Lactose Intolerance

What Is Lactose Intolerance

What is lactose intolerance?

Lactose intolerance, also known as lactose malabsorption, is a disorder that makes people unable to completely digest lactose—the sugar that is naturally present in all mammalian milk. Because of this, eating or drinking dairy products causes those who have lactose intolerance to have gas, bloating, nausea, and diarrhea.

Up to 65% of all humans have a reduced ability to digest lactose after infancy. It’s estimated that 30 to 50 million Americans have lactose intolerance—but it doesn’t affect all ethnic groups equally. The incidence of lactose intolerance is lowest in populations that have a long history of consuming milk products as a main food source. People of Northern European ancestry are least likely to suffer from it—with only 5% of the population being lactose intolerant—while up to 75% of Native Americans and 90% of East Asian have it. Lactose intolerance is also very common among those of Arab, Jewish, Greek, Italian, and West African descent.

Fermented dairy products are easier to digest, and many cultures that have high rates of lactose intolerance have long histories of consuming only fermented dairy products like yogurt—which are easier for the body to digest from a lactose perspective. As well, goat and sheep’s milk dairy products are often better tolerated by those with lactose intolerance than milk and cheese made from cow’s milk. Why? Goat and sheep’s milk both have shorter amino acid protein chains than cow’s milk, which may be easier to digest.

Awareness of the condition is on the rise, partly due to sufferers making adjustments to avoid the uncomfortable effects of this condition. According to TellTheChef, a service that facilitates pre-orders and group bookings for dining establishments, pre-orders of lactose-free restaurant meals rose by more than 7% in 2014.

There are three major types of lactose intolerance:

Primary lactose intolerance is the most common; it happens when people who had adequate amounts of lactase (a lactose-digesting enzyme produced by cells in the small intestine) in childhood begin producing less of it as they grow up. By the time they reach adulthood, they have trouble digesting milk products.

Secondary lactose intolerance happens when your small intestine cuts back on its lactase production due to surgery, an illness, or an injury. Treating the underlying cause may gradually reverse this.

Lastly, there’s a rare form called Congenital or developmental lactose intolerance—it’s when babies are born with no lactase at all, due to a genetic defect or to prematurity.

What Causes Lactose Intolerance

Lactose intolerance is caused by inadequate levels of lactase, an enzyme that’s normally produced by cells inside the small intestine. In most people, it breaks down milk sugar into two other sugars, glucose, and galactose, that our bloodstream can more easily absorb. But when there isn’t enough (or any) lactase present, lactose in your food ends up moving to your colon, where normal bacteria interact with it—causing gas, bloating, and diarrhea.

Risk Factors For Lactose Intolerance

Lactose intolerance is caused by inadequate levels of lactase, an enzyme that’s normally produced by cells inside the small intestine. In most people, it breaks down milk sugar into two other sugars, glucose, and galactose, that our bloodstream can more easily absorb. But when there isn’t enough (or any) lactase present, lactose in your food ends up moving to your colon, where normal bacteria interact with it—causing gas, bloating, and diarrhea.

There are several factors that increase the risk of developing lactose intolerance. These include:

Premature birth. The intestinal cells that produce lactase don’t develop until late in the third trimester, so babies born early may not have them, or enough of them


  • Native Americans have roughly a 75% chance of being lactose intolerance; for Asian Americans, the odds rise to 90%
  • Small studies have shown than nearly 68% of North American and Israeli Jews may have difficulty digesting milk products.
  • A study by Cornell University found that lactose intolerance is more prevalent in people whose ancestors lived in places where harsh climates made it difficult to raise cattle.

Family history of lactose intolerance

Disease of the digestive system such as gastroenteritis, celiac disease, Crohn’s disease

Cystic fibrosis often goes hand in hand with lactose intolerance

Undergoing chemotherapy or radiation as these treatments may have deleterious effects on the rapidly dividing cells in the small intestine, which produce lactose

Aging. Lactose intolerance most commonly develops in adulthood—it is uncommon in babies and children






Diagnosing Lactose Intolerance

If you think you have lactose intolerance, describe your symptoms to your doctor. He or she may use the following methods to diagnose you:

  • A hydrogen breath test. This is the most common test for lactose intolerance, since it’s simple: After drinking a high-lactose beverage, your physician will gauge the levels of hydrogen in your breath at timed intervals. If the amount is elevated (normally, there should be very little present), it’s a sign that lactose isn’t being processed in your small intestine and instead is fermenting in your colon, releasing hydrogen and other gases.
  • A lactose intolerance test. First, you’ll be asked to drink a beverage that contains high levels of lactose. Two hours later, your doctor will take a blood sample to gauge how much glucose (a sugar your body makes upon properly digesting lactose) is in your bloodstream. If your glucose levels are still low, it’s a sign that you aren’t metabolizing lactose normally.
  • A stool test. This method is normally used only in babies or children too young for the previously mentioned procedures. Instead, their stool is tested for its acidity levels, since undigested lactose ferments and creates lactic acid in the body’s waste.

Symptoms of Lactose Intolerance

You may suffer from lactose intolerance if you experience any of the following within 30 minutes to 2 hours after consuming dairy products:

  • A feeling of fullness or swelling in your abdomen (even if you haven’t had much to eat or drink)
  • Pain in your abdomen
  • Gas
  • Nausea
  • Diarrhea

Your symptoms can range anywhere from mild to severe, depending on how much lactose you ingested, as well as the degree of your lactose intolerance.


While lactose intolerance isn’t curable, it fortunately also isn’t considered dangerous, just uncomfortable. And the upside is that there may be health benefits associated with it. According to a Swedish study of nearly 23,000 lactose-intolerant subjects and their families, people who have this condition have lower rates of ovarian, breast, and lung cancers.

Living With Lactose Intolerance

With some lifestyle adjustments, you should be able to live comfortably even if you have lactose intolerance. These steps may all help. With your doctor’s permission, try them out to see which work best for you:

  • Consume only small amounts of dairy products. Test yourself by eating small amounts of dairy products. Yogurt, sour cream, and cheese may be easier for you to tolerate, because they contain less lactose than milk does. There are also studies suggesting that most lactose-intolerant people can drink an 8-ounce glass of milk with no problems.
  • Consume dairy products with other foods—don’t eat in isolation
  • Choose fermented dairy products like yogurt, kefir, cheese, buttermilk, over fresh products. The live bacterial cultures pre-digest some of the lactose, which results in lower levels of this sugar, and fewer uncomfortable symptoms for those that have this condition
  • Try probiotic supplements of bacteria normally found in human intestines. Those containing lactobacillus reuteri may ease some symptoms.
  • Drink milk that’s made for lactose-intolerant consumers. Products like Dairy Ease and Lactaid have had their lactose already broken down.
  • Use enzyme supplements. There are tablets and food additives on the market today that contain the same enzymes that lactose-digesting bacteria have. Some brand names include Lactrase and LactAid. Using these can help you digest milk products more comfortably.
  • Be alert to hidden sources of dairy in the foods you eat. It may surprise you, but salad dressings, breakfast cereals, instant potato, rice, noodle or soup mixes, and other foods may all contain small amounts of lactose. Scan the ingredients list and be on the lookout for giveaway terms, including dry milk powder, curds, yogurt, butter, caseinates, nougat, whey, cheese, milk by-products, dry milk powder, and lactose itself.
  • If even small amounts of dairy bother you—avoid altogether and enjoy healthy alternatives. The best way to avoid digestive upset is to steer clear of dairy products altogether. Try substituting nut milks (almond, cashew, etc.) and nut cheeses for dairy. Delicious!


Your doctor may not screen you for lactose intolerance unless you bring your symptoms to her attention, so be sure to mention these problems. Telltale signs include a feeling of abdominal fullness or bloating soon after eating milk products, along with excessive gas, cramping, nausea, and diarrhea. Your doctor may conduct diagnostic tests to determine whether or not you’re lactose intolerant.


There are no known ways to prevent developing lactose intolerance. But by taking steps such as avoiding or limiting your intake of dairy products, seeking out lactose-free milk or drinking almond, soy, or other plant-based milks and cheeses, and taking supplements that break down lactose in foods, you can minimize your symptoms.

Medication And Treatment

Lactose intolerance is treated with over-the-counter medications that ease symptoms. These consist of pills or drops that contain the same enzymes found in the bacteria that digest lactose. Brand names include Lactrase or Lactaid.

Complementary and Alternative Treatment

Some people turn to probiotics—supplements of bacteria normally found in human intestines—to help ease their lactose intolerance. Probiotics can come in capsule form, or be taken by eating foods that are rich in them, such as yogurts or kefir (drinkable yogurt) that have live active cultures. Generally, probiotics are considered quite safe, so with your doctor’s okay, they’re worth a try.

Care Guide

Lifestyle changes like these can be very effective in eliminating or minimizing the uncomfortable effects of lactose intolerance:

  • Avoiding or limiting dairy products or consuming only those that are lactose free.
  • Using supplements that contain the enzymes produced by lactose-digesting bacteria.
  • Trying probiotic supplements—capsules that contain the same organisms normally found in human intestines.
  • Eating probiotic-rich foods, such as yogurt that’s labeled as having “live active” cultures.

When To Contact A Doctor

If you think you may have lactose intolerance (clues include abdominal fullness or swelling shortly after eating dairy foods, along with gas, bloating, and diarrhea), schedule an appointment with your doctor. She may ask you to lay off dairy products for a week or two, and then report on whether your symptoms subside. To confirm the diagnosis, she can conduct a breath or blood test.



Questions For Your Doctor

Your primary care physician should be able to diagnose your lactose intolerance, and discuss ways to address it with you. If you don’t already have a physician, ask trusted friends and family members for recommendations, or reach out to a local teaching hospital (one that’s affiliated with a medical school) and request a referral.

Questions For A Doctor

Help yourself, and your doctor, by asking these questions at your appointment:

  • Are the symptoms I am describing typical of a person who might have lactose intolerance?
  • What tests can you perform to confirm or rule out lactose intolerance?
  • Are there any lifestyle changes I can make to improve my symptoms?
  • Do you recommend any over-the-counter remedies, supplements, or alternative therapies?
  • Could there be an underlying condition causing my lactose intolerance?


If you suffer from lactose intolerance, or think that you might, the following resources may be helpful to you:

The Eat Confidently With Lactose Intolerance website (Operated by the National Dairy Council) offers tips on how people with lactose intolerance can still enjoy dairy foods. In addition to giving a comprehensive overview on the condition, it features recipes and a community section in which sufferers can share their experiences, insights, and advice.

The National Institute of Diabetes and Digestive and Kidney Diseases. This government-run organization features an extensive “What I Need to Know About Lactose Intolerance” page on its website. Begin there for links to common questions about lactose intolerance, research news, nutrition information, and more.


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