An ice cream sundae in the summer heat, a holiday snack of milk and cookies, or a bowl of breakfast cereal might all sound like delicious treats. But these milk-based snacks can ruin the day for those with lactose intolerance. For some people with this condition, it may even be possible to improve their tolerance of lactose. Learn more about how to manage life with lactose intolerance.

What Is Lactose Intolerance?

Lactose is a type of sugar in milk and dairy products that contain milk. In infancy, the body is highly adept at digesting milk with the assistance of an enzyme called lactase. As children turn into adults and their diet shifts from milk to solid food, the ability to digest lactase declines. 

The National Institutes of Health (NIH) estimates that 65% of adults worldwide have a decreased ability to digest lactose, meaning they are lactose intolerant. Some never notice symptoms. Others find that they occasionally feel sick after drinking milk. And some become extremely ill after consuming dairy products.

Lactose intolerance varies by race and ethnicity. Most estimates suggest the following prevalence:

  • Among people of European ancestry, 7-20% of adults are lactose intolerant.
  • Among people of African descent, 70-75% of adults are lactose intolerant.
  • In Asian populations, more than 90% of adults are lactose intolerant.
  • Among Australian Aborigines, lactose intolerance rates are about 70%.

Types of Lactose Intolerance

Lactose intolerance exists on a continuum. Most people with this condition still have some lactase activity, which means they can consume some milk products without getting sick. They might not realize they are lactose intolerant because the symptoms are minor enough never to be connected to milk consumption.

About 25% of Americans have lactose intolerance symptoms severe enough to interfere with daily life. Some experience mild but annoying symptoms. Others get so sick when they drink milk that they have to avoid it completely.

There are four types of lactose intolerance:

  • Primary lactose intolerance: The most common form of lactose intolerance, primary lactose intolerance is an intolerance that develops with time. Many researchers argue that it’s an evolved tendency. Babies need to be able to digest milk, but as they shift to solid food, they no longer need milk. So the body doesn’t waste resources maintaining lactase.
  • Secondary lactose intolerance: Secondary lactose intolerance is lactose intolerance that develops because of something else, such as an illness or surgery. For instance, damage to the small intestine can interfere with its ability to make lactase, which can cause lactose intolerance. An adult who previously digested milk without a problem but who suddenly gets sick from milk likely has secondary lactose intolerance.
  • Developmental lactose intolerance: Developmental lactose intolerance is lactose intolerance in babies. It’s more common in babies born prematurely, who haven’t yet developed the ability to digest lactose. It typically goes away on its own.
  • Congenital lactose intolerance: Congenital lactose intolerance is genetic lactose intolerance that is present from birth. It’s extremely rare and requires both parents to pass on a gene that removes the ability of the small intestine to secrete lactase.

Symptoms and Causes

The small intestine secretes different enzymes that help the body break down various foods. When it doesn’t secrete lactase, a person becomes lactose intolerant. In some people, the small intestine still secretes lactase, but not enough. They may experience periodic bouts of gastrointestinal problems or only experience symptoms when they eat or drink a lot of dairy products.

Lactose intolerance is not the same thing as a milk allergy. If you are allergic to milk, you will get severely ill if you consume any milk products. If you are lactose intolerant, you can have lactose-free dairy products. Some other distinctions between the two conditions include:

  • Symptoms of a milk allergy typically begin in childhood, while lactose intolerance is more common in adults.
  • Symptoms of a milk allergy tend to appear within a few minutes of drinking milk. Most people with lactose intolerance develop symptoms within 30 minutes to 2 hours of consuming dairy products.
  • A milk allergy produces more severe symptoms than lactose intolerance. In some people, a milk allergy triggers life-threatening anaphylaxis that warrants immediate medical attention.

Symptoms of lactose intolerance can change over time. They can be severe or mild, and they can depend on the amount of milk a person consumes. The most common symptoms include:

  • Bloating, stomach pain, and gas
  • Nausea and diarrhea
  • Constipation
  • Feeling generally unwell
  • Low energy
  • Vomiting

Prevention and Risks

There’s no evidence that lactose intolerance is preventable. Some people may be more at risk. Risk factors include:

  • Being born prematurely
  • Being of African, Asian, Latinx, or indigenous descent
  • Having a disease that affects the small intestine
  • A history of chemotherapy or radiation for cancer

Diagnosis and Tests

Lactose-free products are safe, and few people need to consume milk to stay healthy. Many doctors diagnose lactose intolerance based solely on symptoms. People who need a specific diagnosis have a few testing options. Those include:

  • Lactose tolerance tests: For this test, you’ll drink a liquid that’s high in lactose. Two hours later, you’ll undergo blood work that measures how much glucose is in your blood. If your glucose doesn’t go up, it means your body can’t digest or absorb lactose.
  • Hydrogen breath test: This test also involves drinking a high-lactose drink. Next, a doctor uses a machine to measure how much hydrogen is in your breath. When the body can’t digest lactose, it ferments in the intestines. This causes you to release more hydrogen in your breath.
  • Stool acidity test: This test uses a stool sample to test for lactic acid in a bowel movement. Doctors typically recommend this test for babies and children.

Treatment, Procedures, and Medication

No medication or surgery can cure lactose intolerance. Here are several ways to help manage lactose intolerance:

  • Reduce the amount of lactose-containing products you consume.
  • Use medications and foods that contain lactase, the enzyme that helps the body digest lactose.
  • Find other sources of calcium and vitamin D.

Healthy Lifestyle Tips

Some people who are lactose intolerant worry that reducing or eliminating milk products will put them at risk of vitamin D or calcium deficiency. Calcium and vitamin D are essential nutrients that work together to support healthy bones and prevent osteoporosis. Milk is also an important source of fat and protein for vegetarians.

Avoiding milk doesn’t have to mean dealing with nutritional deficiencies. In fact, some evidence suggests that milk might not be the ideal source of calcium, vitamin D, or protein. According to the Physicians Committee for Responsible Medicine, some data has found that animal proteins leech calcium from the bones. So getting calcium from other sources, particularly calcium-rich vegetables such as dark leafy greens, might be a better option.

A healthy lifestyle can also prevent bone loss. Try the following:

A 2014 study published in Nature found that, for some people, lactose intolerance might improve health. Researchers analyzed data of more than 22,000 people with lactose intolerance. They had a lower risk of breast, lung, and ovarian cancers than those without lactose intolerance. After controlling for diet and lifestyle factors, researchers discovered that this result was because the group consumed fewer dairy products. So limiting dairy consumption may offer some health benefits.

Food and Nutrition-Based Approaches to Prevention and Management

Most people with lactose intolerance can still drink some milk. Try reducing your use of milk products to see if your symptoms improve. People who find that this doesn’t help, or those who want to avoid milk, should try the following:

  • Drink only lactose-free milk.
  • Use milk substitutes, such as almond milk.

People who can’t reduce their dairy consumption or who have severe symptoms can try a lactase supplement. This temporarily boosts lactase in the small intestine, making it possible to drink milk. Follow the supplement’s instructions, and talk to a doctor before trying any supplements or over-the-counter drugs. You may need to limit your use of lactase supplements. Some people also find that lactase supplements cause unpleasant side-effects.

What Type of Doctors to See

A family physician or general practitioner can usually help with diagnosing lactose intolerance. You may need a referral to an allergist or gastroenterologist. Lactose intolerance in a child warrants a consult with a pediatric allergist or gastroenterologist.

Babies who are lactose intolerance may need the support of a nutrition team, including a lactation consultant, pediatrician, nutritionist, or gastroenterologist. If a newborn shows signs of lactose intolerance, see a doctor immediately. When a baby can’t absorb formula or breast milk, they can suffer serious nutritional deficits.

Conclusion

For most people, lactose intolerance is little more than an annoyance. It doesn’t mean there’s an underlying serious health problem and doesn't require treatment. Talking to a doctor about symptoms may help ease your mind and support you to develop a healthy lactose-free lifestyle. You can also just steer clear of lactose and see if symptoms get better.

If you think your child might be lactose intolerant, don’t self-diagnose. See a doctor, and know that lactose intolerance in a newborn may be a medical emergency.