Lactose intolerance means that you cannot digest foods with lactose in them. Lactose is the sugar found in milk and foods made with milk. After eating foods with lactose in them, you may feel sick to your stomach. You may also have

• Gas
• Diarrhea
• Swelling in your stomach

Your doctor may do a blood, breath or stool test to find out if your problems are due to lactose intolerance.

Lactose intolerance is not serious. Eating less food with lactose, or using pills or drops to help you digest lactose usually helps. You may need to take a calcium supplement if you don't get enough of it from your diet, since milk and foods made with milk are the most common source of calcium for most people.

Lactose intolerance is a condition in which you have digestive symptoms—such as bloating, diarrhea, and gas—after you consume foods or drinks that contain lactose. Lactose is a sugar that is naturally found in milk and milk products, like cheese or ice cream.

In lactose intolerance, digestive symptoms are caused by lactose malabsorption. Lactose malabsorption is a condition in which your small intestine cannot digest, or break down, all the lactose you eat or drink.

Not everyone with lactose malabsorption has digestive symptoms after they consume lactose. Only people who have symptoms are lactose intolerant.

Most people with lactose intolerance can consume some amount of lactose without having symptoms. Different people can tolerate different amounts of lactose before having symptoms.

Lactose intolerance is different from a milk allergy. A milk allergy is an immune system disorder.

Lactose intolerance and milk allergies are different conditions with different causes. Lactose intolerance is caused by problems digesting lactose, the natural sugar in milk. In contrast, milk allergies are caused by your immune system’s response to one or more proteins in milk and milk products.

A milk allergy most often appears in the first year of life, while lactose intolerance typically appears later. Lactose intolerance can cause uncomfortable symptoms, while a serious allergic reaction to milk can be life threatening.

Congenital lactase deficiency is a rare disorder, though its exact incidence is unknown. This condition is most common in Finland, where it affects an estimated 1 in 60,000 newborns.

Approximately 65 percent of the human population has a reduced ability to digest lactose after infancy. Lactase nonpersistence is most prevalent in people of East Asian descent, with 70 to 100 percent of people affected in these communities. Lactase nonpersistence is also very common in people of West African, Arab, Jewish, Greek, and Italian descent.

The prevalence of lactose intolerance is lowest in populations with a long history of dependence on unfermented milk products as an important food source. For example, only about 5 percent of people of Northern European descent are lactase nonpersistent.

You are more likely to have lactose intolerance if you are from, or your family is from, a part of the world where lactose malabsorption is more common. In the United States, the following ethnic and racial groups are more likely to have lactose malabsorption:

• African Americans
• American Indians
• Asian Americans
• Hispanics/Latinos

Because these ethnic and racial groups are more likely to have lactose malabsorption, they are also more likely to have the symptoms of lactose intolerance.

Lactose intolerance is least common among people who are from, or whose families are from, Europe.

Lactose intolerance is caused by lactose malabsorption. If you have lactose malabsorption, your small intestine makes low levels of lactase—the enzyme that breaks down lactose—and can’t digest all the lactose you eat or drink.

The undigested lactose passes into your colon. Bacteria in your colon break down the lactose and create fluid and gas. In some people, this extra fluid and gas causes lactose intolerance symptoms.

In some cases, your genes are the reason for lactose intolerance. Genes play a role in the following conditions, and these conditions can lead to low levels of lactase in your small intestine and lactose malabsorption:

• Lactase nonpersistence. In people with lactase nonpersistence, the small intestine makes less lactase after infancy. Lactase levels get lower with age. Symptoms of lactose intolerance may not begin until later childhood, the teen years, or early adulthood. Lactase nonpersistence, also called primary lactase deficiency, is the most common cause of low lactase levels.
• Congenital lactase deficiency. In this rare condition, the small intestine makes little or no lactase, starting at birth.

Not all causes of lactose intolerance are genetic. The following can also lead to lactose intolerance:

• Injury to the small intestine. Infections, diseases, or other conditions that injure your small intestine, like Crohn’s disease or celiac disease, may cause it to make less lactase. Treatments—such as medicines, surgery, or radiation therapy—for other conditions may also injure your small intestine. Lactose intolerance caused by injury to the small intestine is called secondary lactose intolerance. If the cause of the injury is treated, you may be able to tolerate lactose again.
• Premature birth. In premature babies, or babies born too soon, the small intestine may not make enough lactase for a short time after birth. The small intestine usually makes more lactase as the baby gets older.

While most infants can digest lactose, many people begin to develop lactose malabsorption—a reduced ability to digest lactose—after infancy. Experts estimate that about 68 percent of the world’s population has lactose malabsorption.

Lactose malabsorption is more common in some parts of the world than in others. In Africa and Asia, most people have lactose malabsorption. In some regions, such as northern Europe, many people carry a gene that allows them to digest lactose after infancy, and lactose malabsorption is less common. In the United States, about 36 percent of people have lactose malabsorption.

While lactose malabsorption causes lactose intolerance, not all people with lactose malabsorption have lactose intolerance.

Congenital lactase deficiency is caused by variants (also called mutations) in the LCT gene. The LCT gene provides instructions for making the lactase enzyme. Variants in the LCT gene that cause congenital lactase deficiency are believed to interfere with the processing and function of lactase, causing affected infants to have a severely impaired ability to digest the lactose in breast milk or formula.

Lactase nonpersistence in adulthood is caused by the gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans. LCT gene expression is controlled by a DNA sequence called a regulatory element, which is located within a nearby gene called MCM6. Some individuals have inherited changes in this element that lead to sustained lactase production in the small intestine and the ability to digest lactose throughout life. People without these changes have a reduced ability to digest lactose as they get older, resulting in the signs and symptoms of lactase nonpersistence.

Congenital lactase deficiency is inherited in an autosomal recessive pattern, which means both copies of the LCT gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

The ability to digest lactose into adulthood depends on which variants in the regulatory element within the MCM6 gene individuals have inherited from their parents. The variants that promote continued lactase production are considered autosomal dominant, which means one copy of the altered regulatory element in each cell is sufficient to sustain lactase production. People who have not inherited these variants from either parent are lactase nonpersistent and will have some degree of lactose intolerance.

If you have lactose intolerance, you may have symptoms within a few hours after you have milk or milk products, or other foods that contain lactose. Your symptoms may include

• bloating
• diarrhea
• gas
• nausea
• pain in your abdomen
• stomach “growling” or rumbling sounds
• vomiting

Your symptoms may be mild or severe, depending on how much lactose you have.

To diagnose lactose intolerance, your doctor will ask about your symptoms, family and medical history, and eating habits.

Your doctor may perform a physical exam and tests to help diagnose lactose intolerance or to check for other health problems. Other conditions, such as irritable bowel syndrome, celiac disease, inflammatory bowel disease, or small bowel bacterial overgrowth can cause symptoms similar to those of lactose intolerance.

Your doctor may ask you to stop eating and drinking milk and milk products for a period of time to see if your symptoms go away. If your symptoms don’t go away, your doctor may order additional tests.

Physical exam

During a physical exam, your doctor may

• check for bloating in your abdomen
• use a stethoscope to listen to sounds within your abdomen
• tap on your abdomen to check for tenderness or pain

Your doctor may order a hydrogen breath test to see how well your small intestine digests lactose.

Hydrogen breath test

Doctors use this test to diagnose lactose malabsorption and lactose intolerance. Normally, a small amount of hydrogen, a type of gas, is found in your breath. If you have lactose malabsorption, undigested lactose causes you to have high levels of hydrogen in your breath.

For this test, you will drink a liquid that contains a known amount of lactose. Every 30 minutes over a few hours, you will breathe into a balloon-type container that measures the amount of hydrogen in your breath. During this time, a health care professional will ask about your symptoms. If both your breath hydrogen levels rise and your symptoms get worse during the test, your doctor may diagnose lactose intolerance.

Treatments depend on the cause of lactose intolerance. If your lactose intolerance is caused by lactase nonpersistence or congenital lactase deficiency, no treatments can increase the amount of lactase your small intestine makes. Your doctor can help you change your diet to manage your symptoms.

If your lactose intolerance is caused by an injury to your small intestine, your doctor may be able to treat the cause of the injury. You may be able to tolerate lactose after treatment.

While some premature babies are lactose intolerant, the condition usually improves without treatment as the baby gets older.

In most cases, you can manage the symptoms of lactose intolerance by changing your diet to limit or avoid foods and drinks that contain lactose, such as milk and milk products.

Some people may only need to limit the amount of lactose they eat or drink, while others may need to avoid lactose altogether. Using lactase products can help some people manage their symptoms.

Lactase products

Lactase products are tablets or drops that contain lactase, the enzyme that breaks down lactose. You can take lactase tablets before you eat or drink milk products. You can also add lactase drops to milk before you drink it. The lactase breaks down the lactose in foods and drinks, lowering your chances of having lactose intolerance symptoms.

Check with your doctor before using lactase products. Some people, such as young children and pregnant and breastfeeding women, may not be able to use them.

Talk with your doctor or a dietitian about changing your diet to manage lactose intolerance symptoms while making sure you get enough nutrients. If your child has lactose intolerance, help your child follow the dietary plan recommended by a doctor or dietitian.

To manage your symptoms, you may need to reduce the amount of lactose you eat or drink. Most people with lactose intolerance can have some lactose without getting symptoms.

Foods that contain lactose

You may not need to completely avoid foods and beverages that contain lactose—such as milk or milk products. If you avoid all milk and milk products, you may get less calcium and vitamin D than you need.

People with lactose intolerance can handle different amounts of lactose. Research suggests that many people could have 12 grams of lactose—the amount in about 1 cup of milk—without symptoms or with only mild symptoms.

You may be able to tolerate milk and milk products if you

• drink small amounts of milk at a time and have it with meals
• add milk and milk products to your diet a little at a time and see how you feel
• try eating yogurt and hard cheeses, like cheddar or Swiss, which are lower in lactose than other milk products
• use lactase products to help digest the lactose in milk and milk products

Lactose-free and lactose-reduced milk and milk products

Using lactose-free and lactose-reduced milk and milk products may help you lower the amount of lactose in your diet. These products are available in many grocery stores and are just as healthy for you as regular milk and milk products.

Calcium and Vitamin D

If you are lactose intolerant, make sure you get enough calcium and vitamin D each day. Milk and milk products are the most common sources of calcium.

Many foods that do not contain lactose are also sources of calcium. Examples include:

• fish with soft bones, such as canned salmon or sardines
• broccoli and leafy green vegetables
• oranges
• almonds, Brazil nuts, and dried beans
• tofu
• products with labels that show they have added calcium, such as some cereals, fruit juices, and soy milk

Vitamin D helps your body absorb and use calcium. Be sure to eat foods that contain vitamin D, such as eggs and certain kinds of fish, such as salmon. Some ready-to-eat cereals and orange juice have added vitamin D. Some milk and milk products also have added vitamin D. If you can drink small amounts of milk or milk products without symptoms, choose products that have added vitamin D. Also, being outside in the sunlight helps your body make vitamin D.

Talk with your doctor or dietitian about whether you are getting the nutrients you need. For safety reasons, also talk with your doctor before using dietary supplements or any other complementary or alternative medicines or practices. Also talk with your doctor about sun exposure and sun safety.

Lactose is in all milk and milk products and may be found in other foods and drinks.

Milk and milk products may be added to boxed, canned, frozen, packaged, and prepared foods. If you have symptoms after consuming a small amount of lactose, you should be aware of the many products that may contain lactose, such as

• bread and other baked goods, such as pancakes, biscuits, cookies, and cakes
• processed foods, including breakfast cereals, instant potatoes, soups, margarine, salad dressings, and flavored chips and other snack foods
• processed meats, such as bacon, sausage, hot dogs, and lunch meats
• milk-based meal replacement liquids and powders, smoothies, and protein powders and bars
• nondairy liquid and powdered coffee creamers, and nondairy whipped toppings

You can check the ingredient list on packaged foods to see if the product contains lactose. The following words mean that the product contains lactose:

• milk
• lactose
• whey
• curds
• milk by-products
• dry milk solids
• nonfat dry milk powder

A small amount of lactose may be found in some prescription and over-the-counter medicines. Talk with your doctor about the amount of lactose in medicines you take, especially if you typically cannot tolerate even small amounts of lactose.

You may be avoiding dairy products because of lactose intolerance. Or you might have other reasons. But dairy products are a major source of calcium, vitamin D and other nutrients that are important for your body. If you’re avoiding dairy products, you need to take special care to make sure you’re getting enough of these nutrients.

Our heart, muscles and nerves need calcium to work properly. Our bones need it to grow and stay strong. The body also needs vitamin D to absorb calcium. Nutrition surveys have shown that most people in the U.S. aren’t getting the calcium they need. If you’re avoiding milk and dairy products, you may be missing out on important sources of calcium and vitamin D.

One of the major reasons people avoid dairy products is lactose intolerance. Lactose is a natural sugar found in milk and other dairy products. You become lactose intolerant if your body doesn’t have enough lactase—an enzyme produced in the small intestine that you need to digest lactose. Undigested lactose can cause stomach cramps, gas and diarrhea within 30 minutes to 2 hours after eating something with lactose.

Lactose intolerance isn’t common in young children, but many people gradually lose their ability to digest lactose after childhood. That happens more often in some ethnic groups, such as African Americans, Native Americans, Hispanics and Asians. Most people who don’t completely digest lactose have no symptoms and are entirely healthy, but some people do get those uncomfortable symptoms.

Complicating things, some people mistake the symptoms of intestinal disorders, such as irritable bowel syndrome and inflammatory bowel disease, for lactose intolerance.

NIH recently convened a “consensus development” conference to review the scientific evidence and develop objective statements about treating lactose intolerance. The panel concluded that there isn’t enough scientific evidence to answer many questions about lactose intolerance, including how many people have it, whether it causes serious health effects or how these effects should be treated. More research will be needed to answer these questions.

If you think you or your children are lactose intolerant, studies suggest you may not need to completely eliminate milk or dairy products from your diet. There are several strategies you can try to ensure you get the nutrients you need. These include spreading your dairy intake throughout the day, combining it with other foods, taking nutritional supplements and choosing reduced-lactose or non-dairy foods rich in the nutrients found in dairy products.

How much calcium and vitamin D you need depends on your age and other factors. If you’re avoiding dairy products, talk to your doctor to make sure you meet your nutrient requirements. You can also check out the Dietary Guidelines for Americans for recommendations about dietary intake, including dairy or calcium-rich foods.

Getting Enough Calcium

If you’ve been avoiding dairy foods, try the following strategies:

• Try low-fat or fat-free milk in servings of 1 cup or less.
• Have milk with other food, such as breakfast cereal.
• Try other dairy products, such as low-fat or fat-free cheeses
  or yogurt.
• Choose lactose-free milk and milk products.
• Choose other calcium-fortified foods such as orange juice, soy or rice beverages. Some non-dairy foods, such as spinach and broccoli, have calcium, too.
• Use over-the-counter pills or drops that contain lactase, which can eliminate symptoms.
• Talk to your doctor about nutritional supplements.

Lactose intolerance may affect your health if it keeps you from getting enough nutrients, such as calcium and vitamin D. Milk and milk products, which contain lactose, are some of the main sources of calcium, vitamin D, and other nutrients.

You need calcium throughout your life to grow and have healthy bones. If you don’t get enough calcium, your bones may become weak and more likely to break. This condition is called osteoporosis. If you have lactose intolerance, you can change your diet to make sure you get enough calcium while also managing your symptoms.

What is lactose intolerance?

Lactose intolerance is a common problem. It happens when your body does not have enough lactase, which is an enzyme produced in the small intestine. Lactase is necessary to digest lactose – the natural sugar found in milk and other dairy products. In the intestines, undigested lactose leads to the buildup of gas. After eating dairy products containing lactose, people with lactose intolerance start to develop stomach cramps and diarrhea.

Lactose intolerance is a common condition that is more likely to occur in adulthood, with a higher incidence in older adults. Some ethnic and racial populations are more affected than others, including African Americans, Hispanic Americans, American Indians, and Asian Americans. The condition is least common among Americans of northern European descent.

What is osteoporosis?

Osteoporosis is a condition in which bones become less dense and more likely to fracture. Fractures from osteoporosis can result in pain and disability. In the United States, more than 53 million people either already have osteoporosis or are at high risk due to low bone mass.

Risk factors for developing osteoporosis include:

• Thinness or small frame.
• Family history of the disease.
• Being postmenopausal and particularly having had early menopause.
• Abnormal absence of menstrual periods (amenorrhea)prolonged use of certain medications, such as those used to treat lupus, asthma, thyroid deficiencies, and seizures.
• Low calcium intake.
• Lack of physical activity.
• Smoking.
• Excessive alcohol intake.

Osteoporosis often can be prevented. It is known as a silent disease because if undetected, bone loss can progress for many years without symptoms until a fracture occurs. Osteoporosis has been called a childhood disease with old age consequences because building healthy bones in youth helps prevent osteoporosis and fractures later in life. However, it is never too late to adopt new habits for healthy bones.

The link between lactose intolerance and osteoporosis

One of the primary risk factors for developing osteoporosis is not getting enough calcium in your diet. Because dairy products are a major source of calcium, you might assume that people with lactose intolerance who avoid dairy products could be at increased risk for osteoporosis. However, research exploring the role of lactose intolerance in calcium intake and bone health has produced conflicting results. Some studies have found that people with lactose intolerance are at higher risk for low bone density, but other studies have not. Regardless, people with lactose intolerance should follow the same basic strategies to build and maintain healthy bones and should pay extra attention to getting enough calcium.

Bone health strategies

Calcium and vitamin D. A well-balanced diet rich in calcium and vitamin D is important for healthy bones. Besides low-fat dairy products, good sources of calcium include dark green, leafy vegetables and calcium-fortified foods and beverages. Many low-fat and low-sugar sources of calcium are available. Also, supplements can help people with lactose intolerance meet their daily requirements of calcium and other important nutrients. The Institute of Medicine recommends a daily calcium intake of 1,000 mg (milligrams) for men and women up to age 50, increasing to 1,200 mg for women over age 50 and men over age 70.

Studies have shown that people who have at least some intestinal lactase can increase their tolerance to lactose by gradually introducing dairy products into the diet. These people can often eat small portions of dairy products without developing symptoms. The key for them is to consume small amounts of dairy products at a time so that there is enough lactase available in the intestine to digest the lactose. When the lactose is fully digested, symptoms do not develop.

Also, certain sources of dairy products may be easier for people with lactose intolerance to digest. For example, ripened cheese may contain up to 95 percent less lactose than whole milk. Yogurt containing active cultures also lessens gastrointestinal symptoms. A variety of lactose-reduced dairy products, including milk, cottage cheese, and processed cheese slices, are also available. Lactose replacement pills and liquid are also available to help with the digestion of dairy products.

Vitamin D plays an important role in calcium absorption and bone health. Food sources of vitamin D include egg yolks, fish oil, saltwater fish, liver, fortified margarine, and breakfast cereals. Many people may need vitamin D supplements to achieve the recommended intake of 600 IU (international units) each day. Men and women over age 70 should increase their uptake to 800 IU daily.

Exercise. Like muscle, bone is living tissue that responds to exercise by becoming stronger. The best activities for your bones are weight-bearing and resistance exercises. Weight-bearing exercises force you to work against gravity. They include walking, climbing stairs, and dancing. Resistance exercises – such as lifting weights – can also strengthen bones.

Healthy lifestyle. Smoking is bad for bones as well as the heart and lungs. Women who smoke tend to go through menopause earlier, which triggers earlier bone loss. In addition, people who smoke may absorb less calcium from their diets. Alcohol also can have a negative effect on bone health. Those who drink heavily are more prone to bone loss and fracture because of both poor nutrition and increased risk of falling.

Bone density testing. A bone mineral density (BMD) test measures bone density in various parts of the body. This safe and painless test can detect osteoporosis before a bone fracture occurs and can predict a person’s chances of fracturing in the future. People with lactose intolerance should talk to their doctors about whether they might be candidates for a BMD test, which can help determine whether increased attention to bone health is warranted.

Medication. Like lactose intolerance, osteoporosis has no cure. However, several medications are available for the prevention and/or treatment of the disease, including: bisphosphonates; caclcitonin; estrogen (hormone therapy); estrogen agonists/antagonists (also called selective estrogen receptor modulators or SERMs); parathyroid hormone (PTH) analog; parathyroid hormone-related protein (PTHrp) analog; RANK ligand (RANKL) inhibitor, and tissue-selective estrogen complex (TSEC).