Lactose Intolerance
Volume 5, Number 7 - September, 2001
Editors: Carol A. Rice, Ph.D., RN, Professor and Extension Health Specialist, and Janet M. Pollard, MPH, Extension Associate-Health
Inside HealthHints....
- Lactose Intolerance
- Physiology: What Happens in the Body
- World Issues Concerning Lactose Intolerance
- Symptoms
- Diagnosing Lactose Intolerance
- Lactose Maldigestion vs. Lactose Intolerance
- Importance of Dairy Products
- Getting Enough Calcium and Other Nutrients
- Tips for Managing Lactose Intolerance
- Hidden Lactose: The Importance of Reading Labels
- An Important Distinction: Allergy vs. Intolerance
- Designing Your Personal Plan
- Websites with Reliable Information
- Tips for Managing Lactose Intolerance (handout) [pdf version]
- References
Lactose Intolerance
When ingestion of a particular food causes unpleasant symptoms, a person is said to be intolerant of that food (Dandalides, 2001). By far the most common food intolerance is lactose intolerance (Dandalides, 2001). Lactose intolerance is a set of symptoms resulting from the body's inability to digest significant amounts of lactose, the predominant sugar of milk (American Dietetic Association, 1996; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
Though lactose intolerance is not a serious or life threatening condition, it is common, and can be extremely unpleasant if not diagnosed and managed well.
If you are experiencing symptoms of lactose intolerance, you are not alone:
- Close to 50 million Americans (25% of the U.S. population) suffer from lactose intolerance.
- An estimated 90% of Asian-Americans are lactose intolerant.
- An estimated 75% of all African-American, Jewish, Native American, and Mexican-American adults are lactose intolerant.
- About 15% of Caucasians are lactose intolerant (American Dietetic Association, 1996; American Gastroenterological Association; 2001; National Dairy Council, 2001a).
Physiology: What Happens in the Body
The inability to digest lactose results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. The job of the lactase enzyme is to break lactose down into a simpler form (simple sugars) that can then be absorbed into the bloodstream and travel to the body's cells where it provides the body's energy, helps form proteins, or is stored for future use (Dandalides, 2001; American Dietetic Association, 1996; International Food Information Council Foundation, 1999; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
When there is not enough lactase enzyme to digest the amount of lactose consumed, negative symptoms result.
World Issues Concerning Lactose Intolerance
The abundance of diets around the world that are low in dairy products means lactose intolerance is widespread (Skolnik, 2000).
"Minorities lack the ability to digest lactose because they come from areas of the world where they didn't have lots of dairy products in their diets for generations, so over time their lactase enzymes (the enzymes that deal with lactose in the body) became deactivated (Natalie Webb, American Academy of Allergy, Asthma, and Immunology)" (Skolnik, 2000).
Symptoms
Symptoms of lactose intolerance result when the activity of the lactase enzyme is low. If not digested in the small intestine, undigested lactose may enter the large intestine where naturally residing, gas-producing bacteria ferment it. This fermentation can lead to symptoms of lactose intolerance (National Dairy Council, 2001a). Symptoms commonly include:
- nausea
- abdominal pain/cramps
- bloating
- gas/flatulence
- diarrhea (National Dairy Council, 2001a; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
Symptoms typically begin 30 minutes to 2 hours after eating or drinking foods containing lactose (National Institute of Diabetes and Digestive and Kidney Diseases, 1998a). The severity of symptoms, however, varies because different individuals can tolerate different amounts of lactose, based on the amount of lactase enzyme they have available in their digestive system. Other, less common symptoms resulting from lactose intolerance may include:
- abdominal distention
- stools floating (a sign of an absorption problem)
- foul smelling stools
- weight loss or malnutrition (often due to eliminating nutrient-rich dairy products) (Owens, 2001).
Diagnosing Lactose Intolerance
There are typically four ways in which lactose intolerance might be diagnosed:
- avoidance/re-challenge
- lactose tolerance test
- hydrogen breath test
- stool acidity test.
Avoidance/Re-challenge
Though there are three formal tests that can be done to try to diagnose lactose intolerance, most cases can be diagnosed by completely avoiding lactose-containing products for several weeks to see if symptoms diminish or are alleviated completely. The person's digestive system is then re-challenged with lactose-containing foods. If the symptoms return after re-challenging the digestive system with lactose-containing foods after noticing a dramatic reduction in symptoms with avoidance, the diagnosis of lactose intolerance is likely (Dandalides, 2001).
Lactose Tolerance Test
Prior to the lactose tolerance test, the individual must fast (not eat). The test is performed by drinking a liquid that contains the sugar called lactose. Blood samples are taken over a 2-hour period to measure the blood glucose (sugar) level, indicating how well the body is able to digest the lactose (American Gastroenterological Association, 2001).
Normally, when lactose reaches the small intestine it is broken down into the simple sugars glucose and galactose, which are then absorbed into the blood -- this raises a person's blood glucose level. If the lactose is not completely broken down, the blood glucose does not rise, indicating lactose intolerance (American Gastroenterological Association, 2001; MedicineNet, 2001).
Hydrogen Breath Test
Prior to the hydrogen breath test, the individual must fast for 12 hours. In this test, the individual drinks a lactose loaded beverage and then blows into and fills a balloon with a breath of air. The concentration of hydrogen is measured in a sample from the balloon at different intervals (MedicineNet, 1999a; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
Normally, there is little or no hydrogen detected in the breath; however, undigested lactose in the colon is fermented by bacteria, which produces various gases, including hydrogen. Raised levels of hydrogen indicate lactose is not being digested properly.
Note: Neither the lactose tolerance test, nor the hydrogen breath test are administered to very young children suspected of having lactose intolerance. Symptoms resulting from a large lactose load could be dangerous to young children. Young children are more susceptible to dehydration resulting from diarrhea.
Stool Acidity Test
In this test a very small dose of lactose is ingested, and a stool sample taken. In addition to hydrogen, 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. Glucose may also be present in the sample as a result of unabsorbed lactose in the colon.
The stool acidity test is most often used for infants and young children because it does not pose any risk due to the small amounts of lactose ingested (American Gastroenterological Association, 2001; MedicineNet, 1999b; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
Because an accurate diagnosis is important to your current and future health, it is important not to self-diagnose lactose intolerance. If you are experiencing symptoms, see your doctor. Though some of these symptoms can be unpleasant to talk about, your doctor will understand. Try to speak openly and be straight forward about your symptoms so your doctor can get to the heart of the problem and you can begin feeling better as soon as possible.
Accurate diagnosis of food intolerance is important to avoid unnecessary diet restrictions -- which might lead to poor nutrition, higher food costs, social inconvenience/isolation, and preventing a more serious underlying disease from being left undiagnosed (Dandalides, 2001).
Lactose Maldigestion versus Lactose Intolerance
It is important to make one note of distinction. In many population groups, lactase begins to decline after the age of 2, usually between ages 3 to 5 years. This is a normal, genetically controlled decline in lactase enzyme, known as lactose maldigestion (i.e., low levels of the intestinal enzyme lactase).
Lactase maldigestion is the not the same as lactose intolerance. Many people with lactose maldigestion do not experience the gastrointestinal symptoms following intake of lactose that those with lactose intolerance do. In order to be considered lactose intolerant, the amount of lactose consumed must exceed the amount that can be broken down by the available lactase enzymes, thus resulting in negative symptoms.
Some individuals will produce enough lactase enzyme throughout life, while others may only produce it during infancy and early childhood. Consequently, as the intestinal enzyme wanes, the individual may begin to develop symptoms of lactose intolerance (National Dairy Council, 2001a; National Dairy Council, 2001b).
Importance of Dairy Products
Milk and other dairy products, the major lactose-containing products, are also a major source of nutrients in the American diet -- most importantly, calcium. Calcium is essential for the growth and repair of bones throughout life. It is particularly important in our middle and later years because a calcium shortage can lead to fragile bones that break easily (a condition known as osteoporosis) (American Gastroenterological Association, 2001; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a). (For more information on osteoporosis, see the July/August 2000 issue of HealthHints.)
Recent studies have also shown that calcium intake can lower blood pressure and cholesterol and prevent colon cancer, especially among African American individuals (Skolnik, 2000). An adequate intake of calcium can reduce the risk of major chronic disorders such as hypertension, colon cancer, stroke, osteoporosis, and perhaps even overweight and obesity (National Dairy Council, 2001a).
In addition to calcium, dairy products provide us with other nutrients that are critical to our health, which include:
- high quality protein
- phosphorus
- potassium
- riboflavin
- vitamin B12
- vitamin A
- magnesium
- Vitamin B6
- thiamin
- Vitamin D
- niacin (Skolnik, 2000; National Dairy Council, 2001a).
Getting Enough Calcium and Other Nutrients
People intolerant of dairy products must find some way to replace the calcium and other nutrients lost by not ingesting dairy products. While many nondairy foods are high in calcium, such as many green vegetables and fish with soft, edible bones, getting enough calcium with no dairy in the diet is very difficult. Further, maintaining an adequate intake of calcium without dairy requires substantial nutritional knowledge. For example, while some vegetables are high in calcium such as Swiss chard, spinach, and rhubarb, the calcium in them cannot be utilized by the body. These products contain substances called oxalates, which stop calcium absorption (National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
Here is a sample list of alternative food sources of calcium:
- broccoli
- Chinese cabbage (bok choy)
- kale
- turnip greens
- oysters
- salmon with bones
- sardines
- shrimp
- tofu
- molasses.
It is also important to note that although these foods are somewhat calcium-rich, it is very difficult to get enough calcium through these sources. A cup of milk has 300mg of calcium and a cup of yogurt 400mg; to equal that, you would need to eat approximately 3 cups of cooked broccoli or 2 cups of cooked collard greens.
For those who are lactose intolerant, a calcium supplement may be recommended. Health experts regard calcium supplements as a supplement to, not a substitute for, a nutritionally adequate diet (National Dairy Council, 2001a). Keep in mind that a doctor is the best person to decide whether dietary supplements are needed. Taking vitamins or minerals of the wrong kind or in the wrong amounts can be harmful (American Gastroenterological Association, 2001). (For more information on calcium supplements as well as Recommended Daily Allowances of calcium, see the July/August 2000 issue of HealthHints.)
Tips for Managing Lactose Intolerance
Though there is no cure for lactose intolerance, there are many ways it can be managed. Here are a few tips that may help:
- Adjust the amount of lactose consumed. Individuals with lactose intolerance vary in the amount of lactose they can tolerate (some producing more lactase enzyme than others). Thus, to determine how much lactose is well tolerated, individuals should consume a small amount of milk (less than one cup) with food and gradually increase the serving size of milk and milk products until symptoms just begin to develop.
- Pair dairy with other foods. Don't drink milk on an empty stomach. Other foods will slow digestion and allow what lactase enzyme the individual does have to do its job.
- Select foods wisely. Some dairy foods are better tolerated than others.
- Though it is fairly high in lactose, yogurt with "live active cultures" is a good source of calcium and often well tolerated. There is recent research evidence that the bacterial cultures used in making the yogurt produce the lactase required for proper digestion (American Gastroenterological Association, 2001).
- When it comes to cheese, older is wiser. Some lactose gets removed in the cheese making process. Aged, hard cheeses like cheddar, swiss, colby, and parmesan are particularly low in lactose and generally well tolerated.
- Cultured dairy products, such as sweet acidophilus milk, yogurt milk, and other fermented dairy foods are also generally tolerated as well as milk.
- Try lactose-reduced or lactose-free products. Some examples of products made lactose-reduced or lactose-free include:
- non-fat, lowfat, and calcium fortified milk
- cottage cheese
- yogurt
- ice cream.
These products and other products containing lactose-hydrolyzed milk contain all the same nutrients, including calcium, as their regular counterparts.
- Take lactase enzyme tablets. You can purchase these tablets over-the-counter to take prior to eating or with dairy products.
- Use lactase enzyme drops. This liquid lactase enzyme can be purchased over-the-counter and added to regular milk.
- Build-up tolerance for lactose. Gradually increasing intake of lactose-containing foods may actually improve tolerance to lactose. Consuming dairy products infrequently may make your symptoms worse when you do consume lactose. It is important to incorporate dairy products into your diet slowly and in small amounts (e.g. 1/2 glass of milk at a time) to activate your lactase enzyme again and build up your tolerance to lactose. Continued exposure to lactose may actually enhance the efficiency of the bacteria in the colon to metabolize lactose, thereby minimizing symptoms (Sebella, 1996; Skolnik, 2000; American Dietetic Association, 1996; American Gastroenterological Association, 2001; National Dairy Council, 2001a).
Hidden Lactose: The Importance of Reading Labels
Another important tip for those who are lactose intolerant is to watch out for hidden lactose. Lactose is hidden in some foods. For instance, some products are labeled non-dairy, but include ingredients derived from milk, such as powdered coffee creamer or whipped topping. Likewise, though milk and foods made from milk are the only natural sources of lactose, it is often added to prepared foods. Some common food products that may contain lactose include:
- 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.
Though some people who are lactose intolerant may not be bothered by the lactose in these prepared foods, those who have a lower tolerance for lactose will need to read these labels carefully.
A helpful hint in reading food labels is to look for the following words in the ingredient list:
- lactose
- milk
- whey
- curds
- milk by-products
- milk solids, dry milk solids, or dried milk
- nonfat dry milk powder or powdered milk
- butter
- cheese
- cream.
If any of these terms is listed on the label, the item contains lactose (American Gastroenterological Association, 2001; Dandalides, 2001; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a; National Institute of Diabetes and Digestive and Kidney Diseases, 1998b).
In addition to reading food labels, the person with lactose intolerance should also read drug labels or consult with their doctor or pharmacist when taking medications. Lactose is used as a base in over 20% of prescription drugs and about 6% of over-the-counter medications. Many types of birth control pills, for example, contain lactose, as do some tablets for stomach acid and gas -- an important piece of information for those trying to treat symptoms related to lactose intolerance.
As with prepared foods, for most individuals, the lactose in medications may have no effect; however, those who have a lower tolerance for lactose will need to read these labels carefully (Dandalides, 2001; National Institute of Diabetes and Digestive and Kidney Diseases, 1998a).
An Important Distinction: Allergy versus Intolerance
Does milk give you a stomach ache? If so, consider yourself among the millions of Americans who believe they have a food allergy. Surprisingly, though, relatively few of us are truly allergic to milk. Most of the time, the problem is a milk or lactose intolerance. The difference may sound like a little more than a play on words, but for the unlucky few, the distinction is a matter of life and death (Goldstein, 1998).
A true milk allergy occurs when an individual's immune system overreacts to milk, resulting in the production of the IgE (Immunoglobin E) antibody, that specifically binds to the milk protein.
Lactose intolerance, on the other hand, is a physical response to milk or lactose. It differs from an allergy in that it does not involve the immune system (American Academy of Allergy, Asthma, and Immunology, 1996; Goldstein, 1998).
While the person with lactose intolerance may experience a bloated feeling or gas after consuming milk or dairy products, consumption of milk or dairy products by a person with milk allergy may have life threatening consequences. Individuals who have a true milk allergy must avoid all milk proteins (International Food Information Council Foundation, 1997).
Common symptoms of milk allergy include skin irritations (rashes, hives, eczema), gastrointestinal symptoms (nausea, diarrhea, vomiting), sneezing, runny nose, shortness of breath, and sometimes anaphylaxis -- a severe reaction that may include hives, swelling of the throat, difficulty breathing, lower blood pressure, and unconsciousness (International Food Information Council Foundation, 1998).
Thus, while lactose intolerance is the lack of an enzyme that can be added into the diet to allow individuals to safely enjoy milk products, milk allergy is caused by an immune response and can involve multiple parts of the body -- the only way to avoid such reactions is to avoid ingesting milk products entirely (Munoz-Furlong, 1999).
Designing Your Personal Plan
Lactose intolerance is quite common and manageable. Total avoidance of lactose could produce tragic results such as osteoporosis and fractures. Once sure lactose intolerance is the problem, developing a plan to maintain an adequate intake of the nutrients once obtained in dairy products is essential.
Closely monitoring symptoms, working with a doctor or dietician, and using the tips for managing lactose intolerance included in this issue of HealthHints can make a big difference in maintaining overall health.
Websites with Reliable Information
- Lactose Intolerance (American Dietetic Association)
[http://www.eatright.org/Public/NutritionInformation/92_nfs43.cfm] - Lactose Intolerance (American Gastroenterological Association)
[http://www.gastro.org/clinicalRes/brochures/lactose.html] - Lactose Intolerance (National Institute of Diabetes and Digestive and Kidney Diseases)
[http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/] - Lactose Intolerance and Minorities: The real story (National Dairy Council)
[http://www.nationaldairycouncil.org/nutrition/lactose/lactoseIntolerance.asp] - Why Does Milk Bother Me? (National Institute of Diabetes and Digestive and Kidney Diseases)
[http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance_ez/]
References
- American Dietetic Association (1996). Lactose intolerance [on-line]. Available:
http://www.eatright.org/nfs/nfs43.html. - American Gastroenterological Association (2001). Lactose intolerance [on-line]. Available:
http://www.gastro.org/public/lactose.html. - American Academy of Allergy, Asthma, and Immunology (1996). Tips to remember: food allergy [on-line].
http://www.aaaai.org/public/publicedmat/tips/foodallergy.stm. - Dandalides, SM (2001). Common gastrointestinal problems: Food intolerance [on-line]. Available:
http://www.acg.gi.org/acg-dev/patientinfo/cgp/cgpvol3.html. - Goldstein, S. (1998). Is it milk allergy or lactose intolerance? [on-line]. Available:
http://www.aaaai.org/public/publicedmat/advocate/1998/98spring.stm. - International Food Information Council Foundation (1997). Food allergy myths and realities [on-line]. Available: http://www.ific.org/proactive/newsroom/release.vtml?
id=18587&PROACTIVE_ID= cecfcfcac7cdccc7cbc5cdc
fcfcfc5cdcfc9cbc8cfcccfc8ecfcf. - International Food Information Council Foundation (1999). Questions and answers about sugars [on-line]. Available:
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cbc8cfcccfc8cec5cf. - International Food Information Council Foundation (1998). Understanding food allergy [on-line]. Available:
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cfcfcfc5cecfc9cbc8cfcccfc8cec5cf. - MedicineNet (1999a). Hydrogen breath test [on-line]. Available:
http://www.FocusOnDigestion.com/script/main/art.asp?articlekey=8041. - MedicineNet (2001). Lactose tolerance test [on-line]. Available:
http://www.FocusOnDigestion.com/script/main/art.asp?articlekey=7543. - MedicineNet (1999b). Stool acidity test [on-line]. Available:
http://www.FocusOnDigestion.com/script/main/art.asp?li=MNI&ArticleKey=7545. - Munoz-Furlong, A. (1999). Is it milk intolerance or milk allergy? [on-line]. Available:
http://www.aaaai.org/public/publicedmat/advocate/1999/spring/milk.stm. - National Dairy Council (2001a). Lactose intolerance and minorities: The real story [on-line]. Available:
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Available: http://www.niddk.nih.gov/health/digest/pubs/lactose/lactose.htm. - National Institute of Diabetes and Digestive and Kidney Diseases (1998b). Why does milk bother me? [on-line]. Available: http://www.niddk.nih.gov/health/digest/pubs/whymilk/index.htm.
- Owen, MM (2001). Medlineplus medical encyclopedia: Lactose intolerance [on-line]. Available:
http://www.nlm.nih.gov/medlineplus/ency/article/000276.htm. - Sebella, L. (1996). Low-cal cooking -- some helpful advice for lactose intolerance [on-line]. Available:
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html/2001/02/21/prjr/0000-4853-keyword.missing.stm. - Skolnik, L. (2000). Is milk bad for some people -- or is it getting a bad rap? [on-line]. Available:
http://www.aaaai.org/news/siteware/output/html/
2000/12/01/knikn/5752-0013-kidnews-milk.tb.stm. - United States Department of Agriculture (2001). The Food Guide Pyramid: A guide to daily food choices [on-line]. Available: http://www.nalusda.gov:8001/py/pmap.htm.
