What is lactose intolerance

Lactose intolerance is the inability to digest lactose, the main carbohydrate or sugar found in milk, and in dairy products made from milk, including yogurt, ice cream, soft cheeses and butter. The symptoms of lactose intolerance include wind, bloating, abdominal pain or discomfort, nausea and diarrhea. Lactose intolerance is mostly a deficiency, not an absence of the enzyme lactase. These symptoms occur because your body does not fully digest lactose, a type of sugar that is naturally present in milk and other dairy foods. Lactose intolerance is not an allergic reaction and the symptoms are rarely serious.

Lactose intolerance occurs when your body does not produce enough lactase enzyme to break down the lactose in the gut and so the lactose is not absorbed. The unabsorbed lactose moves on to the large intestine where it’s digested by bacteria using their own enzymes producing fatty acids and gases such as carbon dioxide, hydrogen and methane . The gases created in this process can produce the symptoms of lactose intolerance, including bloating, flatulence (wind or farting) and abdominal cramps.

Lactose intolerance can also be caused by some illnesses, such as gastroenteritis (gastro), which temporarily reduce the body’s ability to digest lactose. When this occurs, a low lactose diet may be recommended for a few weeks by your health professional before reintroducing lactose containing foods.

According to the Dietary Guidelines, people with lactose intolerance can tolerate up to 250ml (one glass) of milk each day if it is consumed in small amounts throughout the day and consumed with other foods.

People with lactose intolerance can generally eat cheese, as most types of cheese are very low in lactose. Yogurt is also generally well digested as the bacteria in yogurt helps break down the lactose.

The following table lists the lactose content of various dairy foods.

Table 1. Lactose content of various dairy foods

Dairy food

Lactose content (g)

Parmesan cheese, 40g0
Cheddar cheese, 40g0.04
Swiss style cheese, 40g0.04
Camembert, 40g0.04
Cream cheese, 22g0.55
Cream, 20g (1 tablespoon)0.6
Ice cream, 50g1.65
Ricotta cheese, 120g2.4
Yogurt (natural), 200g10.0*
Regular milk, 250ml15.75

Note: * The lactose content in yogurt decreases each day, even while it sits in the fridge, because its natural bacteria uses lactose for energy.

If you think you or someone in your care might have lactose intolerance, it’s important to see your doctor for a diagnosis and appropriate treatment. As lactose intolerance is sometimes confused with other medical problems, such as irritable bowel syndrome (IBS), it is best to get a proper diagnosis from a health professional. Although self-diagnosis is common, it is not a good idea as it can lead to some people needlessly missing out on the important nutrients provided by milk and other dairy foods.

Dairy foods such as milk, cheese and yogurt are important for good nutrition throughout childhood and adulthood. While milk, cheese and yogurt are an excellent source of calcium they also provide other essential nutrients including potassium, phosphorus, magnesium, protein, vitamin A, riboflavin, vitamin B12 and zinc.

According to the Dietary Guidelines, consumption of milk, cheese and yogurt can help protect against heart disease and stroke, and can help reduce the risk of high blood pressure and some cancers; may reduce the risk of type 2 diabetes; and may contribute to stronger bones.

There’s no cure for lactose intolerance, but most people are able to control their symptoms by making changes to their diet.

Some cases of lactose intolerance, such as those caused by gastroenteritis, are only temporary and will improve within a few days or weeks. Other cases, such as those caused by an inherited genetic fault or a long-term underlying condition, are likely to be lifelong.

Most people with lactose intolerance can manage the condition without having to give up all dairy foods.

The main treatment for lactose intolerance is to reduce the amount of lactose in your diet. That means reducing the amount of dairy products consumed, such as milk, yogurt, ice cream and soft cheeses.

Lactose intolerance is different from milk allergy, which is an immune reaction to milk or milk products that can be serious. An allergic reaction to milk or milk products can cause symptoms such as an itchy skin, rash, swelling of the lips or difficulty breathing. Seek medical advice urgently if you suspect a serious allergic reaction.

When to seek medical advice

The symptoms of lactose intolerance can be similar to several other conditions, so it’s important to see your doctor for a diagnosis before removing milk and dairy products from your diet.

For example, the symptoms above can also be caused by:

  • Irritable bowel syndrome (IBS) – a long-term disorder that affects the digestive system
  • Milk protein intolerance – an adverse reaction to the protein in milk from cows (not the same as a milk allergy)

If your doctor thinks you have lactose intolerance, they may suggest avoiding foods and drinks containing lactose for two weeks to see if your symptoms improve.

Lactose intolerance in children

If your child is lactose intolerant, they may be able to consume small amounts of lactose without experiencing symptoms. This is quite safe, but you may need to experiment to find out how much they can comfortably eat or drink.

If your child is unable to tolerate any lactose, your doctor may refer you to a dietitian for nutritional advice because it’s important for young children to have certain nutrients in their diet to ensure healthy growth and development.

In general, the same rules about foods to try or to avoid are similar for children and adults.

Lactose intolerance in babies

For babies with lactose intolerance, lactose-free formula milk is available to buy from pharmacies and supermarkets. However, soya formula isn’t recommended for children under six months because it contains hormones that may interfere with your baby’s future physical and sexual development.

Breastfed babies may benefit from lactase substitute drops to help their bodies digest the lactose in breast milk.

For many children, lactose intolerance is only temporary and will improve after a few weeks. After this point it’s safe to gradually reintroduce milk and dairy products into their diet.

Advice for breastfeeding women

It’s perfectly safe to breastfeed your child if you’re lactose intolerant. It doesn’t put them at greater risk of becoming lactose intolerant and has important health benefits for your baby.

Benefits of breastfeeding:

  • your breast milk is perfectly designed for your baby
  • breast milk protects your baby from infections and diseases
  • breastfeeding provides health benefits for you
  • breast milk is available for your baby whenever your baby needs it
  • breastfeeding can build a strong emotional bond between you and your baby

Formula milk doesn’t provide the same protection from illness and doesn’t give you any health benefits.

Almost all formula milk is made from cows’ milk. It can contain bacteria, which is why it’s vital to make it up with water hot enough to kill any bacteria ~ 158 ° F (70 °C). It doesn’t protect your baby from infections and diseases like breast milk does.

Health benefits of breastfeeding for your baby

Breastfeeding has long-term benefits for your baby, lasting right into adulthood.

Any amount of breast milk has a positive effect. The longer you breastfeed, the longer the protection lasts and the greater the benefits.

Breastfeeding reduces your baby’s risk of:

  • infections, with fewer visits to hospital as a result
  • diarrhea and vomiting, with fewer visits to hospital as a result
  • sudden infant death syndrome (SIDS)
  • childhood leukemia
  • type 2 diabetes
  • obesity
  • cardiovascular disease in adulthood

Giving nothing but breast milk is recommended for about the first six months (26 weeks) of your baby’s life.

After that, giving your baby breast milk alongside family foods for as long as you and your baby want will help them grow and develop healthily.

Breast milk adapts as your baby grows to meet your baby’s changing needs.

Health benefits of breastfeeding for you

Breastfeeding and making breast milk also has health benefits for you. The more you breastfeed, the greater the benefits.

Breastfeeding lowers your risk of:

What causes lactose intolerance

Lactose intolerance occurs because your body is not producing enough lactase, which is the enzyme that breaks down lactose in the small intestine into two sugars called glucose and galactose, which can be easily absorbed into the bloodstream.

People with lactose intolerance don’t produce enough lactase, so lactose stays in the digestive system where it’s fermented by bacteria. This leads to the production of various gases, which cause the symptoms associated with lactose intolerance.

Depending on the underlying reason why the body isn’t producing enough lactase, lactose intolerance may be temporary or permanent. Most cases that develop in adults are inherited and tend to be lifelong, but cases in young children are often caused by an infection in the digestive system and may only last for a few weeks.

Most people are born with the ability to break down lactose but a range of factors increases the risk of developing lactose intolerance later in life.

The main types of lactase deficiency are outlined below.

Primary lactase deficiency

Genetic factors

Primary lactase deficiency is the most common cause of lactose intolerance worldwide. This type of lactase deficiency is caused by an inherited genetic fault that runs in families.

Some people have lactose intolerance because they have a genetic difference that reduces the effectiveness of their body in being able to break down lactose. The tendency to produce less lactase enzyme with age is more common in people of Asian, African, South American, Southern European and Australian Aboriginal heritage than in people of Northern European descent.

Primary lactase deficiency develops when your lactase production decreases as your diet becomes less reliant on milk and dairy products. This is usually after the age of two, when breastfeeding or bottle-feeding has stopped, although the symptoms may not be noticeable until adulthood.

Congenital lactase deficiency

Congenital lactase deficiency is a rare condition that runs in families and is found in newborn babies.

It’s caused by an inherited genetic fault that means affected babies produce very little or no lactase.

The genetic mutation responsible for congenital lactase deficiency is passed on in an autosomal recessive inheritance pattern. This means both parents must have a copy of the faulty gene to pass on the condition.

Secondary lactase deficiency

Secondary lactase deficiency is a shortage of lactase caused by a problem in your small intestine. It can occur at any age, and may be the result of another condition, surgery to your small intestine, or taking certain medication.

Secondary lactase deficiency is the most common cause of lactose intolerance in the US, particularly in babies and young children.

Possible causes of secondary lactase deficiency include:

  • Damage to the small intestine, such as due to surgery
  • Celiac disease – a bowel condition caused by an adverse reaction to a protein called gluten
  • Crohn’s disease – a long-term condition that causes inflammation of the lining of the digestive system
  • Ulcerative colitis – a long-term condition that affects the large intestine
  • Gastroenteritis, which can strip the intestines of lactase for a week or two
  • Parasitic infection, which can temporarily reduce lactase levels
  • Lack of iron in your diet, which can interfere with lactose digestion and absorption
  • Chemotherapy – a cancer treatment
  • Long courses of antibiotics.

The decrease in the production of lactase in secondary lactase deficiency is sometimes only temporary, but it may be permanent if it’s caused by a long-term condition.

It’s also possible to develop secondary lactase deficiency later in life, even without another condition to trigger it. This is because your body’s production of lactase naturally reduces as you get older.

Developmental lactase deficiency

Some babies born prematurely (before the 37th week of pregnancy) have a temporary lactose intolerance because their small intestine wasn’t fully developed by the time they were born.

This is known as developmental lactase deficiency and it usually improves as affected babies get older.

Risk factors for lactose intolerance

Factors that can make you or your child more prone to lactose intolerance include:

  • Increasing age. Lactose intolerance usually appears in adulthood. The condition is uncommon in babies and young children.
  • Ethnicity. Lactose intolerance is most common in people of African, Asian, Hispanic and American Indian descent.
  • Premature birth. Infants born prematurely may have reduced levels of lactase because the small intestine doesn’t develop lactase-producing cells until late in the third trimester.
  • Diseases affecting the small intestine. Small intestine problems that can cause lactose intolerance include bacterial overgrowth, celiac disease and Crohn’s disease.
  • Certain cancer treatments. If you have received radiation therapy for cancer in your abdomen or have intestinal complications from chemotherapy, you have an increased risk of lactose intolerance.

Lactose intolerance signs and symptoms

The symptoms of lactose intolerance include:

  • flatulence (wind)
  • bloating
  • abdominal pain or discomfort
  • stomach rumbling
  • nausea
  • diarrhea.

The symptoms usually come on 30 minutes to 2 hours after eating or drinking products that contain lactose.

The severity of your symptoms and when they appear depends on the amount of lactose you’ve consumed.

Some people may still be able to drink a small glass of milk without triggering any symptoms, while others may not even be able to have milk in their tea or coffee.


Lactose intolerance diagnosis

It’s important to visit your doctor if you think you or your child may have lactose intolerance, as the symptoms can be similar to other conditions. Before seeing your doctor, keep a diary of what you eat and drink, and what symptoms you experience. Tell your doctor if you notice any patterns, or if there are any foods you seem particularly sensitive to.

Your doctor may suggest trying to remove lactose from your diet for two weeks to see if it helps to relieve your symptoms. Lactose intolerance is usually diagnosed by doing a trial run. If you avoid lactose for a few weeks and your symptoms improve, but when you go back on to lactose your symptoms return, then you probably have lactose intolerance.

Another simple test is to compare whether someone can tolerate lactose-free milk but not ordinary milk.

Other tests that are sometimes done include breath tests and blood glucose tests.

Occasionally, people with severe symptoms, where the diagnosis is not clear, will have a biopsy of their small intestine. In this test, a sample of bowel wall is taken during an endoscopy (when a camera is passed down into the intestines). This is an invasive test and is not commonly used.

Lactose intolerance test

The lactose intolerance test involves giving oral lactose (1.0-1.5g/kg body weight). Lactose intolerance patients develop diarrhea, abdominal bloating and discomfort within 20 to 30 minutes. Blood glucose is measured 60 minutes before the oral lactose is given and 120 minutes after. As a person with lactose intolerance does not digest lactose, the blood glucose level in such a person does not rise more than 20mg/dL above the baseline. This is because your body is unable to break down the lactose into glucose.

Hydrogen breath test

A hydrogen breath test is a simple way of determining if you may be lactose intolerant.

You’ll be asked to avoid eating or drinking during the night before the test. When you arrive for the test, you’ll be asked to blow up a balloon-like bag. This sample of your breath will be tested to find out how much hydrogen is present, measured in parts per million (ppm).

You’ll then be given a drink of lactose solution and your breath will be tested every 15 minutes over the next few hours to see if the level of hydrogen changes.

If your breath contains a large amount of hydrogen (more than 20ppm above your baseline) after consuming the lactose solution, it’s likely that you’re lactose intolerant. This is because lactose intolerance can cause the bacteria in the colon (large intestine) to produce more hydrogen than normal.

Milk tolerance test

In a milk tolerance test, you’ll be given a glass of milk (about 500ml) and your blood sugar levels will be tested. If your blood sugar levels don’t rise after drinking the milk, you may be lactose intolerant.

Stool acidity test

For infants and children who can’t undergo other tests, a stool acidity test may be used. The fermenting of undigested lactose creates lactic acid and other acids that can be detected in a stool sample.

Small bowel biopsy

A small bowel biopsy is rarely used to diagnose lactose intolerance. However, it may be carried out to see if your symptoms are being caused by another condition, such as celiac disease.

In a small bowel biopsy, a sample of your small intestinal lining is taken using an endoscope (a thin, flexible tube with a light and a tiny cutting tool at the end) that’s passed down your throat. This will be carried out under local anesthetic, so it won’t hurt.

The sample of intestinal lining will be tested to see how much lactase it contains. If it only contains a small amount of lactase, it’s likely you’re lactose intolerant. The sample can also be examined to look for signs of possible underlying conditions such as celiac disease.

Lactose intolerance treatment

There’s currently no way to boost your body’s production of lactase. The main treatment for lactose intolerance is to reduce the amount of lactose in your diet. That means reducing the amount of dairy products, such as milk, yogurt, ice cream and soft cheeses, that you eat or changing the way you eat these foods.

Most people with lactose intolerance don’t need to eliminate dairy foods from their diet. Many of these foods don’t contain large amounts of lactose and are a good source of calcium. For example, most cheeses contain virtually no lactose and are usually well tolerated. Yogurt is also generally well digested since it contains bacteria that ferment (or consume) the lactose.

Most people with lactose intolerance can consume around 8-10g of lactose a day without having symptoms. This is the amount present in 175 to 200mL (a small glass) of regular milk.

Tips for people with lactose intolerance

While you don’t need to eliminate lactose from your diet if you are lactose intolerant, you may need to manage how you eat dairy foods to reduce the possibility of symptoms. For example:

  • Drink milk with other foods and not on an empty stomach.
  • Distribute milk intake into small serves spread out over the day.
  • Build up your tolerance by starting small and gradually increasing your milk consumption.
  • Regular fat milk may be better tolerated than low fat or skim milk – fat slows the passage of lactose through your digestive system, giving you more time to digest it.
  • Yogurt is often better tolerated than milk, and cheese is low in lactose and is well tolerated.

Other foods are good sources of calcium:

  • soy, almond and rice milk, although these are often lower in calcium
  • broccoli, tinned salmon, oranges, pinto beans, rhubarb and spinach.

If you suspect you have lactose intolerance, it’s wise to speak to a doctor or a dietitian.

A few people have such severe lactose intolerance that they have to avoid certain medicines because they contain lactose. It’s best to speak with your doctor or pharmacist if this is the case.

Lactose intolerance can be temporary, and it may be possible to gradually reintroduce milk and dairy products over time if you have had to reduce them in your diet.

Lactose intolerance medicine or drops

Over-the-counter tablets or drops containing the lactase enzyme (Dairy Ease, Lactaid, others) may help you digest dairy products. You can take tablets just before a meal or snack. Or the drops can be added to a carton of milk. Not everyone with lactose intolerance is helped by these products.


Probiotics are living organisms present in your intestines that help maintain a healthy digestive system. Probiotics are also available as active or “live” cultures in some yogurts and as supplements in capsule form. They are sometimes used for gastrointestinal conditions, such as diarrhea and irritable bowel syndrome. They may also help your body digest lactose. Probiotics are generally considered safe and may be worth a try if other methods don’t help.

Lactose intolerance diet

In most cases, cutting down on or avoiding sources of lactose and replacing them with lactose-free alternatives is enough to control the symptoms of lactose intolerance.

The exact changes you need to make to your diet depend on how sensitive you are to lactose. Some people are able to tolerate some lactose in their diet without any problems, whereas others experience symptoms after consuming food containing only a tiny amount of lactose.

If you decide to experiment with what you can and can’t eat, make sure to introduce new foods gradually, rather than all at once. This will help you to get used to any foods you might be sensitive to and identify any that cause problems.

Eating fewer products containing lactose, or avoiding them completely, can mean you miss out on certain vitamins and minerals in your diet and increase your risk of complications. You’ll also need to make sure you’re getting enough nutrition from either lacto-free foods or dietary supplements.

If you or your child are extremely sensitive to lactose, talk to your doctor about your diet.

Milk products are rich in calcium needed for healthy bones so you may need to have regular bone density checks.

You may be referred to a dietitian (an expert in diet and nutrition) who can advise you about what foods should be included in your, or your child’s, diet.

Sources of lactose

Some of the main sources of lactose you may need to cut down on or avoid if you’re lactose intolerant are described below.


A major source of lactose is milk, including cow’s milk, goat’s milk and sheep’s milk. Depending on how mild or severe your lactose intolerance is, you may need to change the amount of milk in your diet.

For example:

  • you may be able to have milk in your tea or coffee, but not on your cereal
  • some products containing milk, such as milk chocolate, may still be acceptable in small quantities
  • you may find that drinking milk as part of a meal, rather than on its own, improves how the lactose is absorbed

If even a small amount of milk triggers your symptoms, there are some alternatives you can try, such as soya or rice milk (see below).

Dairy products

Other dairy products made from milk – such as cream, cheese, yoghurt, ice cream and butter – also contain lactose and may need to be avoided if you’re lactose intolerant.

But the level of lactose in these products varies and is sometimes quite low, so you may still be able to have some of them without experiencing any problems.

It’s worth experimenting with different foods to find out if there are any dairy products you can eat because they’re a good source of essential nutrients such as calcium.

Other foods and drinks

As well as milk and dairy products, there are other foods and drinks that can sometimes contain lactose.

These include:

  • salad cream, salad dressing and mayonnaise
  • biscuits
  • chocolate
  • boiled sweets
  • cakes
  • some types of bread and other baked goods
  • some breakfast cereals
  • packets of mixes to make pancakes and biscuits
  • packets of instant potatoes and instant soup
  • some processed meats, such as sliced ham

Check the ingredients of all food and drink products carefully, because milk or lactose are often hidden ingredients.

The lactose found in some foods won’t necessarily be listed separately on the food label, so you need to check the ingredients list for milk, whey, curds and milk products such as cheese, butter and cream.

Some ingredients may sound like they contain lactose when they don’t, such as lactic acid, sodium lactate and cocoa butter. These ingredients don’t need to be avoided if you’re lactose intolerant.


Some prescription medicines, over-the-counter medicines and complementary medicines may contain a small amount of lactose. While this isn’t usually enough to trigger the symptoms of lactose intolerance in most people, it may cause problems if your intolerance is severe or you’re taking several different medicines.

If you need to start taking a new medication, check with your doctor or pharmacist in case it contains lactose.

Lactose-free foods and drinks

There are a number of alternative foods and drinks available in supermarkets to replace the milk and dairy products you need to avoid.

Food and drinks that don’t usually contain lactose include:

  • soya milks, yogurts and some cheeses
  • milks made from rice, oats, almonds, hazelnuts, coconut, quinoa, and potato
  • foods which carry the ‘dairy-free’ or ‘suitable for vegans’ signs
  • carob bars

You can also buy cow’s milk containing additional lactase (the enzyme used to digest lactose). This means you still get the nutritional benefits of the milk, but you’re less likely to experience any symptoms after consuming it.

Getting enough calcium

If you’re unable to eat most dairy products, you may not be getting enough calcium in your daily diet. Calcium has several important functions, including:

  • helping build strong bones and teeth
  • regulating muscle contractions (including heartbeat)
  • ensuring blood clots normally

Therefore, it’s a good idea to choose lactose-free products with added calcium and ensure your diet contains alternative sources of calcium, such as:

  • green leafy vegetables, such as spinach, kale, broccoli, cabbage and okra
  • soya beans
  • tofu
  • nuts
  • bread and anything made with fortified flour
  • fish containing edible bones (for example, sardines, salmon, and pilchards)

You can also buy combined calcium and vitamin D supplements from most pharmacists to help maintain good bone health.

It’s important to check with your doctor or dietitian whether you should be taking supplements, however, as taking excessively high levels of calcium can cause side effects.

Lactase substitutes

In addition to dietary changes, you may also find it useful to take liquid drops, tablets or capsules that contain lactase substitutes. These are available from most health foods shops.

Lactase substitutes replace the lactase your small intestine isn’t producing, which can reduce your symptoms by helping your body break down any lactose in your diet more easily.

Lactase substitutes can either be added to milk or taken just before eating a meal containing lactose.

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