What Is Lactose Intolerance?
Lactose intolerance – a condition that affects 30 and 50 million Americans – is the inability to digest significant amounts of lactose, the predominant sugar of milk. This inability results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down milk sugar into simpler forms that can then be absorbed into the bloodstream. When there is not enough lactase to digest the amount of lactose consumed, the results, although not usually dangerous, can be very distressing.
Common symptoms include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to two hours after eating or drinking foods containing lactose. The severity of symptoms varies depending on the amount of lactose each individual can tolerate.
Some causes of lactose intolerance are well known. For instance, certain digestive diseases and injuries to the small intestine can reduce the amount of enzymes produced. In rare cases, children are born without the ability to produce lactase. For most people, though, lactase deficiency is a condition that develops naturally over time. After the age of two, the body naturally begins to produce less lactase. However, many people don't experience symptoms until they are much older.
Certain ethnic and racial populations are more widely affected than others. As many as 75 percent of all African Americans and Native Americans and 90 percent of Asian Americans are lactose intolerant. The condition is least common among persons of northern European descent.
How Is Lactose Intolerance Diagnosed?
The most common tests used to measure the absorption of lactose in the digestive system are the lactose tolerance test, the hydrogen breath test, and the stool acidity test. These tests are performed on an outpatient basis at a hospital, clinic, or doctor's office.
Researchers have identified a genetic variation associated with lactose intolerance, which might be useful in developing a test to identify people with this condition.
How Is Lactose Intolerance Treated?
Fortunately, lactose intolerance is relatively easy to treat. No treatment can improve the body's ability to produce lactase, but symptoms can be controlled through diet.
Young children with lactase deficiency should not eat any foods containing lactose. Most older children and adults need not avoid lactose completely, but people differ in the amounts and types of foods they can handle. For example, one person might have symptoms after drinking a small glass of milk, while another can drink one glass but not two. Others might be able to eat ice cream and aged cheeses, such as cheddar and Swiss, but not other dairy products. Dietary control of lactose intolerance depends on people learning through trial and error how much lactose they can handle.
For those who react to very small amounts of lactose or have trouble limiting their intake of foods that contain it, lactase enzymes are available without a prescription to help people digest foods that contain lactose. The tablets are taken with the first bite of dairy food. Lactase enzyme is also available as a liquid. Adding a few drops of the enzyme will convert the lactose in milk or cream, making it more digestible for people with lactose intolerance.
Lactose-reduced milk and other products are available at most supermarkets. The milk contains all of the nutrients found in regular milk and remains fresh for about the same length of time.
How Is Nutrition Balanced?
Milk and other dairy products are a major source of nutrients in the American diet. The most important of these nutrients is calcium. Calcium is essential for the growth and repair of bones throughout life. In the middle and later years, a shortage of calcium can lead to thin, fragile bones that break easily, a condition called osteoporosis. A concern, then, for both children and adults with lactose intolerance, is getting enough calcium in a diet that includes little or no milk.
The following table, from the Institute of Medicine, shows – by age group – how much calcium a person needs in order to maintain good health.
| Age Group |
Calcium Needed Daily (mg) |
| 0-6 months |
200 mg |
| 7-12 months |
260 mg |
| 1-3 years |
700 mg |
| 4-8 years |
1,000 mg |
| 9-18 years |
1,300 mg |
| 19-50 years |
1,000 mg |
| 51-70+ years |
1,200 mg |
Pregnant and nursing women under age 19 need 1,300 mg daily, while pregnant and nursing women over age 19 need 1,000 mg.
In planning meals, making sure that each day's diet includes enough calcium is important, even if the diet does not contain dairy products. Many nondairy foods are high in calcium. Green vegetables, such as broccoli and kale, and fish with soft, edible bones, such as salmon and sardines, are excellent sources of calcium. To help in planning a high-calcium and low-lactose diet, the table that follows lists some common foods that are good sources of dietary calcium and shows how much lactose they contain.
Recent research shows that yogurt with active cultures is a good source of calcium for many people with lactose intolerance, even though it is fairly high in lactose. Evidence shows that the bacterial cultures used to make yogurt produce some of the lactase enzyme required for proper digestion.
| Calcium and Lactose in Common Foods |
|
|
| Vegetables |
Calcium Content |
Lactose Content |
| Calcium-fortified orange juice, 1 cup |
308-344 mg |
0 |
| Sardines, with edible bones, 3 oz |
270 mg |
0 |
| Salmon, canned, with edible bones, 3 oz |
205 mg |
0 |
| Soymilk, fortified, 1 cup |
200 mg |
0 |
| Broccoli (raw), 1 cup |
90 mg |
0 |
| Orange, 1 medium |
50 mg |
0 |
| Pinto beans, 1/2 cup |
40 mg |
0 |
| Tuna, canned, 3 oz |
10 mg |
0 |
| Lettuce greens, 1/2 cup |
10 mg |
0 |
| |
|
|
| Dairy Products |
|
|
| Yogurt, plain, low-fat, 1 cup |
415 mg |
5 g. |
| Milk, reduced fat, 1 cup |
295 mg |
11 g |
| Swiss cheese, 1 oz |
270 mg |
1 g |
| Ice cream, 1/2 cup |
85 mg |
6 g |
| Cottage cheese, 1/2 cup |
75 mg |
2-3 g |
Adapted from Manual of Clinical Dietetics. 6th ed. American Dietetic Association; and Soy Dairy Alternatives.
Calcium is absorbed and used only when there is enough vitamin D in the body. A balanced diet should provide an adequate supply of vitamin D. Sources of vitamin D include eggs and liver. However, sunlight helps the body naturally absorb or synthesize vitamin D.
Some people with lactose intolerance might not be getting enough calcium and vitamin D in their diet. Consulting with a doctor or dietitian could help you decide whether any dietary supplements are needed. Taking vitamins or minerals of the wrong kind or in the wrong amounts can be harmful. A dietitian can help in planning meals that will provide the most nutrients with the least chance of causing discomfort.
What Is Hidden Lactose?
Although milk and foods made from milk are the only natural sources, lactose is often added to prepared foods. People with very low tolerance for lactose should know about the many food products that might contain even small amounts of lactose, such as:
- 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 products labeled "non-dairy," such as powdered coffee creamer and whipped toppings, might still include ingredients derived from milk and that contain lactose.
Learn to read food labels with care, looking not only for milk and lactose among the contents, but also for such words as whey, curds, milk by-products, dry milk solids, and nonfat dry milk powder. If any of these are listed on a label, the product contains lactose.
In addition, lactose is used as the base for more than 20 percent of prescription drugs and about six percent of over-the-counter medicines. Many types of birth control pills, for example, contain lactose, as do some tablets for stomach acid and gas. However, these products typically affect only people with severe lactose intolerance.
Summary
Even though lactose intolerance is widespread, it need not pose a serious threat to good health. People who have trouble digesting lactose can learn which dairy products and other foods they can eat without discomfort and which ones they should avoid. Many will be able to enjoy milk, ice cream, and other such products if they take them in small amounts or eat other food at the same time. Others can use lactase liquid or tablets to help digest the lactose. Even older women at risk for osteoporosis, and growing children who must avoid milk and foods made with milk can meet most of their special dietary needs by eating greens, fish, and other calcium-rich foods that are free of lactose. A carefully chosen diet, with calcium supplements (if the doctor or dietitian recommends them), is the key to reducing symptoms and protecting your health.
For More Information
Go to: American Dietetic Association (ADA) and International Foundation for Functional Gastrointestinal Disorders (IFFGD) Inc.
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