS. It causes stomach cramps, diarrhea, bloating, and constipation. The symptoms might last for days or weeks. Dietary changes and medications can help ease the symptoms.

Milk intolerance: It is caused by a reaction to the protein in the milk from the immune system, specifically the food-specific IgG antibodies. Symptoms begin between 2 - 72 hours of milk consumption. Around 45% of the UK population is affected by this condition. Fortunately, it is not life-threatening.

Milk allergy: It is caused due to a reaction to the protein in the milk from the food-specific IgE antibody. It affects around 2% of the adult UK population. Symptoms appear within 2 hours of exposure. Symptoms can be fatal, so precautions need to be taken. All milk products should be avoided.

Hopefully, all the confusion about intolerance and allergy is clear now. If lactose intolerance is not letting you consume milk products and you do not try a variety of foods, then you can face severe health issues. As you know, milk products are a rich source of calcium, Vitamin A, Vitamin B1, Vitamin D, and several other essential nutrients. So, improper care in lactose intolerant individuals can cause these issues.⁶

Osteopenia: It is the initial stage of osteoporosis. Scans might show lower bone density and it can be a sign to keep diet and lifestyle in check. If proper care is taken, osteoporosis can be prevented.

Osteoporosis: It is a medical condition in which bones become fragile that they can break easily. It is a slow process developing over the years. It is not a painful condition in itself but the fractures due to it can be painful. A healthy diet and lifestyle can reduce the risk of developing osteoporosis.

Malnutrition: This occurs due to the deficiency of essential vitamins and minerals in the body. Lactose intolerance might lead to malnutrition if proper care is not taken.

Dehydration : This might occur in infants who are dependent on breast milk or formula milk. Parents should keep an eye on symptoms and contact their healthcare provider.


  1. GIS. What is lactose intolerance? [Internet]. Gastrointestinal Society. [cited 2023 Jan 21]. Available from: https://badgut.org/information-centre/a-z-digestive-topics/lactose-intolerance/
  2. Lactose intolerance - Symptoms and causes [Internet]. Mayo Clinic. [cited 2023 Jan 21]. Available from: https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232
  3. Lactose intolerance: symptoms, diagnosis & treatments [Internet]. Cleveland Clinic. [cited 2023 Jan 21]. Available from: https://my.clevelandclinic.org/health/diseases/7317-lactose-intolerance
  4. Lactose intolerance [Internet]. [cited 2023 Jan 21]. Available from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/lactose-intolerance
  5. Test Y. Milk allergy vs milk intolerance [Internet]. YorkTest. 2014 [cited 2023 Jan 22]. Available from: https://www.yorktest.com/advice/milk-allergy-or-milk-intolerance/
  6. Lactose intolerance symptoms and treatments [Internet]. [cited 2023 Jan 23]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/nutritional/lactose-intolerance
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Simmi Anand

B.Sc. Nuclear Medicine, Manipal University
MBA Healthcare Services, Sikkim Manipal University

An experienced Nuclear Medicine professional with a passion for writing.

She is experienced in dealing with patients suffering from different ailments, mostly cancer.

Simmi took a career break to raise her daughter with undivided attention.

During this time, she fine-tuned her writing skills and started writing stories for her child. Today, Simmi is a published author of 'Story time with proverbs' series for young ones. She also enjoys writing parenting blogs on her website www.simmianand.com.

Simmi hopes to reignite her career as a medical writer, combining her medical knowledge with her zeal for writing to produce informative health articles for her readers.

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