Ignoring lactose intolerance can exacerbate the symptoms or cause additional health problems. It may also affect someone’s quality of life and mood.

Lactose intolerance, which results from the inability to break down lactose properly, may develop in childhood or early adulthood. It causes digestive symptoms such as diarrhea and gas. People may manage these symptoms with dietary modifications and supplements, and a doctor can give advice about any underlying health conditions.

This article explores lactose intolerance in more detail, including its causes, symptoms, and treatment. It also discusses what may happen if someone keeps consuming dairy.

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Lactose intolerance is a condition that causes symptoms when someone eats or drinks products that contain lactose. Lactose is a sugar that occurs naturally in dairy foods such as milk, cheese, and yogurt.

An enzyme called lactase digests the sugar in dairy products, which helps the body absorb and utilize it. However, people with lactose intolerance produce either insufficient lactase or none at all.

A lack of the enzyme leads to lactose malabsorption, which results in unpleasant digestive symptoms. Lactose intolerance is not the same as a milk or dairy allergy. Food allergies involve an inappropriate immune response to certain foods.


Symptoms of lactose intolerance can appear between 30 minutes and 2 hours after someone ingests dairy products. These symptoms may include:

Less commonly, people may experience muscle or joint pain, a headache, or loss of concentration.

Causes of lactose intolerance

Lactose intolerance occurs when someone has a deficiency of the enzyme lactase.

Scientists believe that there are four leading causes of lactase deficiency.

Primary lactase deficiency

The most common form of lactose intolerance is lactase nonpersistence. This is a gradual decline in lactase activity, beginning in infancy. The symptoms may start in childhood or early adulthood.

Secondary lactase deficiency

Injury to the cells lining the intestines can cause a deficiency in lactase. This may be due to:

Congenital lactase deficiency

In rare cases, someone may inherit a congenital lactase deficiency. In these cases, symptoms may occur as soon as an infant ingests milk.

Developmental lactase deficiency

Infants born prematurely may have underdeveloped intestines that compromise their ability to digest and absorb lactose. As the intestines mature with age, the symptoms may improve in time.

If someone with a lactose intolerance continues to consume too much lactose, they may experience worsened symptoms, lower mood, and a reduced quality of life.

Chronic diarrhea may lead to complications such as malnutrition, unexplained weight loss, and anemia. It may also cause dehydration or acute kidney injury if the intestines cannot absorb enough fluids.

Additionally, someone with lactose intolerance who only gets calcium from dairy products may risk their bone health. Calcium is an essential nutrient for healthy bones and preventing osteoporosis. A person may wish to consider including alternative sources of calcium, such as plant-based foods and fortified products, in their diet.

Doctors treat and manage lactose intolerance in various ways.

Dietary modification

A doctor may advise someone to avoid or limit dairy products, including:

  • milk
  • cream
  • sour cream
  • ice cream
  • butter
  • whey
  • buttermilk
  • soft and processed cheese

People may be able to eat smaller amounts of Greek yogurt or hard cheeses, as they contain less lactose. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) suggests that some people may be able to tolerate 12 grams of lactose.

Additionally, people should be aware that manufacturers or restaurants may add dairy to foods such as:

Someone with lactose intolerance can consume the beneficial nutrients in milk by choosing lactose-free or lactose-reduced types. Additionally, they may wish to purchase plant-based milk and dairy products as an alternative.

Lactase supplements

Lactase supplements contain the enzyme lactase. People may take these supplements in the form of tablets before eating food containing dairy or they may add supplement drops to milk beverages.


Although the current body of research is inconclusive, probiotics have shown positive results in treating lactose intolerance. Particular strains, such as the DDS-1 strain of Lactobacillus acidophilus, may help improve the symptoms.

Treatment of an underlying condition

If lactose intolerance occurs due to an underlying digestive condition, a doctor may help a person improve their symptoms by providing treatment for the underlying condition.

Avoiding all dairy products is the only way for people with lactose intolerance to prevent symptoms.

People can choose plant-based alternatives to dairy products, but they should be mindful of consuming enough calcium to prevent osteoporosis.

Other people with lactose intolerance may be able to tolerate smaller amounts of dairy products with no symptoms.

Below are some common questions about lactose intolerance.

How can someone prevent lactose intolerance?

Avoiding all dairy products is the only way to prevent lactose intolerance. However, someone may be able to manage their symptoms by making dietary modifications and taking lactase supplements.

Are there stages of lactose intolerance?

With the most common forms of lactose intolerance, a person’s symptoms might start early in life or worsen as they age. Additionally, if someone eats too much dairy or other products containing lactose, they may find that their symptoms get worse.

What are the symptoms of lactose intolerance?

The symptoms can include:

  • gas and bloating
  • diarrhea
  • nausea or vomiting
  • abdominal pain

People who ignore their lactose intolerance and continue to eat too many dairy products risk exacerbating their symptoms and developing further health complications.

Lactose intolerance symptoms may affect a person’s quality of life and mood. For example, chronic diarrhea may lead to malnutrition, dehydration, or anemia.

A doctor may advise people with lactose intolerance to manage their condition with dietary modifications, lactase supplements, and dairy alternatives. However, they should be mindful of eating enough nutrients to support healthy bones and prevent osteoporosis.