Lactose Intolerance

What Is It?

Lactose intolerance is a common cause of abdominal cramping, bloating and diarrhea. This condition occurs when the body does not have enough of the intestinal enzyme lactase, which breaks down lactose, the main sugar in milk, into simpler forms that can then be absorbed into the bloodstream. When lactose can't be digested in the small intestine, it passes quickly into the colon. Bacteria in the colon break down some of the lactose, producing hydrogen gas. The remaining lactose also draws water into the colon, causing diarrhea, bloating and flatulence (gas).

Lactose intolerance usually is genetic (inherited). In many people of African or Asian descent, the body begins making less lactase around age 5. As many as 90% of Asian-Americans, 80 percent of American Indians, 65% of African-Americans and 50% of Hispanics have some degree of lactose intolerance. In contrast, most Caucasians (80%) have a gene that preserves the ability to produce lactase into adulthood. Another cause of lactose intolerance is a rare syndrome called congenital lactase deficiency. Infants with this condition do not produce any lactase. Unable to digest lactose, the infants have diarrhea from birth. This condition usually was fatal before the development of lactose-free infant formulas.

Difficulty digesting lactose, also can be caused by several gastrointestinal disorders. Viral or bacterial gastroenteritis and other diseases, such as celiac sprue, can destroy the lactase-producing cells that line the small bowel. A condition called bacterial overgrowth, in which the small bowel contains more bacteria than normal, can cause lactose intolerance. The bacteria break down lactose in the small bowel, causing flatulence and diarrhea.

Symptoms

Common symptoms of lactose intolerance include:

• Watery, bulky, odd-smelling stools
• Nausea
• Abdominal pain
• Cramps
• Bloating
• Flatulence that begins about 30 minutes to two hours after eating or drinking foods or drinks containing lactose.

The severity of symptoms varies, depending on the amount of lactose an individual can tolerate, the amount of lactose ingested, and the size and fat content of the meal. People who also have irritable bowel syndrome tend to have more severe symptoms from lactose intolerance.

Diagnosis

It's possible you have lactose intolerance if your symptoms improve dramatically when you avoid lactose. In some cases, your doctor will want to do tests to confirm the diagnosis.

The most commonly used test to confirm the diagnosis is the lactose breath hydrogen test. The test is painless and noninvasive. You cannot eat food for several hours beforehand.

You begin the test by drinking a liquid that contains lactose. Your breath is then sampled for hydrogen over a few hours. Normally, very little hydrogen is detected in your breath. However, if you have lactose intolerance, the bacteria in your intestine will break the undigested lactose into hydrogen, which then moves through the bloodstream to your lungs and exhaled. You will be diagnosed with lactose tolerance if higher-than-normal hydrogen levels are detected during this test.

An alternative test is the lactose tolerance test. You take the test on an empty stomach, and you begin by drinking a lactose solution. This test measures blood sugar levels at selected intervals over a few hours to determine your ability to digest lactose. If the lactose is digested, it produces glucose, which elevates your blood sugar level. You will be diagnosed with lactose intolerance if your blood sugar levels fo not change during this test.

A significant number of people who have symptoms that suggest lactose intolerance will have normal results on diagnostic tests. Other possible causes of symptoms similar to lactose intolerance include intolerance to another substance in dairy products, poor digestion of other sugars or complex carbohydrates (which can be determined with a careful dietary history), and irritable bowel syndrome.

Expected Duration

People who develop lactose intolerance as a result of another gastrointestinal disease can recover completely when the intestinal problem is treated, but this may take several weeks to months.

When lactose intolerance is genetic, the condition is permanent. However, people can avoid symptoms by avoiding foods that contain lactose or by eating them in moderation. In addition, enzyme formulations are available, although these products usually do not relieve the symptoms entirely.

Prevention

There is no way to prevent lactose intolerance.

Treatment

There are two main ways to treat lactose intolerance:

• Monitoring the amounts of lactose in foods
• Taking commercially available enzyme substitutes

People with lactose intolerance need to read labels of all prepared foods to se if they contain lactose. The highest concentrations are found in ice cream and milk. Cheeses typically have lower amounts of lactose. Some products listed as nondairy, such as powdered coffee creamer and whipped toppings, may contain lactose if they contain ingredients that are derived from milk. When you read food labels, look for words such as whey, curds, milk byproducts, dry milk solids and nonfat dry milk powder. If any of these ingredients are on the label, the product probably contains lactose.

If you completely avoid lactose, your symptoms should go away. If they do not, the diagnosis might not be correct. Many people will be able to tolerate a gradual increase in lactose intake if they are careful to monitor their symptoms. Doctors often recommend ice cream for this. It tends to be tolerated better than other foods that contain lactose because of its high fat content. As you gradually increase your lactose levels, review your diet with your doctor or a nutritionist to be sure that you are eating the proper proportions of fat, protein and other nutrients.

There are several commercially available enzyme formulations (tablets and liquids) that can serve as lactase replacements. You can add these to foods that contain lactose to reduce symptoms significantly. However, these products rarely get rid of symptoms completely, and the results vary among people and with different product formulations. Pretreated dairy products are an extremely effective alternative. You can add enzyme drops to milk and then refrigerate the milk for 24 hours before use or you can purchase dairy products that have been treated to reduce the lactose. Note that acidophilus milk still has too much lactose depleted to be useful for most people with lactose intolerance.

Many people with lactose intolerance have a difficult time getting enough calcium in their diet. This increases the risk of osteoporosis, a condition in which bones become thin and fragile. Studies have shown that people who are lactose intolerant have double the risk of fractures. Therefore, it is essential that you consume at least 1,000 milligrams of calcium each day (1,200 milligrams if you are a postmenopausal woman). Most people with lactose intolerance are able to tolerate live culture yogurt as long as it does not contain milk products. Vegetables such as broccoli, Chinese cabbage, collard greens and kale are excellent sources of calcium. If you are not able to get enough calcium in your diet, take a daily calcium supplement.

When To Call A Professional

Call your doctor if you develop symptoms of lactose intolerance after eating dairy products. Although this condition is not dangerous, it can be distressing. There are effective treatments available, so there is no need to suffer.

Prognosis

The outlook for people with lactose intolerance is excellent. Symptoms can be alleviated if dairy products are limited or avoided, or taken in combination with a commercially available enzyme formulation.

Additional Info

National Institute of Diabetes & Digestive & Kidney Disorders

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Bethesda, MD 20892-2560

Phone: (301) 496-4000

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http://www.niddk.nih.gov/