Everything you need to know about Lactose intolerance

What is lactose intolerance?

Lactose intolerance is a common digestive issue where the body fails to produce enough of the lactase enzyme, which is required to break down lactose in the body.

Most mammals are born with the ability to digest lactose, because it is the sugar found in mammalian breast milk.

However, for people who are lactose intolerant, the body produces little to no lactase, meaning that the sugar remains intact and is fermented by bacteria in the colon.

This fermentation process causes unpleasant symptoms such as bloating, flatulence, nausea, vomiting or diarrhea (sometimes followed by constipation).

There is no cure for lactose intolerance, but the symptoms can be managed by adhering to a lactose-free diet.

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What are the symptoms of lactose intolerance?

Some of the most common symptoms of lactose intolerance include:

  • Flatulence
  • Bloating
  • Stomach pain and cramping
  • Stomach rumbling
  • Nausea
  • Vomiting
  • Diarrhea (sometimes followed by constipation)

What are the different types of lactose intolerance?

There are four types of lactose intolerance. They are:

  • Primary lactose intolerance

The most common form of lactose intolerance worldwide caused by genetic factors. It is hereditary, meaning that it can be passed down to children if they receive two copies of the recessive ‘lactase non-persistence’ alleles from their parents.

This is the type of lactose intolerance that we test for at AlphaBiolabs.<

  • Secondary lactose intolerance

Secondary lactose intolerance occurs when there is illness or injury to the gut. People with gastrointestinal illnesses such as celiac disease, IBS, IBD, ulcerative colitis etc. can experience secondary lactose intolerance.

Infection, chemotherapy, and certain antibiotics can also cause this type of lactose intolerance. It will often resolve itself but may be permanent in some people.

  • Developmental lactose intolerance

Often seen in premature babies born before 37 weeks, developmental lactose intolerance occurs when lactase is not yet being produced by the body. It usually resolves itself when the newborn becomes older, and lactase production has begun.

  • Congenital lactose intolerance

The most severe form of lactose intolerance. Babies born with congenital lactose intolerance produce no lactase at all, meaning that it is crucial the baby is diagnosed quickly, so that they can be fed the right foods to develop healthily.

Can you develop lactose intolerance or become lactose intolerant over time?

Lactose intolerance can develop at any time, and at any age. In fact, it is estimated that around 65 per cent of people globally have a reduced ability to digest lactose after infancy.

Most new-born babies are born with the ability to produce the lactase enzyme, which is needed to break down lactose in the body.

However, as you get older, lactase levels can start to decline. This means that you can lose the ability to digest lactose, leading to the uncomfortable symptoms associated with lactose intolerance.

Is lactose intolerance an allergy?

No, lactose intolerance is not an allergy.

An allergy affects the immune system, triggering an autoimmune response from the body. Allergies may be mild, moderate, or severe, depending on the individual. In some cases, they can lead to anaphylaxis.

An intolerance typically only affects the digestive system, and symptoms are not usually as serious.

Lactose intolerance is the body’s inability to break down the sugar lactose. It does not cause your body to have an autoimmune response when you consume lactose.

What conditions can be mistaken for lactose intolerance?

Because the symptoms of lactose intolerance are similar to other digestive disorders, it can be difficult to diagnose without confirmatory medical testing.

For example, people with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) can experience symptoms associated with lactose intolerance, including abdominal cramps, bloating and diarrhea.

Lactose Intolerance vs IBS - What's the Difference?

If you suspect you might have lactose intolerance, it is important to discuss your symptoms with your physician so that you can seek the correct diagnosis and treatment.

What can cause you to become lactose intolerant?

You become lactose intolerant when the small intestine stops making enough of the lactase enzyme: the enzyme needed to break down lactose, which is the sugar found in milk and dairy products.

This affects your ability to digest lactose, leading to uncomfortable symptoms.

In rare instances, people can be born without the ability to produce lactase, making them lactose intolerant from birth. This is called congenital lactose intolerance.

Other forms of lactose intolerance are triggered by medical issues. For example, secondary lactose intolerance usually occurs because of illness or injury to the gut.

The most common form of lactose intolerance worldwide is primary lactose intolerance, which is hereditary and can develop at any age.

It runs in families and causes the amount of lactase a person produces to decrease over time.

This is the type of lactose intolerance that we test for at AlphaBiolabs.

How common is lactose intolerance? How many people have lactose intolerance?

Lactose intolerance is a common condition worldwide and is thought to affect around 40 million Americans, or one-third of the population.

However, it is more common in parts of the world where dairy consumption is low, such as northern parts of China, and some populations in Africa. In these areas, primary lactose intolerance – the most common type of lactose intolerance globally – can be as high as 100%.

Secondary lactose intolerance is the second most common type of lactose intolerance globally. It occurs when there is illness or injury to the gut, but can also develop as a result of other factors including gastrointestinal illnesses such as celiac disease, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), ulcerative colitis etc.

Secondary lactose intolerance can also be triggered by infection, chemotherapy, and antibiotics. Although this form of lactose intolerance usually resolves itself, it can be permanent in some people.

Which foods contain lactose?

Lactose is the sugar found in milk and dairy products such as cheese, yogurt, and ice cream.

However, it is also commonly used as an ingredient in other food products including cereal, bread, bakery items, salad dressings and more.

It can also be found in non-food products such as medicines and supplements.

How can you test for lactose intolerance?

If you are experiencing symptoms that you suspect are due to lactose intolerance, the first step is to discuss your symptoms with your physician, who will be able to offer advice and guidance on testing and treatment.

Testing for lactose intolerance can include:

  • hydrogen breath testing, conducted by measuring the level of hydrogen in your breath over several hours after consuming an oral solution of lactose
  • stool acidity testing, which measures the acidity of your stools (feces), usually after dairy has been consumed
  • genetic testing using a DNA sample

An AlphaBiolabs Genetic Lactose Intolerance Test uses a cheek swab DNA sample to assess the likelihood of a person having primary lactose intolerance.

This type of lactose intolerance is hereditary, making genetic testing a useful tool for determining whether you are likely to have primary lactose intolerance.

You have a higher chance of having primary lactose intolerance if you have a first-degree relative (parent, child, sibling) with the condition.

How do I know if I’m lactose intolerant?

If you are experiencing the symptoms associated with lactose intolerance, it might be time to talk to your physician about the next steps with regards to diagnosis and treatment.<

Common symptoms of lactose intolerance include diarrhea (sometimes followed by constipation), stomach pain and bloating, flatulence, nausea, and vomiting.

The only way to know for sure whether you are lactose intolerant is to get tested. Tests can include genetic testing, which can identify the gene variations commonly found in people with primary lactose intolerance, hydrogen breath testing, and stool acidity testing.


Is there a cure for lactose intolerance? How is lactose intolerance treated?

There is no ‘cure’ for lactose intolerance, but symptoms can be managed by excluding lactose from the diet, taking medication to assist with lactose digestion, or consuming products that have had lactose removed or reduced.

Many people find that they can improve their quality of life by removing foods like milk, cheese, and yogurt from their diet – all of which contain lactose.

However, lactose can also be found in very small quantities in other products such as supplements and medicines, so if you do have a lactose intolerance, it’s important to check labels to ensure that there is no lactose present.

If you are experiencing symptoms of lactose intolerance, discuss these with your physician so that they can determine exactly what should be removed from your diet.

How can I manage lactose intolerance?

Lactose intolerance can be managed by excluding dairy products from your diet.

Although lactose is mainly found in dairy products including milk, cheese, and yogurt, it is also present in some non-food products such as vitamin supplements and medicines.

For this reason, if you are lactose intolerant, it is important that you check labels to ensure that lactose is not present.

It’s also important that you find alternative sources of nutrients that are found in milk such as vitamin B12, riboflavin, calcium, zinc, and magnesium, to prevent any risk of micronutrient deficiencies.

Diet for Lactose Intolerance - Foods to avoid & eat


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Last reviewed: 05/19/2023
Liz Wood AlphaBiolabs

Liz Wood

Health Testing Specialist at at AlphaBiolabs

Liz joined AlphaBiolabs in 2021 as a Health Testing Specialist. As well as overseeing a range of health tests, she is also the lead on several validation projects for the company’s latest health test offerings.

During her time at AlphaBiolabs, Liz has played an active role in the validation of the company’s Genetic Lactose Intolerance Test and Genetic Celiac Disease Test. An advocate for preventative healthcare, Liz’s main scientific interests center around human disease and reproductive health. Her qualifications include a BS in Biology and an MS in Biology of Health and Disease.

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