Definition & Facts for Lactose Intolerance

In this section:

• What is lactose intolerance?
• How common is lactose malabsorption?
• Who is more likely to have lactose intolerance?
• What are the complications of lactose intolerance?

What is lactose intolerance?

Lactose intolerance is a condition in which you have digestive symptoms—such as bloating, diarrhea, and gas—after you consume foods or drinks that contain lactose. Lactose is a sugar that is naturally found in milk and milk products, like cheese or ice cream.

In lactose intolerance, digestive symptoms are caused by lactose malabsorption. Lactose malabsorption is a condition in which your small intestine cannot digest, or break down, all the lactose you eat or drink.

Not everyone with lactose malabsorption has digestive symptoms after they consume lactose. Only people who have symptoms are lactose intolerant.

Most people with lactose intolerance can consume some amount of lactose without having symptoms. Different people can tolerate different amounts of lactose before having symptoms.

Lactose intolerance is different from a milk allergy. A milk allergy is an immune system disorder.

How common is lactose malabsorption?

While most infants can digest lactose, many people begin to develop lactose malabsorption—a reduced ability to digest lactose—after infancy. Experts estimate that about 68 percent of the world’s population has lactose malabsorption.1

Lactose malabsorption is more common in some parts of the world than in others. In Africa and Asia, most people have lactose malabsorption. In some regions, such as northern Europe, many people carry a gene that allows them to digest lactose after infancy, and lactose malabsorption is less common.1,2 In the United States, about 36 percent of people have lactose malabsorption.1

While lactose malabsorption causes lactose intolerance, not all people with lactose malabsorption have lactose intolerance.

Who is more likely to have lactose intolerance?

You are more likely to have lactose intolerance if you are from, or your family is from, a part of the world where lactose malabsorption is more common. In the United States, the following ethnic and racial groups are more likely to have lactose malabsorption:

• African Americans
• American Indians
• Asian Americans
• Hispanics/Latinos

Because these ethnic and racial groups are more likely to have lactose malabsorption, they are also more likely to have the symptoms of lactose intolerance.

Lactose intolerance is least common among people who are from, or whose families are from, Europe.

What are the complications of lactose intolerance?

Lactose intolerance may affect your health if it keeps you from getting enough nutrients, such as calcium and vitamin D. Milk and milk products, which contain lactose, are some of the main sources of calcium, vitamin D, and other nutrients.

You need calcium throughout your life to grow and have healthy bones. If you don’t get enough calcium, your bones may become weak and more likely to break. This condition is called osteoporosis. If you have lactose intolerance, you can change your diet to make sure you get enough calcium while also managing your symptoms.

References

[1] Storhaug CL, Fosse SK, Fadnes LT. Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis. The Lancet. Gastroenterology & Hepatology. 2017;2(10):738–746.

[2] Misselwitz B, Fox M. What is normal and abnormal in lactose digestion? The Lancet. Gastroenterology & Hepatology. 2017;2(10):696–697.

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