Lactose Intolerance 101 – Everything You Need To Know

 by Dr. Steve Hruby, D.C.
Reviewed by Dr. Steve Hruby, D.C.

SuperHumans are the toughest, fittest, healthiest and happiest human beings on this planet. My mission is to help you realize your superhuman potential and learn how to live a long, happy and healthy life.

  Fact Checked
 by Rhealyn Tropia, RMT
Reviewed by Rhealyn Tropia, RMT

I’m a content organizer, fact-checker and super mom who ensures content is medically-reviewed, highly accurate, and engaging. My passion is organizing information and ensuring the facts are presented in a manner that is interesting and easy to understand.

lactose intolerance

Lactose intolerance is among the most common types of food intolerance and affects about 36% of Americans. This condition is caused due to the inability of the body to break down lactose.

Lactose is the sugar found predominantly in milk and other dairy products. Due to the indigestion of lactose, people with lactose intolerance suffer from digestive symptoms such as gas, diarrhea, and bloating.

Although lactose intolerance isn’t a life-threatening condition, it causes discomfort and sometimes embarrassment due to flatulence and other unpleasant symptoms.

Lactose intolerance is most likely hereditary and affects adults and children both. It’s common among Asian Americans, Mexican Americans, American Indians, and African American communities.

Lactose intolerance can’t be treated completely, but by making some dietary changes and taking supplements, the discomforting symptoms can be effectively managed.

Lactose Intolerance: What Is It?

Lactose intolerance, or malabsorption, is a digestive disorder in which the body isn’t able to digest a type of natural sugar called lactose. Lactose is the main carbohydrate found in milk and other dairy products.

This condition is mainly caused by a deficiency of the lactase enzyme in the body. This enzyme is produced in the small intestine and is responsible for breaking down lactose so that the body can absorb and utilize it.

When a person doesn’t have enough lactase to digest lactose in the body, they’re called lactose intolerant.

When this lactose remains undigested and sits in the gut, it causes gas, bloating, and diarrhea.

So, how to tell if you’re lactose intolerant? Here are the most common signs and symptoms of lactose intolerance. If you experience these symptoms after consuming dairy, you’re most likely lactose intolerant.

Signs and Symptoms

These symptoms often appear between 30 minutes to 2 hours after taking lactose.

  • Gas
  • Nausea
  • Bloating
  • Diarrhea
  • Constipation
  • Lower belly pain
  • Abdominal cramps

Lactose intolerance symptoms can vary from person to person. The severity of the symptoms also depends on the amount of lactose consumed and the amount of lactase produced inside the body.

Sometimes the symptoms of lactose intolerance get worse if neglected or remain unnoticed for a long time. 

Want to know How long do lactose intolerance symptoms last?

Related:  Can milk cause acid reflux

Causes Of Lactose Intolerance

If you’re wondering what causes lactose intolerance? Then here’s the answer:

woman in bed suffering from stomach pain

Insufficient Lactase Enzyme Production

The only reason for lactose intolerance is the small intestine’s lack of lactase enzyme production. Lactose, also called “milk sugar,” is composed of galactose and glucose, which are simple sugars. Our body needs lactase in order to break down these simple sugars and use them as energy.

In the absence of this enzyme, lactose, when consumed via dairy products, remains undigested in the gut. When this undigested lactose sits in the gut, the gut bacteria start to break it down, which causes symptoms such as gas, stomach cramps, bloating, diarrhea, etc.

Though a lack of lactase enzyme is the only cause of lactose intolerance, lactase deficiency can be caused by a variety of reasons.

Crohn’s disease, celiac disease, and ulcerative colitis are some digestive conditions that can affect the body’s ability to produce lactase. Besides this, intestinal infections and injuries to the small intestine caused by chemotherapy, trauma, surgery, radiation therapy, etc., can also reduce the lactase production.

Lactose intolerance can be temporary or permanent, depending on the cause of lactase deficiency. For example, if a lactase shortage in the body is due to an injury to the intestine, the problem may be solved automatically after the injury is healed.

Types of Lactose Intolerance

Primary Lactose Intolerance

This type of lactose intolerance is the most common and is caused by aging. When the production of the lactase enzyme in the body is reduced due to aging, it’s called primary lactose intolerance. This type of lactose intolerance is usually acquired through genetics because it’s more commonly found in some populations in comparison to others.

Studies suggest that around 80-90% of Asian and African, 50% of the Middle East and Latin, and under 10% of the Northern European population are affected by primary lactose intolerance.

Secondary Lactose Intolerance

This form of lactose intolerance is caused as a result of any other underlying health condition that affects the small intestine (the origin of lactase). Diseases such as Crohn’s disease, ulcerative colitis, celiac disease, or even chemotherapy or aging could be the factors contributing to the hindered functioning of the small intestine. The inflammation caused in the gut wall due to any such health condition could lead to a temporary halt in the production of lactase.

Congenital Lactose Intolerance

Congenital lactose intolerance is one that’s found in newborn babies. This is a rare condition, as infants aren’t typically lactose intolerant. Babies are often born with lactase enzymes in their intestines. Lactose intolerance generally starts showing up after age three in full-term children.

Congenital lactose intolerance is hereditary and is caused only when both parents possess a particular gene mutation. Congenitally lactose intolerant infants are unable to digest the lactose in breast milk. Thus, this condition could also prove fatal if left untreated or unnoticed. This type of lactose intolerance is lifelong and includes side effects such as high levels of calcium and severe diarrhea.

Developmental Lactose Intolerance

Babies who are born before their digestive systems are fully developed suffer from this type of lactose intolerance. Developmental lactose intolerance is common in premature babies and resolves eventually as the babies grow. But the infant may need to be fed lactose-free formula in place of breast milk after birth.

mother carrying infant behind milk bottles and pump un the table

Tests and Diagnosis

Here’s how to tell if you’re lactose intolerant or how lactase deficiency is diagnosed. Well, for that, tests are required.

You can even do testing for lactose intolerance at home. There’s also an “Am I lactose intolerant quiz” that can help clear your doubts. But in order to be 100% sure, a medical test by a health care professional is recommended.

A medical professional can employ several types of tests and diagnostic methods to determine whether or not one has lactose intolerance. This includes:

Lactose Intolerance Test

In this test, your blood sugar is measured after lactose ingestion. If you aren’t lactose intolerant, your blood sugar levels would be affected as your body processes and utilize the milk sugar. On the contrary, if you’re lactose intolerant, your blood sugar levels would remain the same because your body wouldn’t be able to digest lactose, and it won’t reach the bloodstream. In this scenario, the lactose would directly go to the colon undigested because your body lack lactase.

Hydrogen Breath Test

As the name suggests, the hydrogen in your breath is measured in the hydrogen breath test. A high amount of hydrogen in the breath shows digestive issues that might be related to lactose intolerance. 

Stool Acidity Test

The test is often used to check lactose intolerance in infants and babies. The stool acidity test measures the stool acid levels of the babies. A lower pH suggests lactose intolerance.

Genetic Test

In this test, the genetic causes of lactose intolerance are checked. But one drawback of a genetic test is that individuals with secondary lactose intolerance might receive a false negative.

Lactase Activity At The Jejunal Brush Border

This lactose intolerance diagnosis requires a biopsy of the jejunal brush border, a part of the small intestine. This is an effective way to determine lactase activity, but it’s expensive and invasive.

Treatment and Management

It’s important to note that lactose intolerance isn’t a fatal disease but more of a medical condition. Thus, it can’t be treated, but the symptoms could be managed by making lifestyle changes, as mentioned below.

beans scattered on wooden table near milk in a bowl

Before that, some lactose intolerance home remedies could also help deal with the condition.

Maintain a Healthy Diet

Make sure to include and consume enough calcium. Calcium can also be found in a variety of other foods, including milk alternatives such as soy milk, almond milk, rice milk, etc.

This is because it’s crucial to provide your body with key nutrients found in milk. When you’re on a dairy-limited diet, it becomes vital to find an alternative source of essential nutrients like calcium for the body’s healthy functioning.

Create Your Personal Meal Plan

Here is a lactose-intolerant diet plan to help you make the dietary changes required to deal with the condition.

You can also talk to your healthcare provider or dietitian to make a diet plan that helps you manage the troublesome symptoms of lactose intolerance. But as a thumb rule, you should:

Limit Your Dairy Intake


You can also take enzyme supplements that can help your body digest lactose. In addition, you can also take some digestive health supplements (like probiotic or prebiotic supplements) that can support your gut health and ease digestive symptoms related to lactose intolerance.

Some examples include:

Frequently Asked Questions About Lactose Intolerance

What Diseases Can Lactose Intolerance Cause?

Lactose intolerance is a digestive disorder that can’t cause any diseases but only some unpleasant symptoms.

woman in black cropped top with hands on her belly

Lactose intolerance is when the body can’t effectively digest the lactose in milk and other dairy products. This commonly causes digestive symptoms such as gas, bloating, constipation, or diarrhea. Sometimes the symptoms can be a bit more severe for some depending upon the degree of lactase enzyme deficiency but are generally harmless.

What Can Be Mistaken for Lactose Intolerance?

Digestive disorders such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and sometimes even celiac disease and Crohn’s disease can be mistaken for lactose intolerance. This is because the symptoms of these digestive disorders resemble the symptoms of lactose intolerance.

Here is Lactose intolerance vs celiac disease differentiation to help you figure out whether your symptoms are caused due to former or the latter.

Also, checking out the difference between milk allergy and lactose intolerance before you hop on to a lactose-intolerant diet is important.

Why Is Lactose-free Milk More Expensive?

Lactose-free milk is more expensive than normal milk because of its complicated manufacturing process. Compared to normal milk, lactose-free milk is treated at an ultra-high temperature, making pasteurization even more complex. Besides this, lactose-free milk contains lactase, the enzyme required to break down lactose. The lactase added to the milk is harvested from yeast and mold, making the manufacturing process complicated and expensive.

Other factors contributing to the economic aspect of lactose milk are- an added step in the manufacturing process, low demand, and economies of scale.

Related: Does lactose-free milk taste different


We hope we have addressed all your queries relating to how lactose intolerance work.

Now, if you’re experiencing the common symptoms of lactose intolerance after eating dairy, it’s time to diagnose your condition. Once it’s confirmed that you have lactose intolerance, it will be easier to manage the symptoms.

Just by making some easy dietary changes, you will be able to feel relief and keep up with your day-to-day life. Besides this, you can include lactase or prebiotic/prebiotic supplements to support your gut and overall digestive health.

Furthermore, if required, you can also take the help of a dietitian and get a personalized diet plan that helps you alleviate your symptoms and deal with lactose intolerance.

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