What Is Lactose Intolerance?

Lactose Intolerance Is Very Common And Treatment Includes Avoiding Milk Products

Melted ice cream cone

Verywell / Zorica Lakonic

Lactose intolerance is a common problem. Learn more about what causes lactose intolerance, its symptoms, and how you can manage it.

What Is Lactose Intolerance?

Lactose intolerance is caused by the body's inability to digest milk sugar, or lactose. In order to break lactose down into simple sugars, or monosaccharides, the body must produce the enzyme called "lactase," which is produced in the small intestine. Without lactase, the lactose from milk products is unable to be digested. This causes the symptoms of gas, cramps and diarrhea that many people experience after eating or drinking dairy products.

Lactose intolerance is a condition that normally develops over time. After a person reaches about 2 years of age, the body begins to produce less of the enzyme lactase. The reasons for this are not understood. It is rare for an infant to be born lactose intolerant, which can cause vomiting and a "failure to thrive." Symptoms of lactose intolerance can appear years after childhood.

The good news is that there are many products on the market today that can treat lactose intolerance or prevent it altogether. For every type of dairy, there's a substitute available, and manufacturers have gotten very skilled at making non-dairy foods that taste like the original.


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Who Gets Lactose Intolerance?

Experts estimate that as many as 50 million American adults are lactose intolerant. Lactose intolerance primarily affects people of Chinese, Korean, Japanese, Jewish and African descent. People of northern European and some Middle Eastern (Bedouins, Saudis, Yemenis) descents have little incidence of lactose intolerance. Geographical regions seem to play a role in the incidence of lactose intolerance. Descendants of people from northern Europe, for example, have been dependent on milk products as a food source in their geographic region for a few thousand years. Ethnicities that have a higher percentage of adults with lactose intolerance have not been dependent on milk products in the geographic regions of their ancestors.

What to know about lactose intolerance

Verywell / Ellen Lindner


Symptoms of lactose intolerance can include gas, diarrhea, bloating, cramps, nausea and bad breath. These symptoms can begin anywhere from 30 minutes to 2 hours after ingesting lactose and can last for up to 3 days after. The severity of symptoms varies from person to person and is dependent upon the amount of lactose that can be tolerated.

What Does Lactose Intolerance Have to Do With IBD?

Many people with inflammatory bowel disease (IBD) also suffer from lactose intolerance. The symptoms of gas, bloating and diarrhea caused by IBD are compounded by the same symptoms caused by lactose intolerance.


There are three tests most commonly used to diagnose lactose intolerance: the lactose tolerance test, the hydrogen breath test and the stool acidity test.

The lactose tolerance test. This test is appropriate for both older children and adults. Patients will fast for several hours before the test begins. Blood is drawn to measure the current blood glucose level. Next, the patient will drink a liquid that contains up to 50 grams of lactose. For the next two hours, more blood samples are taken to measure blood glucose levels. If the lactose is being broken down in the body by the enzyme lactase, the blood glucose level will rise. If the blood glucose level does not rise, that means that the lactose is not being broken down into simple sugars and the patient has lactose intolerance.

The hydrogen breath test. This test is very similar to the lactose intolerance test and might be done on children as young as 6 months as well as adults. After fasting for several hours, the patient will exhale in to a mouthpiece connected to a foil bag that looks like a balloon. This bag is to be used as a comparison for the second part of the test. Next, the patient will drink a liquid that can contain up to 50 grams of lactose. More breath samples will be taken at various intervals for up to 6 hours.

Normally, there is no hydrogen present in a person's breath. When a lactose intolerant person ingests lactose, it stays in their intestines and ferments, ultimately producing hydrogen gas. Therefore, if hydrogen is present in the breath samples taken after drinking the lactose, the diagnosis of lactose intolerance can be made.

The stool acidity test. This test is normally done on infants and small children. It is noninvasive and presents no problems, such as dehydration caused by diarrhea, from ingesting large amounts of lactose. A stool sample is collected and tested for lactic acid, glucose and other short-chain fatty acids that may be present when lactose remains undigested by the body.


Lactose intolerance is most often controlled through adjustments to the diet. For small children, all foods that contain lactose should be avoided. For adults and older children, the amount of lactose that can be tolerated will vary. Some people may be able to eat butter and aged cheeses, which have low levels of lactose, while others may find one glass of milk won't bother them, but two will. Only through trial and error can people with lactose intolerance discover the type and amounts of dairy products that are tolerated.

Tips for reducing dairy intake:

  • Eat foods that contain lactose with other foods
  • Read food labels carefully
  • Eat smaller portions of foods that contain lactose
  • Try a milk substitute (soy or rice milk)
  • Try yogurts with "live cultures;" they may be better tolerated

If avoiding dairy is a problem, there are several commercial products available that contain the enzyme lactase. These products come in different varieties. One type is a liquid drop that can be added to milk to break down the lactose content. The lactose can be reduced anywhere from 70 to 90%. Another is in a pill form that's swallowed just before or with the first bite of dairy. Still more are chewable tablets that are also taken at the beginning of a meal containing dairy. Lactose reduced milk, ice cream, cheeses and other dairy products are also readily available.

Watch That "Hidden" Lactose!

Be on the lookout for hidden lactose. Up to 20% of medications use lactose as a base. Your pharmacist will know which ones. Read food labels carefully, because foods containing whey, curds, milk by-products, dry milk solids and nonfat dry milk powder will contain lactose. Other foods that may contain lactose are:

  • Bread and other baked goods
  • Breakfast drinks
  • Candies and snacks
  • Chewing gum
  • Commercial pie crusts
  • Cookies and sandwich cookie fillings
  • Cream cordials and liquors
  • Creamed vegetables
  • Dips
  • French fries (lactose is a browning agent)
  • Instant coffee (with sugar, creamer, flavoring)
  • Instant potatoes
  • Lunch meats
  • Margarine
  • Pancakes, biscuits and cookie mixes
  • Powdered coffee creamers
  • Processed breakfast cereals
  • Pudding and mixes
  • Salad dressings
  • Soups

But Don't I Need To Get Calcium From Milk?

Daily Calcium Guidelines

  • Infants to 6 months: 210 mg
  • 6 to 11 months: 270 mg
  • 1 to 3 years old: 500 mg
  • 4- to 8-years-olds : 800 mg
  • 9- to 18-years-olds: 1,300 mg
  • 19- to 50-year-olds: 1,300 mg
  • 51 and older: 1200 mg
  • 50-year-old women and older not taking HRT: 1,500 mg
  • Pregnant and nursing women: 1,000 mg (younger than 18 years old: 1,300 mg)

Calcium, as we all know from the famous commercials, is necessary for "strong bones and healthy teeth." Women and girls, in particular, need to make sure they get the proper amount of calcium every day.

People avoiding or cutting back on dairy foods need to get their calcium from other sources. Fortunately, drinking a glass of milk is not the only way to get calcium! A physician or nutritionist may recommend a daily calcium supplement. There are numerous varieties of supplements, and enlisting the help of a healthcare professional to choose the appropriate one is essential. For those who would like to get calcium from a food source, I have listed below several foods that have significant amounts of calcium, yet are nondairy.

The Bottom Line

There are many myths, fallacies and controversies surrounding dairy and lactose intolerance. It's not known why our bodies stop being able to digest milk sugars, but we do know the result can be embarrassing and distressing. The best way to combat lactose intolerance is to be armed with knowledge about what foods cause symptoms and how to avoid them.

Non-dairy calcium-rich foods

Vegetables Calcium
Broccoli (pieces cooked),1 cup 94-177 mg 0
Chinese cabbage (
bok choy, Cooked), 1cup
158 mg 0
Collard greens (cooked), 1 cup 148-357 mg 0
Kale (cooked), 1 cup 94-179 mg 0
Turnip greens (cooked), 1 cup 194-249 mg 0
Fish/Seafood Calcium
Oysters (raw), 1 cup 226 mg 0
Salmon with bones (canned), 3 oz 167 mg 0
Sardines, 3 oz 371 mg 0
Shrimp (canned), 3 oz 98 mg 0
Other Calcium
Molasses, 2 tbsp 274 mg 0
Tofu (processed with Calcium salts, 3 oz 225 mg 0
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Additional Reading

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.