Highlights:

• Evidence shows many people can still enjoy dairy foods such as milk, cheese and yogurt, even if they have lactose intolerance.
• Limiting the intake of dairy foods due to lactose intolerance means needlessly missing out on the health benefits of dairy.
• People diagnosed with lactose intolerance can tolerate some lactose. Rather than cutting all dairy, patients can adjust lactose intake according to tolerance.

Some people have trouble digesting lactose, but that doesn’t mean giving up dairy! Read on to learn more about lactose intolerance, how it’s formally diagnosed, and how you can provide the best nutrition advice to patients.

What is lactose?

Lactose is a type of naturally occurring sugar found in milk. It is produced by mammary glands of animals, so their resulting milk contains lactose. Cow’s milk naturally contains about 5 percent lactose¹.

Fermented cow’s milk in yogurt has less lactose than in fluid milk because of the conversion of lactose by lactic acid bacteria. Hard cheeses contain very low levels or no lactose, while soft cheese may have more lactose depending on the production process².

What is lactose intolerance?

Lactose intolerance is the inability to digest lactose, a natural occurring sugar found in milk and other dairy products. Humans require lactase enzyme to break down lactose³.  When this enzyme is in short supply, lactose isn’t broken down and gets fermented by the gut microbiota, which leads to symptoms such as:

• Diarrhea
• Abdominal pain
• Cramps
• Bloating
• Flatulence⁴

These symptoms usually begin about 30 minutes to two hours after consuming milk if you are lactose intolerant⁵.

Lactose intolerance vs. milk allergy

Lactose intolerance is often confused with a milk allergy, but the two are different. Lactose intolerance affects the digestive system and is a gastrointestinal reaction to lactose; it does not elicit an immune response. A milk allergy is an immune-mediated reaction to the protein in milk.

Symptoms of milk allergy may include gas, cramps, and diarrhea (which is why it’s often confused with lactose intolerance) but may also include traditional allergy symptoms such as hives or wheezing⁶.

Types of lactose intolerance

There are three distinct types of lactose intolerance⁷:

1. Primary lactose intolerance: The most common form; the result of low levels of lactase enzyme. It’s usually diagnosed in teen or early adult years.
2. Secondary lactase deficiency: A transient condition that comes after suffering intestinal damage from an infection, antibiotic use, celiac disease, Crohn’s disease, etc. It can happen at any age.
3. Congenital lactase deficiency: An extremely rare condition that starts at birth. Only 40 cases have been reported to-date globally.

Who gets lactose intolerance?

Lactase activity is high at birth since breast milk contains lactose. Tolerance progressively declines after weaning, and some can digest more lactose than others. The ability to digest lactose is common in populations that raise cattle and consume more dairy foods, as well as their descendants^8.

Lactose intolerance likely started due to a genetic mutation in the LTC gene, which is responsible for making lactase enzymes⁹.  This condition is most common in people from East Asian, African and South American descent. It’s least common in people from Northern European descent¹⁰.

How is lactose intolerance diagnosed?

Patients who have gas or cramps after they drink milk may think they have lactose intolerance and may erroneously self-diagnose. This is potentially harmful since they may cut out milk unnecessarily before a definitive diagnosis.

The most accurate diagnosis comes from a non-invasive hydrogen breath test, though lactose intolerance can also be diagnosed by a blood test¹¹.  It’s important to obtain a true diagnosis, because symptoms such as gas, cramps and bloating may be part of many different digestive disorders. In fact, lactose intolerance is just one potential cause of digestive symptoms.

If it’s not lactose intolerance, what else could it be?

The symptoms of lactose intolerance can overlap with different digestive disorders, so it’s important to ensure patients are properly tested and diagnosed. Other conditions that may share symptoms with lactose intolerance include ^{12, 13}:

• Milk allergy
• Other food allergies
• Celiac disease
• Irritable bowel syndrome and associated FODMAP triggers
• Colitis
• Crohn’s disease
• Excessive sugar intake

Managing lactose intolerance

Eliminating milk and other dairy products is not a necessary treatment for someone who is diagnosed with lactose intolerance¹⁴.  This is a common misconception.

Several international health organizations and authorities such as the National Institute of Health, National Medical Association and the American Academy of Pediatrics Committee on Nutrition, recommend that individuals with lactose intolerance do not need eliminate milk and dairy products from their diet. ^{15, 16, 17}

Lactose intolerance varies from mild to severe¹⁸.  Some people with lactose intolerance can consume 12-24 grams of lactose daily if the amount is spread out over the day and consumed as part of mixed meals¹⁹.  Most people can digest a cup of milk (about 12 g lactose) with no problem²⁰.  Here’s a chart that shows the amount of lactose in a variety of dairy products:

Chart information from the Canadian Society of Intestinal Research

Why is cheese often low in lactose? Hard matured cheeses tend to have less lactose than soft cheese. This is because lactose is lost when whey is removed, and bacterial cultures are added during the cheese-making fermentation process. As the cheese ripens and matures, the lactose gets converted into lactic acid, which does not cause intolerance²¹.

Patients with lactose intolerance can manage their symptoms without cutting out milk entirely. They can test which of these methods works best for them – perhaps it’s a combination of these tips²²:

• Use lactase enzyme supplements before ingesting foods that contain lactose. These supplements help break down lactose, making lactose-containing foods easier to digest²³.
• Try dairy products that are low in lactose, such as hard cheese (see chart above).
• Use lactose-free dairy products. Choose milk, cheese and yogurts that are specifically labelled “lactose free.”
• Enjoy fermented dairy products such as yogurt, kefir and hard cheese. The fermentation process includes the use of bacteria that help break down lactose.
• Eat lactose-containing foods at meals alongside other foods. Digesting other foods at the same time slows gastric emptying, and lactose makes up a smaller percent of the total food being digested. Less lactase enzyme is needed to break down the lactose.

What is lactose free milk? Lactose-free milk is made by introducing lactase enzyme into milk. The lactase breaks down the natural occurring lactose in milk, allowing people with lactose intolerance to continue to enjoy milk.

Milk and health benefits

For patients with lactose intolerance, avoiding dairy isn’t the answer. Milk is a nourishing whole food and is source of 15 essential nutrients including protein, calcium, vitamin D and vitamin B12.

Many studies support the importance of milk, cheese and yogurt as part of a healthy eating pattern. In addition to dairy foods contributing to bone and dental health, studies have linked these foods to other health benefits including reduced risk of stroke, metabolic syndrome, hypertension, colon cancer, and type 2 diabetes. ^{24, 25, 26, 27, 28} 

Plus, lactose may act as a prebiotic in the digestive system and help enhance the microbiome. People with lactose intolerance who consume dairy can develop colonic adaptation by the microbiome due to the consistent presence of lactose. This process may mimic a prebiotic effect and help people with lactose intolerance develop an ability to tolerate lactose and consume more dairy foods.