An Overview of Lactose Intolerance

You don't need to avoid dairy completely if you're lactose-intolerant

Bowl of yogurt with granola and raspberries

Verywell / Zorica Lakonic

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Lactose intolerance occurs when your body has a problem digesting lactose, a sugar found in milk. When you're lactose-intolerant, you may experience abdominal discomfort and digestive issues after consuming dairy products such as milk, ice cream, yogurt, and cheese.

This is not an uncommon condition and it's fairly easy to treat. If you have lactose intolerance, you can avoid the effects by limiting the lactose-containing foods you eat. Or you can use over-the-counter enzyme replacements to help you digest lactose better, but you have to make sure to get the timing right.


Lactose intolerance can affect children and adults, and it can begin by the age of two. If you have lactose intolerance as a child, it can be a problem throughout your life or you may outgrow it. It is more common to develop lactose intolerance as you get older, however.

Common effects of lactose intolerance include:

  • Abdominal cramping
  • Gas
  • Bloating
  • Nausea
  • Diarrhea
  • Abdominal pain

Most of the time, these symptoms occur between half an hour to a couple hours after eating dairy products.

Consuming larger amounts of lactose-containing food and drinks typically induces more severe symptoms.


If you have severe lactose intolerance, you can experience complications. Recurrent vomiting or diarrhea can cause dehydration, weight loss, or electrolyte imbalances.

If you have a gastrointestinal (GI) infection, you can experience more noticeable effects of your lactose intolerance until your infection resolves. And if you have a GI condition such as inflammatory bowel disease or irritable bowel syndrome, it can exacerbate your lactose intolerance.

Nutritional Effects

Some people who have lactose intolerance avoid all dairy products and may become deficient in important nutrients such as calcium, vitamin D, and protein. These deficiencies can cause a number of health effects, effects such as bone fragility.


Consuming foods and beverages that contain lactose results in the effects of the allergy. There are many foods and beverages that can induce the effects of lactose intolerance.

Common triggers of lactose intolerance include:

  • Milk
  • Ice cream
  • Cheese
  • Yogurt
  • Smoothies
  • White, milk-based sauce
  • Food cooked with cheese, such as pizza or macaroni and cheese
  • Cream dessert filling
  • Custard and pudding
  • Whipping creams
  • Milk-based creamer, half and half

Some people experience lactose intolerance from consuming certain foods, but not others.


Lactose is a type of sugar found in milk. Your body needs lactase enzyme (which is produced in the small intestine) to break down lactose into glucose and galactose—sugars that your body can absorb and use. Lactose intolerance occurs when your body doesn't have enough lactase enzyme.

If you can't properly break down lactose, it remains in your digestive system until it is eventually excreted in the feces instead of being absorbed. Excess lactose in your digestive system causes fluid to flow into your colon—which results in the symptoms of lactose intolerance, such as diarrhea and stomach cramps.

Lactose intolerance may occur for several reasons:

  • Lactose non-persistence: The most common cause of lactose intolerance is a decrease in lactase enzyme as you get older.
  • Digestive disorders : Conditions such as Crohn's disease or celiac disease can damage the intestinal cells that produce lactase.
  • Hereditary: The least common cause of lactose intolerance is hereditary and may begin from birth. Infants with this condition may be unable to digest breast milk and require a lactose-free formula.

Even when you have low amounts of lactose, a naturally occurring bacteria called lactic acid bacteria can break down lactase. Some people have a reduced effect of this bacteria.

Keep in mind that lactose intolerance is not an allergy to milk. An allergy is very different, and the effects of an allergy are mediated by an inflammatory reaction.


If you experience symptoms of lactose intolerance, it is best to speak with your healthcare provider to get a formal diagnosis and advice that is tailored specifically to your health and medical needs.

Many people self-diagnose their own or their children's lactose intolerance. Keep in mind that you could be experiencing another medical problem that produces symptoms similar to those of lactose intolerance, such as an infection, inflammatory bowel disease, malabsorption, or a food allergy.

Elimination Diet

An elimination diet may be helpful in diagnosing lactose intolerance. Using this type of diet, you would eliminate all dairy products to see if the symptoms resolve. It is important to only eliminate one category of food (such as dairy) when using an elimination diet so the outcome will not be confusing.

Diagnostic Tests

Lactose intolerance can be diagnosed by a variety of tests. These include a lactose tolerance test, a breath test, or a stool sample test.

  • Lactose tolerance test: A blood test, called a lactose tolerance test, can measure your fasting glucose level. You would then be given a drink containing lactose. If you can't properly break down and absorb lactose, your blood glucose level will not rise as much as expected after consuming the drink.
  • Hydrogen breath test: This test measures the hydrogen in your breath after you drink a lactose-containing beverage. High amounts of hydrogen on your breath suggest that you may not be able to break down the lactose.
  • Stool sample: The stool test measures undigested lactose in the stool, and it is often used for infants and young children.


Treatment for lactose intolerance consists of either avoiding lactose-containing food or supplementing your body's supply of lactase enzyme.

You may notice that you are able to tolerate cheese but not ice cream, or yogurt but not milk. It is perfectly fine to consume the foods and drinks that do not cause any problems for you—while avoiding the products that cause you to experience physical distress.

Dietary Changes

Most dairy products contain lactose, but not all dairy products have a high concentration of lactose. For example, hard cheeses are made only from milk protein and include little or no lactose sugar.

Fermented dairy products are lower in lactose, and you may tolerate them better. That's because they're produced by allowing bacteria to convert some or all of the lactose into lactic acid. Fermented dairy products include yogurt, kefir, sour cream, buttermilk, and crème fraîche.

Lactose-free milk and lactose-free ice cream are available in most grocery stores. Most people who have lactose intolerance do not experience symptoms when consuming these lactose-free dairy options.

Lactase Supplements

There are ways to consume lactose-containing food and beverages even if you are lactose intolerant.

Over-the-counter lactase enzyme supplements can be taken before eating dairy products. Be sure to follow the package directions when taking these so that you will have the beneficial effects at the right time.

Probiotics—helpful bacteria that naturally live in the digestive tract—may help alleviate symptoms in some people with lactose intolerance. If your healthcare provider suggests probiotics for you, you can either take them in the form of yogurt or as capsules, which are typically found in refrigerated sections of health food stores.

A Word From Verywell

Lactose intolerance affects 70% of the worldwide population. In general, this condition causes physical discomfort, but it is rarely dangerous for your health. If you do need to avoid dairy products entirely, be sure to replace the nutrients found in milk by eating other foods that contain protein, calcium, and vitamin D.

Frequently Asked Questions

  • How common is lactose intolerance?

    Worldwide, around 65% of adults are lactose intolerant. It's uncommon for children under 5 to have the condition.

  • What happens in your body when you're lactose intolerant?

    Your small intestine is unable to digest a sugar called lactose due to a lack of an enzyme called lactase. That lactose moves along your digestive tract to the colon, where bacteria feed on it. This produces gas that causes flatulence and bloating, diarrhea, and other symptoms.

  • Is it possible to suddenly become lactose intolerant?

    Yes. Some people, especially those of African, Asian, or Hispanic descent, produce increasingly less lactase with age and so can develop lactose intolerance later in life. Similarly, anyone with a condition that damages the lining of the small intestine, such as celiac disease, tropical sprue, or an acute infection, can become lactose intolerant.

  • What are the best alternative sources of calcium for people with lactose intolerance?

    Among the richest non-dairy sources of calcium are:

    • Calcium-fortified foods and beverages, such as orange juice, soy milk, cereals, and bread
    • Canned fish with bones, such as sardines and salmon
    • Leafy green vegetables, including broccoli, collards, mustard greens, kale, and bok choy
    • Almonds and Brazil nuts
    • Sunflower seeds
    • Tahini
    • Blackstrap molasses
    • Dried figs

  • Should I take calcium supplements if I'm lactose intolerant?

    If you're unable to eat any amount of dairy foods and can't meet the recommended daily allowance for calcium with alternative sources of calcium, a supplement likely is advisable. Talk to your healthcare provider or a dietitian about the best type of calcium supplement for you (calcium citrate or calcium carbonate) and how much you should take based on your regular diet. A typical recommendation is 1,200 to 1,500 milligrams per day.

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Article Sources
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