What is lactose intolerance? Causes, symptoms, and treatments

What is lactose intolerance? | Causes | Symptoms | Treatments | When to call a doctor

If you’ve ever had an upset stomach after drinking milk or eating ice cream, you may be lactose intolerant. Lactose is a sugar found in milk and other dairy products. Research suggests that around two-thirds of the global population is affected by some form of lactose intolerance. Here’s what that means for you.

What is lactose?

Lactose is a sugar molecule found in dairy products. Specifically, it is a disaccharide (double sugar) that the body breaks down into the simple sugars glucose and galactose. The body uses these sugars for energy and different functions, such as repairing cells, building muscles, and fueling everyday activities. Lactose makes up 2% to 8% of milk—and is even found as an inactive ingredient in some medications. 

What is lactose intolerance?

Lactose intolerance (also called lactose malabsorption) is the inability to digest lactose. Normally, an enzyme called lactase in the small intestine helps break down lactose so it can be absorbed. People with lactose intolerance don’t have enough lactase, which leads to lactose remaining unabsorbed. The unabsorbed lactose moves on to the large intestine where it is fermented by bacteria, often causing an upset stomach and other digestive symptoms. 

Some groups of people may be more prone to developing lactose intolerance than others. Risk factors for developing lactose intolerance include being of African American, American Indian, Asian, or Hispanic descent; being older; or being born prematurely.  

Causes of lactose intolerance

Lactose intolerance is a chronic condition that can develop at any age due to a number of causes. These causes are divided into four different categories.

Primary

Primary lactose intolerance, also known as lactase nonpersistence, is the most common form of lactose intolerance. It is characterized by a decrease in lactase activity as a person gets older. Primary lactose intolerance usually develops in adolescence and early adulthood.   

Secondary

Secondary lactose intolerance is caused by medical conditions or diseases that damage the intestinal lining. Certain infections and inflammatory diseases can injure the intestinal lining where lactase is normally made, leading to decreased production of lactase. These infections and diseases include celiac disease, ulcerative colitis, and Crohn’s disease. 

Congenital

Congenital lactose intolerance is caused by an inheritance of an autosomal recessive disorder. This type of lactose intolerance is rare and develops at birth. Studies suggest that mutations in the LCT gene are responsible for this type of lactose intolerance. 

Developmental

Developmental lactose intolerance occurs due to an underdeveloped small intestine in premature infants. This type of lactose intolerance occurs in babies that are born at 28 to 37 weeks. However, the baby’s small intestine grows and develops over time to resolve the issue. 

The two main types of lactose intolerance are primary and secondary lactose deficiency. Primary lactose intolerance is much more common than secondary lactose intolerance. In North America, 79% of Native Americans, 75% of African Americans, 51% of Hispanics, and 21% of Caucasians have primary lactose intolerance.   

Symptoms of lactose intolerance

Signs of lactose intolerance are easily recognizable. If you’ve just eaten dairy products and have any of the following symptoms within 30 minutes to two hours after eating, you may be lactose intolerant.    

1. Bloating
2. Flatulence
3. Diarrhea 
4. Nausea
5. Vomiting  
6. Abdominal cramping
7. Indigestion
8. Belching 

These symptoms all happen because the small intestine can’t properly digest the sugar in dairy products. As a result, bacteria in the large intestine ferment the undigested lactose, causing a buildup of gas and water. Adults and children will experience many of the same symptoms if they’re lactose intolerant. 

Lactose intolerance is a manageable condition that does not usually cause serious symptoms. Some people with lactose intolerance don’t experience any symptoms at all. The severity of symptoms depends on the person, their response to the foods they eat, and other factors.  

Lactose intolerance may be confused for a milk allergy, but being allergic to milk is a very different thing. A milk allergy is caused by an immune reaction to milk proteins and can be life-threatening. Infants and children with a milk allergy may have symptoms such as hives, wheezing, vomiting, and swelling of the face or throat. Anaphylaxis is a severe, life-threatening reaction to milk products that warrants immediate medical attention. 

How is lactose intolerance diagnosed?

How do you know if you have lactose intolerance? Some people may suspect they have lactose intolerance if they experience digestive symptoms after consuming a dairy product. However, many of the symptoms of lactose intolerance are similar to those of irritable bowel syndrome, celiac disease, and gastrointestinal infections. If you suspect you are lactose intolerant, it is important to speak with your primary care provider to get a formal diagnosis and make sure there are no other medical or nutritional concerns. 

A healthcare provider will diagnose lactose intolerance by evaluating your overall medical history. They may ask you about your personal or family medical history and perform a physical exam to pinpoint the cause of your symptoms. They may also perform medical tests to help accurately diagnose the condition. Diagnostic medical tests for lactose intolerance include:

Hydrogen breath test

A hydrogen breath test, which is administered by a gastroenterology specialist, measures how much hydrogen is in the breath after consuming dairy products. It tests for hydrogen because the body turns undigested lactose into hydrogen gas.  

Blood glucose test

Blood glucose tests are another type of laboratory test that can help diagnose lactose intolerance. A blood glucose test looks for elevated blood glucose levels after a person consumes a standard amount of lactose. If blood glucose levels don’t go up, the body isn’t breaking lactose down into glucose. 

Stool acidity test

The bacteria in the large intestine ferment lactose, releasing lactic acid and causing high acidity in the stool. A healthcare provider may test the stool for a low pH level, which would indicate high acidity. Because a stool acidity test is not specific for lactose malabsorption, a healthcare provider may also recommend removing dairy products from the diet. 

Removal of dairy items from the diet

A healthcare provider may recommend removing dairy and milk items from the diet and then slowly reintroducing those items back into the diet. If symptoms are absent while abstaining from dairy products and reappear after consuming dairy products, lactose intolerance may be a concern.

Lactose intolerance treatments

Managing this intolerance is usually a matter of making diet changes, but lactase enzyme supplements may be helpful for some people.

Diet changes

Many doctors agree that the best way to treat an intolerance is to avoid consuming lactose to begin with. Lactose is in dairy products and non-dairy products, so reading food and medication labels is important.

Dairy foods and drinks that are high in lactose include:

• Cow’s milk
• Goat’s milk
• Breast milk and milk-based formula
• Ice cream
• Half and half 
• Some yogurt (Greek yogurt has less lactose than other yogurts)
• Dry milk powder, milk solids, and milk by-products
• Cheese, especially soft cheeses (Parmesan, Swiss, and cheddar have less lactose)
• Cream cheese
• Cottage cheese
• Heavy cream
• Buttermilk 
• Condensed milk
• Sherbert
• Coffee creamers 
• Butter
• Ghee
• Whey 

Non-dairy sources of lactose:

• Medications
• Instant coffee
• Margarine
• Salad dressings
• Processed grains

Checking food labels is the best way to see whether or not a packaged food item or medication has lactose in it—the label will read “dairy-free” or “lactose-free.” Even small amounts can be difficult to digest, and some foods might cause more symptoms than others.  

“For some, eating yogurt is low enough in lactose not to cause problems,” Barry Sears, Ph.D., author of The Zone Diet series says. “Hard cheese is much lower in lactose, and lactose-free dairy products have no lactose at all.” The best way to determine which foods cause the most trouble for you is to eliminate all sources of lactose for a week or two, and then add them back in one at a time.  

For infants and children, both breast milk and milk-based formulas contain lactose. If parents believe an infant might have a lactose intolerance, they should consult their pediatrician and consider eliminating dairy from their diet (if breastfeeding) or switching to non-dairy infant formula. Parents should discuss their concerns with their pediatrician before eliminating foods from their children’s diet to ensure adequate nutrition and growth.

Lactase supplements

Some medicines help the digestive system process lactose. Over-the-counter drops and tablets that contain the lactase enzyme may help with digestion. Adding drops of lactase to milk before drinking it, or taking a lactase tablet before eating dairy products can make a big difference.  

Lactase is the active ingredient in products like Lactaid and Lac-Dose. Generic lactase enzyme tablets and capsules are also available. People with lactose intolerance should take a lactase supplement before eating anything with lactose in it. Although this type of supplement works well for some people, it isn’t a cure.   

RELATED: What is Lactase? | What is Lactaid? 

Lactose-free alternatives

Many people with lactose intolerance enjoy eating milk or dairy products but want to avoid triggering their symptoms. Eating or drinking lactose-free alternatives may help avoid symptoms while still taking advantage of the benefits of dairy products. Many lactose-free alternatives are fortified with calcium and vitamin D that a person would otherwise get from regular milk products. 

Cow milk alternatives: Several alternatives to cow milk are available. The most popular options include nut milks, such as almond and cashew milk. Nut milks are often a low-calorie substitute for cow milk but lack some nutrients that cow milk provides. You’ll need to make sure you’re getting enough nutrients like fiber and protein from other sources. Soy, rice, and coconut milk are other tasty lactose-free options that often come in sugar and non-sugar free formulations.  

Butter alternatives: Lactose-free butter alternatives include olive oil and coconut oil. Olive contains monounsaturated fats, which may provide some health benefits that regular butter doesn’t provide. However, olive oil is high in calories so some people may need to watch their intake. Coconut oil is another alternative to butter that has a unique taste. You can modify your use of butter alternatives depending on what the recipe calls for. 

Cheese alternatives: Many people who avoid dairy products are able to easily find foods that resemble the taste and texture of cheese. Tofu is a great soft cheese alternative that is packed with protein. It may be a good alternative for cheeses like ricotta and cottage cheese. Nutritional yeast has a nutty, creamy texture and flavor when used to make a lactose-free cheese alternative. It’s also a good source of vitamin B12. 

Ice cream alternatives: People who want to avoid dairy and milk-based ice cream can turn to fruit-based frozen treats. Sorbets are usually made with ice and fruit and can be sweetened to your liking. Frozen bananas can also be used to make a dairy-free ice cream. Just add frozen bananas and any other desired ingredients into a blender and you can easily make a tasty ice cream alternative at home.  

Can you still consume dairy and milk products with lactose intolerance?

Some people with lactose intolerance are still able to consume milk and dairy products. The severity of symptoms depends on the person and how they respond to milk and dairy products. It’s best to keep a food diary to see which foods might be causing the worst symptoms for you. 

If you’re concerned that taking dairy products out of your diet will mean you’re not getting enough vitamin D or calcium, you can try adding other foods into your diet. Milk isn’t necessary outside of infancy, so it’s very possible to supplement the nutrients from milk with other products. Fatty fish, eggs, mushrooms, green leafy vegetables, and nuts are all great sources of calcium and vitamin D. 

When to call a healthcare provider?

If you find that you’re becoming more sensitive to dairy products and experiencing severe digestive systems, such as diarrhea or an upset stomach, you should check in with your healthcare provider. If you’ve already started to cut out dairy products and still find that you’re experiencing digestive issues, you should also call your healthcare provider. Your healthcare provider can identify exactly what is causing your symptoms. They can also rule out other possible problems, such as:

• Milk allergy
• Irritable bowel syndrome
• Inflammatory bowel disease
• Crohn’s disease
• Celiac disease 
• Gastrinoma
• Gastroenteritis
• Giardiasis
• Intestinal infection 

They can also guide you on how to best treat your symptoms. Identifying lactose intolerance early can help prevent potential complications, such as:

• Malnutrition 
• Growth issues
• Bone problems
• Weight loss

The best way to learn more about lactose intolerance and how to treat it is to talk with your healthcare provider and dietitian.

Living with lactose intolerance

Lactose intolerance may never completely go away for someone genetically predisposed to it. It’s possible to manage symptoms, and many people find that their symptoms go away within a couple of days after eliminating dairy products from their diet. However, lactose intolerance is a tolerable condition that doesn’t require extreme measures to treat. The best way to deal with it is to avoid the foods that trigger symptoms the most.

If you or someone you know has lactose intolerance, several options are available to help make living with lactose intolerance easier. Over-the-counter lactase enzyme supplements may help with digesting lactose products. You can also try lactose-free alternatives that have the same taste and texture as their dairy counterparts. Just make sure to talk with your healthcare provider about getting the right nutrients from other foods.