Lactose intolerance means the body cannot easily digest lactose, a type of natural sugar found in milk and dairy products. This is not the same thing as a food allergy to milk.
When lactose moves through the large intestine (colon) without being properly digested, it can cause uncomfortable symptoms such as gas, belly pain, and bloating. Some people who have lactose intolerance cannot digest any milk products. Others can eat or drink small amounts of milk products or certain types of milk products without problems.
Lactose intolerance is common in adults. It occurs more often in Native Americans and people of Asian, African, and South American descent than among people of European descent.
A big challenge for people who are lactose-intolerant is learning how to eat to avoid discomfort and to get enough calcium for healthy bones.
What causes lactose intolerance?
Lactose intolerance occurs when the small intestine does not make enough of an enzyme called lactase. Your body needs lactase to break down, or digest, lactose.
Lactose intolerance most commonly runs in families, and symptoms usually develop during the teen or adult years. Most people with this type of lactose intolerance can eat some milk or dairy products without problems.
Sometimes the small intestine stops making lactase after a short-term illness such as the stomach flu or as part of a lifelong disease such as cystic fibrosis. Or the small intestine sometimes stops making lactase after surgery to remove a part of the small intestine. In these cases, the problem can be either permanent or temporary.
In rare cases, newborns are lactose-intolerant. A person born with lactose intolerance cannot eat or drink anything with lactose.
Some premature babies have temporary lactose intolerance because they are not yet able to make lactase. After a baby begins to make lactase, the condition typically goes away.
What are the symptoms?
Symptoms of lactose intolerance can be mild to severe, depending on how much lactase your body makes. Symptoms usually begin 30 minutes to 2 hours after you eat or drink milk products. If you have lactose intolerance, your symptoms may include:
Bloating.
Pain or cramps.
Gurgling or rumbling sounds in your belly.
Gas.
Loose stools or diarrhea.
Throwing up.
Many people who have gas, belly pain, bloating, and diarrhea suspect they may be lactose-intolerant. The best way to check this is to avoid eating all milk and dairy products to see if your symptoms go away. If they do, then you can try adding small amounts of milk products to see if your symptoms come back.
If you feel sick after drinking a glass of milk one time, you probably do not have lactose intolerance. But if you feel sick every time you have milk, ice cream, or another dairy product, you may have lactose intolerance.
Sometimes people who have never had problems with milk or dairy products suddenly have lactose intolerance. This is more common as you get older.
If you think you might have lactose intolerance, talk with your doctor. He or she can make sure that your symptoms are caused by lactose intolerance and not by another problem.
How is lactose intolerance diagnosed?
A doctor can usually tell whether you have lactose intolerance by asking questions about your symptoms. He or she may also ask that you avoid dairy products for a short time to see if your symptoms improve.
Sometimes doctors order a hydrogen breath test or a blood sugar test to confirm the diagnosis. These simple tests check to see if you are digesting lactose normally.
How is it treated?
There is no cure for lactose intolerance. But you can treat your symptoms by limiting or avoiding milk products. Some people use milk with reduced lactose, or they substitute soy milk and soy cheese for milk and milk products. Some people who are lactose-intolerant can eat yogurt without problems, especially yogurt with live cultures. You can also take dietary supplements called lactase products that help digest lactose. In time, most people who have lactose intolerance get to know their bodies well enough to avoid symptoms.
One of the biggest concerns for people who are lactose-intolerant is making sure they get enough of the nutrients found in milk products, especially calcium. Calcium is most important for children, teens, pregnant women, and women after menopause. There are many nondairy foods that contain calcium, including:
Broccoli, okra, kale, collards, and turnip greens.
Canned sardines, tuna, and salmon.
Calcium-fortified juices and cereals.
Calcium-fortified soy products such as soy milk, tofu, and soybeans.
Almonds.
Symptoms
Symptoms of lactose intolerance can be mild or severe, depending on how much lactase your body makes. Symptoms usually begin 30 minutes to 2 hours after eating or drinking milk or milk products. If you have lactose intolerance, your symptoms may include:
Bloating.
Pain or cramps in the lower belly.
Gurgling or rumbling sounds in the lower belly.
Gas.
Loose stools or diarrhea. Sometimes the stools are foamy.
Throwing up.
Many people think they are lactose-intolerant, because the symptoms of lactose intolerance are very common symptoms. If you feel sick after drinking a glass of milk one time, you probably do not have lactose intolerance. But if you feel sick every time you have milk, ice cream, or another dairy product, you may have lactose intolerance.
Sometimes people who have never had problems with milk or dairy products suddenly have lactose intolerance. This is more common as you get older.
Symptoms of the most common type of lactose intolerance-adult lactose intolerance-often start during the teen or adult years and continue for life. Symptoms of acquired lactose intolerance last as long as the small intestine does not make lactase.
In rare cases, newborns are lactose-intolerant. Symptoms in newborns include severe foamy diarrhea, diaper rash, vomiting, dehydration, weakness and irritability, and slow weight gain.
Lactose intolerance is not the same thing as a food allergy to milk. Symptoms of a milk allergy are usually more severe than those from lactose intolerance. People who have a milk allergy cannot eat or drink any milk products. For more information, see the topic Food Allergies.
If you think you might have lactose intolerance, talk it over with your doctor. Your doctor can make sure that your symptoms are caused by lactose intolerance and not by another problem. Other conditions can cause symptoms similar to those of lactose intolerance, including irritable bowel syndrome, inflammatory bowel disease, overuse of laxatives, and problems digesting foods that contain fructose and sorbitol.
Exams and Tests
If your doctor thinks you have lactose intolerance, he or she will ask questions about your medical history and do a physical exam. Before making a diagnosis, your doctor may ask that you avoid dairy products for a short time to see if your symptoms improve. You may also be asked to bring in a sample of your stool. The stool of a person who has lactose intolerance is usually loose or watery. It also can be foamy.
To confirm a diagnosis, your doctor may order a:
Hydrogen breath test. This is the most accurate lactose intolerance test. Before the test, you need to avoid certain foods and medicines and cigarettes. On the day of the test, you will drink a liquid that contains lactose and then breathe into a machine several times over a couple of hours. If the hydrogen levels in your breath are high, you may have lactose intolerance. This test is not usually done on babies and very young children, because it can cause severe diarrhea.
Lactose tolerance test. This test measures your blood sugar after you eat or drink lactose. After midnight on the night before the test, you should not eat or drink anything. On the day of your test, you will drink a liquid that contains lactose, which may cause gas or pain in your belly. Then your blood will be tested every 30 minutes for 2 hours. If your blood sugar levels do not rise, you may be lactose-intolerant. This test is not done on people who have diabetes. And it is usually not done on babies and very young children.
Treatment Overview
If you think you have lactose intolerance, it is a good idea to talk it over with your doctor. Your doctor can make sure that your symptoms are caused by lactose intolerance and not by another problem such as irritable bowel syndrome, inflammatory bowel disease, overuse of laxatives, or problems digesting foods that contain fructose or sorbitol. Your doctor can also make sure that your lactose intolerance is not related to another health problem.
After being diagnosed with lactose intolerance, you may feel relieved to find out what has been causing your symptoms. You may also feel frustrated by having to deal with this condition for the rest of your life. You may find it reassuring to know that there are many people who have lactose intolerance. Most can avoid discomfort and still eat or drink some milk products throughout the day.
There are different ways to live with lactose intolerance. What works for one person may not work for another. Because there is no cure for lactose intolerance, controlling your symptoms is mostly up to you. The following tips can help you prevent symptoms of lactose intolerance.
Limit the amount of milk and milk products in your diet. Most people can have about 10 g of lactose each day. This can be a glass of whole, low-fat, or fat-free milk, for example. All milk contains the same amount of lactose. Other milk products contain different amounts of lactose:
Approximate lactose and calcium in some foodsfootnote 1
Food
Serving size
Lactose (g)
Calcium (mg)
Milk, fat-free
8 fl oz (240 mL)
12.5
300
Cheddar cheese
1 oz (30 g)
0.15
204
Cottage cheese, 2% milk fat
4 oz (113 g)
4.15
100
Cream cheese
1 oz (30 g)
0.9
28
Foods with less lactose, such as Swiss or cheddar cheese, may not cause problems. If you are not sure whether a milk product causes symptoms, try a small amount and wait to see how you feel before you eat or drink more.
Eat or drink milk and milk products along with other foods. For some people, combining a solid food (like cereal) with a dairy product (like milk) may reduce or eliminate symptoms.
Spread milk or milk products throughout the day. Many people who are lactose-intolerant find it helpful to eat small amounts of lactose-containing products throughout the day instead of larger amounts all at one time.
Eat or drink milk and milk products that have reduced lactose. In most grocery stores, you can buy milk with reduced lactose. Some people like buying this kind of milk and find that it helps control their symptoms. Others find that it tastes too sweet or is too expensive. People who have diabetes may find that lactose-reduced milk raises their blood sugar levels higher than normal.
Eat or drink other foods instead of milk and milk products.You can substitute soy milk and soy cheese for milk and milk products. You can also use nondairy creamers in your coffee. But keep in mind that nondairy creamers do not contain the same vitamins and minerals as milk, and they may contain more fat than milk contains.
Use lactase products. Lactase products are dietary supplements that help you digest lactose. There are many different brands of lactase products. Some are pills that you chew (such as Lactaid) before you eat or drink milk products. Others are liquids that you can add to milk 24 hours before you drink it. Some foods have extra lactase added to them. Because products and brands are different, you may want to try a few to see which ones work best for you.
Eat yogurt with live and active cultures. Some people who are lactose-intolerant can eat yogurt without having problems, especially yogurt that contains live and active cultures. This type of yogurt can help people digest lactose. All yogurts are made with live cultures, but many yogurts go through a process called "heat treatment" that kills the bacteria. Check the label for the words "contains live and active cultures." It's best to try a small amount of different brands of yogurt to see which ones work best for you.
If you have severe lactose intolerance, you may need to avoid lactose completely. Some medicines and many prepared foods contain lactose. Examples of prepared foods with lactose include breads and baked goods; breakfast cereals and instant breakfast drinks; instant potatoes and instant soups; pancake, cookie, and biscuit mixes; margarine and salad dressings; candies, milk chocolate, and other snacks. Be sure to read labels for lactose and for lactose's "hidden" names, such as:
Dry milk solids.
Whey.
Curds.
Milk by-products.
Nonfat dry milk powder.
One of the biggest concerns for people who are lactose-intolerant is making sure they get enough of the nutrients found in milk products, especially calcium. Calcium is especially important for women, because it keeps bones strong and reduces the risk of osteoporosis. There are many nondairy foods that contain calcium, including:
Broccoli, okra, kale, collards, and turnip greens.
Canned sardines, tuna, and salmon.
Calcium-fortified juices and cereals.
Calcium-fortified soy products such as soy milk, tofu, and soybeans.
Almonds.
To absorb calcium, your body needs vitamin D. Most people get enough vitamin D by being out in the sun for short periods of time each day. Vitamin D is also found in fortified orange juice, fortified soy milk, oily fish (such as salmon), egg yolks, and liver.
If you don't know whether you are getting enough calcium, vitamin D, and other important nutrients found in milk products, such as magnesium, potassium, protein, and riboflavin, talk to your doctor. He or she may recommend that you take a calcium supplement or meet with a registered dietitian to make sure you are getting enough of certain vitamins and minerals.
You should also talk with your doctor if your symptoms do not go away with treatment, if they get worse, or if you have other symptoms, such as a fever, chills, or severe belly pain or vomiting.
What to think about
Lactose intolerance in newborns of normal birth weight and in babies is rare. But if your child has symptoms of lactose intolerance, see your doctor right away. Diarrhea is very dangerous because it can lead to dehydration, a serious problem that requires immediate attention.
Babies who are only fed breast milk do not develop lactose intolerance, because breast milk contains lactase, the enzyme that helps digest milk sugar. If your baby is formula-fed and develops lactose intolerance, you can switch to a formula made without lactose. In rare cases, a baby may have a reaction to the proteins in milk, which is a different condition called sensitivity to milk protein.
U.S. Department of Agriculture, Agricultural Research Service (2012). Nutrient data laboratory. USDA National Nutrient Database for Standard Reference, Release 25. Available online: http://ndb.nal.usda.gov.
Other Works Consulted
American Academy of Pediatrics (2014). Carbohydrate and dietary fiber. In Pediatric Nutrition, 7th ed., pp. 387-406. Elk Grove Village, IL: American Academy of Pediatrics.
Hogenauer C, Hammer HF (2010). Maldigestion and malabsorption. In M Feldman et al., eds., Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 9th ed., vol. 2, pp. 1735-1767. Philadelphia: Saunders.
Whitney E, Rolfes SR (2011). Digestion and absorption of carbohydrates section of The carbohydrates: Sugars, starches, and fibers. In Understanding Nutrition, 12th ed., pp. 105-107. Belmont, CA: Wadsworth.
Credits
ByHealthwise Staff Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine Adam Husney, MD - Family Medicine John Pope, MD, MPH - Pediatrics Martin J. Gabica, MD - Family Medicine Kathleen Romito, MD - Family Medicine Rohit K. Katial, MD - Allergy and Immunology
U.S. Department of Agriculture, Agricultural Research Service (2012). Nutrient data laboratory. USDA National Nutrient Database for Standard Reference, Release 25. Available online: http://ndb.nal.usda.gov.
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