Lactose Intolerance Symptoms, Causes, Diagnosis, Treatment, Nutritions, Diet

Lactose Intolerance Symptoms, Causes, Diagnosis, Treatment, Nutritions, Diet


What Is Lactose Intolerance?


Lactose Intolerance Symptoms, Causes, Diagnosis, Treatment, Nutritions, Diet
Lactose Intolerance

Lactose intolerance 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, may be very distressing. While not all persons deficient in lactase have symptoms, those who do are considered to be lactose intolerant.

Lactose Intolerance Symptoms & Causes


Common lactose intolerance symptoms include nausea, cramps, bloating, gas, and diarrhea, which begin about 30 minutes to 2 hours after eating or drinking foods containing lactose. The severity of lactose intolerance 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 causing lactose intolerance in babies. For most people, though, lactase deficiency is a condition that develops naturally over time. After about the age of 2 years, the body begins to produce less lactase. However, many people may not experience lactose intolerance symptoms until they are much older.

Between 30 and 50 million Americans are lactose intolerant. Certain ethnic and racial populations are more widely affected than others. As many as 75 percent of all African Americans and American Indians 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.

The lactose tolerance test begins with the individual fasting (not eating) before the test and then drinking a liquid that contains lactose. Several blood samples are taken over a 2-hour period to measure the person's blood glucose (blood sugar) level, which indicates how well the body is able to digest lactose.

Normally, when lactose reaches the digestive system, the lactase enzyme breaks down lactose into glucose and galactose. The liver then changes the galactose into glucose, which enters the bloodstream and raises the person's blood glucose level. If lactose is incompletely broken down, the blood glucose level does not rise and a diagnosis of lactose intolerance is confirmed.

Lactose Intolerance Symptoms, Causes, Diagnosis, Treatment, Nutritions, Diet
Lactose Intolerance

The hydrogen breath test measures the amount of hydrogen in the breath. Normally, very little hydrogen is detectable in the breath. However, undigested lactose in the colon is fermented by bacteria, and various gases, including hydrogen, are produced. The hydrogen is absorbed from the intestines, carried through the bloodstream to the lungs, and exhaled. In the test, the patient drinks a lactose-loaded beverage, and the breath is analyzed at regular intervals. Raised levels of hydrogen in the breath indicate improper digestion of lactose. Certain foods, medications, and cigarettes can affect the test's accuracy and should be avoided before taking the test. This test is available for children and adults.

The lactose tolerance and hydrogen breath tests are not given to check for lactose intolerance in babies and very young children who are suspected of having the condition. A large lactose load may be dangerous for very young individuals because they are more prone to dehydration that can result from diarrhea caused by the lactose. If a baby or young child is experiencing symptoms of lactose intolerance, many pediatricians simply recommend changing from cow's milk to soy formula and waiting for lactose intolerance symptoms to abate.

If necessary, a stool acidity test, which measures the amount of acid in the stool, may be given to check for lactose intolerance in babies and young children. Undigested lactose fermented by bacteria in the colon creates lactic acid and other short-chain fatty acids that can be detected in a stool sample. In addition, glucose may be present in the sample as a result of unabsorbed lactose in the colon.

Lactose Intolerance Treatment


Fortunately, lactose intolerance is relatively easy to treat. No treatment exists to improve the body's ability to produce lactase, but lactose intolerance 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 individuals differ in the amounts and types of foods they can handle. For example, one person may suffer symptoms of lactose intolerance after drinking a small glass of milk, while another can drink one glass but not two. Others may be able to manage ice cream and aged cheeses, such as cheddar and Swiss, but not other dairy products. Dietary control of lactose intolerance depends on each person's learning through trial and error how much lactose he or she can handle.

For those who react to very small amounts of lactose or have trouble limiting their intake of foods that contain lactose, lactase enzymes are available without a prescription. Lactase enzyme tablets are available 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, or longer if it is super-pasteurized.

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 may 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.

In 1997, the Institute of Medicine released a report recommending new requirements for daily calcium intake. How much calcium a person needs to maintain good health varies by age group. Recommendations from the report are as follows: 

Age group                             Amount of calcium to consume daily, in milligrams (mg)
0-6 months                                                 210 mg
6-12 months                                                 270 mg
1-3 years                                                         500 mg
4-8 years                                                         800 mg
9-18 years                                                 1,300 mg
19-50 years                                                 1,000 mg
51-70+ years                                                 1,200 mg


Also, pregnant and nursing women under 19 need 1,300 mg daily, while pregnant and nursing women over 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 following chart lists some common foods that are good sources of dietary calcium and shows about how much lactose the foods contain.

Recent research shows that yogurt with active cultures may be 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 in making yogurt produce some of the lactase enzyme required for proper digestion.

Calcium and Lactose in Common Foods


                                                                 Calcium Content                            Lactose Content
Calcium-fortified orange juice,
1 cup                                                           308-344 mg                                                0
Sardines, with edible bones,
3 oz.                                                                    270 mg                                                        0
Soymilk, fortified, 1 cup                                    200 mg                                                        0
Salmon, canned, with edible bones, 3 oz.            205 mg                                                        0
Broccoli (raw), 1 cup                                    90 mg                                                        0
Pinto beans, 1/2 cup                                            40 mg                                                        0
Orange, 1 medium                                            50 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



Clearly, many foods can provide the calcium and other nutrients the body needs, even when intake of milk and dairy products is limited. However, factors other than calcium and lactose content should be kept in mind when planning a diet. Some vegetables that are high in calcium (Swiss chard, spinach, and rhubarb, for instance) are not listed in the chart because the body cannot use their calcium content. They contain substances called oxalates, which stop calcium absorption. 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, and with enough exposure to the sun, food sources may not be necessary.

Some people with lactose intolerance may think they are not getting enough calcium and vitamin D in their diet. Consultation with a doctor or dietitian may be helpful in deciding 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? What are the sources of lactose in the diet?


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 may contain lactose, even in small amounts. Food products that may contain lactose include:

Lactose Intolerance Symptoms, Causes, Diagnosis, Treatment, Nutritions, Diet
Lactose Intolerance


  • 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

Some products labeled nondairy, such as powdered coffee creamer and whipped toppings, may also include ingredients that are derived from milk and therefore contain lactose.
Smart shoppers 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 6 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.

Elimination diet


Probably the most common way that people self-diagnose lactose intolerance is by an elimination diet, a diet that eliminates milk and milk products. There are several problems with this type of "testing."

Milk products are so common in prepared foods from the supermarket or restaurant that it is likely that an elimination diet that is not rigorous (i.e., does not eliminate all milk-containing products) will still include substantial amounts of milk. Thus, persons with severe lactase deficiency attempting an elimination diet may be ingesting enough lactose to have symptoms and erroneously conclude that lactose intolerance is not responsible for the symptoms.

People often make the assumption that they are lactose intolerant based on a short trial of elimination. A short trial may be adequate if symptoms are severe and occurring daily, but not if the symptoms are subtle and/or variable. In the latter case, an elimination diet may need to be continued for several weeks.

Because symptoms of lactose intolerance are subjective and variable, there always is the possibility of a "placebo effect" in which people think they feel better eliminating milk when, in fact, they are no better. As discussed previously, with subjective symptoms such as those of lactose intolerance, a placebo effect might be expected to occur 20%-40% of the time.

If an elimination diet is to be used for diagnosing lactose intolerance, it should be a rigorous diet. A rigorous diet requires counseling by a dietician or reading a guide to a lactose-elimination diet. The diet also needs to be continued long enough to clearly evaluate whether or not symptoms are better. If there is doubt about improvement on the diet, particularly if symptoms normally fluctuate in intensity over weeks or months, repeated periods of lactose elimination should be tried until a firm conclusion can be drawn. Elimination of all milk products should eliminate symptoms completely if lactose intolerance alone is the cause of the symptoms.

What to do about your child’s lactose intolerance


The treatment for lactose intolerance can depend on the cause. If your child has primary lactose intolerance, your doctor, paediatrician or nutritionist will help guide you.

For secondary lactose intolerance caused by gastroenteritis:


  • try using Lactaid drops that contain the enzyme lactase – but note there’s some debate about the effectiveness of this treatment
  • alternate your baby’s breastfeeds with a lactose-free infant formula. If the situation is particularly serious, you might have to wean your baby onto the formula for a while. If this happens, you can express breastmilk to keep up your supply.

If you’re breastfeeding, persist if possible. Because of the nutritional value of breastmilk, and the benefits of lactose for your baby’s growth, weaning isn’t recommended. And if your child can tolerate a small amount of lactose, gradually increasing it can help her body produce more lactase.

One of the most important things you can do is soothe and comfort your baby when he’s showing symptoms.

Talk to your doctor if you’re thinking of replacing or alternating breastmilk with a soy-based or other lactose-free formula. You can also talk to a community nurse or lactation consultant if you’re concerned about alternating breastfeeding and bottle-feeding.

Food allergy versus lactose intolerance


Sometimes symptoms we think indicate lactose intolerance are actually caused by a food allergy. An allergy to milk, for example, affects bottle-fed babies more than breastfed babies because the majority of infant formulas are based on cow’s, goat’s or soy milk.

It’s very rare for babies to be allergic to human breastmilk. But an allergy might develop from proteins eaten by a breastfeeding mother, which are then transferred to her baby via her breastmilk. An elimination diet can be used to diagnose such an allergy. This involves removing dairy foods such as milk, cheese, yogurt and cream from the mother’s diet. If the baby’s symptoms improve but then return when mum reintroduces the foods, this might suggest an allergy.

Reactions to food allergies are more severe than allergies to lactose intolerance. If your baby’s allergic to food such as cow’s milk, soy products or egg, you might notice the following symptoms:


  • vomiting
  • blood or mucus in his diarrhea
  • poor weight gain
  • wheezing or asthma.