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Lactose Intolerance

Lactose intolerance is condition in which a person is unable to digest a lot of lactose due to a lack of the enzyme lactase. Lactose intolerance symptoms can be cramps, bloating and diarrhea.


  • Lactose intolerance is when you are not able to digest a lot of lactose, which is the main sugar in milk. 
  • Lactose intolerance results from a shortage of the enzyme lactase, which is normally made by the cells that line the small gut. Lactase breaks down the sugar in milk into simpler forms so it can then be pulled into the blood stream.
  • Symptoms start about 30 minutes to two hours after eating or drinking foods that have lactose (mainly milk products). The harshness of symptoms varies based on the amount of lactose you are able to handle.
  • For most people, lactose intolerance develops over time.
  • Symptoms may start years after childhood.
  • Close to 50 million adults in the U.S. are lactose intolerant.
  • Lactose intolerance is usually caused by genes, meaning you are born with it, and it doesn’t go away.
  • Sometimes lactose intolerance is brought on by something else, such as a virus or infection that causes temporary damage to the small intestine. Once your gut is healed from these other causes, you are often able to consume lactose again.

Common symptoms

Symptoms of lactose intolerance are not the same for each person. Some common symptoms are:
  • Upset belly.
  • Cramps.
  • Bloating.
  • Gas.
  • Diarrhea (loose stool).
Getting Tested

Getting Tested

Lactose intolerance can be hard to figure out based just on symptoms. A gastroenterologist can use tests to find out if you’re lactose intolerant:
Lactose Breath Test
  • Given to older children as well as adults.*
  • This test measures the amount of hydrogen in the breath. This test is very accurate.
  • In the test, the patient drinks a lactose-loaded drink, and the breath is tested at routine intervals.
  • Hydrogen in the breath means improper digestion of lactose.
  • Certain foods, medications and smoking can change the test’s accuracy and may need to be skipped before the test.
Stool Acidity Test
  • Used for infants and young children.
  • This test, which measures the amount of acid in the stool, has no risk to young children.
  • This test is not very specific.
Lactose Tolerance Test
  • This test is not often used. This test may be performed if the lactose breath test is not available.
  • Given to older children as well as adults.*
  • Before the test, patients do not eat, and blood is taken to measure the fasting blood-sugar level.
  • Patients then drink a large amount of a liquid that has lactose.
  • Blood samples are taken over a two-hour period, which tell how well the body is able to digest lactose.
* The lactose tolerance and hydrogen breath tests are not given to infants and young children, because giving these patients a lactose load can result in diarrhea (loose stool), which can cause dehydration.
Controlling Symptoms

Controlling Symptoms

Being diagnosed with a food intolerance and needing to change how you eat, can feel like a lot to take on. While it is not as severe as having a food allergy, a food intolerance can impact your life.  You might be scared to eat for fear of having a reaction. You may not want to join your family and friends when they go out, because you’re worried about cross-contamination. These feelings are normal and can be handled by talking to your gastroenterologist and a registered dietician or nutritionist.  By learning more about what a food intolerance means for you, you’ll feel more in control and better able to manage the changes.
  • Symptoms of lactose intolerance can be controlled through diet.
  • Many older children and adults do not need to avoid lactose entirely, but people differ in the amounts of lactose they can handle. This means you need to figure out, through trial and error, how much lactose you can handle.
  • There are some products to help control symptoms:
    • Lactase enzyme: These help people digest solid foods that have lactose; enzymes are taken just before a meal or snack and can come in tablet, chewable or liquid form.
    • Lactose-free milk and other products: These are found at most supermarkets; the milk has all of the other nutrients found in normal milk and stays fresh for about the same length of time. Examples are soy or almond milk. Also, hard cheeses like blocks of parmesan often have no lactose.

Watching for hidden lactose

Though milk and foods made from milk are the only noteworthy natural sources, lactose is often added to prepared foods. It is vital for people with very low tolerance for lactose to know about the many foods that have lactose, even in small amounts. Be sure to read all labels.  Some common items that have lactose are:

  • Bread and other baked goods.
  • Processed breakfast cereals.
  • Instant potatoes, soups and breakfast drinks.
  • Margarine.
  • Lunch meats (other than kosher).
  • Salad dressings.
  • Candies and other snacks.
  • Mixes for pancakes, biscuits and cookies.
  • Powdered meal-replacement supplements.
  • Some “nondairy” products, such as powdered coffee creamer and whipped topping, may have parts that are derived from milk and therefore have lactose.
  • Lactose is used as the base for more than 20 percent of medications and about 6 percent of over-the-counter (OTC) drugs. Many types of birth control pills have lactose, as do some tablets for stomach acid and gas. A pharmacist can answer questions about the amounts of lactose in certain meds.

Reading food labels

If any of these items are on a food label, it may have lactose:
  • Milk.
  • Lactose.
  • Whey.
  • Milk by-products.
  • Dry milk solids.
  • Non-fat dry milk powder.

Getting appropriate nutrition

Milk and other dairy products are a major source of nutrients, like calcium and vitamin D, in a balanced diet. Calcium is needed for the growth and repair of bones throughout life. As you remove milk and dairy items from your diet, be sure to get extra calcium in other ways.  The table below shows how much calcium you should be getting each day and some ideas on how to get it. Food and Nutrition Board, Institute of Medicine, National Academics Dietary Reference Intakes: Estimated Average Requirement of Calcium Intake Per Day (in mg)
Age Male (mg of calcium/day) Female (mg of calcium/day)
1 to 3 years 500 500
4 to 8 years 800 800
9 to 13 years 1,100 1,100
14 to 18 years 1,000 1,000
19 to 30 years 800 800
31 to 50 years 800 800
51 to 70 years 800 800
>70 years 1,000 1,000
It is important in meal planning to make sure that each day’s food has enough calcium, even if your diet does not have dairy products. Many foods are high in calcium but do not have lactose, including:

  • Firm tofu with calcium sulfate (3.5 oz: 683 mg calcium).
  • Soy milk (1 cup: 200–300 mg calcium).
  • Sardines, with edible bones (3 oz: 382 mg calcium).
  • Salmon, canned with edible bones (3 oz: 198 mg calcium).
  • Broccoli (1 cup: 90 mg calcium).
  • Oranges (1 medium: 50 mg calcium).
  • Pinto beans (1/2 cup: 40 mg calcium).
  • Tuna, canned (3 oz.: 10 mg calcium).
  • Lettuce greens (1/2 cup: 10 mg calcium).
Dairy products that are high in calcium and low in lactose (meaning there is some lactose, so they can be consumed by people who can handle a little bit of lactose) include:
  • Plain, low-fat yogurt (1 cup: 415 mg calcium, 5 g lactose).
  • Reduced-fat milk (1 cup: 295 mg calcium, 11 g lactose).
  • Swiss cheese (1 oz.: 279 mg calcium, 1 g lactose).
  • Ice cream (1/2 cup: 85 mg calcium, 6 g lactose).
  • Cottage cheese (1/2 cup: 75 mg calcium, 2–3 g lactose).
If you have symptoms from dairy fat, you could also try hard cheeses that are low in fat as well as a source of calcium. Adapted from Manual of Clinical Dietetics. 6th ed. American Dietetic Association, 2000; and Soy Dairy Alternatives.

Still having symptoms?

It can be scary to keep having symptoms, even after changing to a low-lactose or lactose-free diet. If this is the case for you, perhaps you are eating hidden lactose. A dietitian can help you find out if you are unintentionally consuming lactose through such things as medications, supplements or other sources. If you are eating a strict lactose-free diet, and are sure you aren’t consuming hidden lactose, your doctor should think about testing you for other causes of your symptoms (such as celiac disease or Crohn’s disease) to make sure nothing else is going on. Try the MyGIHealth® app to better note your symptoms and when they happen.

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