Table of Contents
Lactose intolerance is a condition caused by the inability to digest lactose, a sugar found in milk. The lactose intolerance diet is a diet designed to treat the symptoms that result from undigested lactose.
No single person originated the lactose intolerance diet. Physicians treating symptoms of lactose intolerance have developed this diet through observation and trial and error by their patients.
Lactose is the main sugar in milk. Normally when lactose reaches the small intestine, it is broken down into simpler sugars by the enzyme lactase. These simpler sugars are absorbed into the bloodstream and eventually are used as fuel for he body.
Lactase is made in the cells that line the small intestine. In some people, these cells do not make enough
(Illustration by GGS Information Services/Thomson Gale.)
lactase. In a few people, they do not make any at all. When people do not make enough lactase, they cannot digest some portion of the lactose they have eaten. Lactose that is not broken down cannot be absorbed into the blood. Instead, it remains in the large intestine (colon) where bacteria convert it into lactic acid. Lactic acid is a laxative and an irritant to the colon.
Symptoms of lactose intolerance include nausea, bloating, abdominal pain or cramps, abundant gas, and diarrhea. These symptoms usually begin anywhere from 30 minutes to 2 hours after eating a food that contains lactose. Symptoms of lactose intolerance can be uncomfortable enough to temporarily interfere with daily activities, however, they do not harm the digestive system and lactose intolerance does not progress to any other disease or disorder.
Lactose intolerance is an extremely common condition. It rarely develops before age six, and is due to a genetically programmed decline in lactase. This decline begins around age two, the age when most infants have finished the transition from breast milk to solid food. In some people this decline continues to the point where in late childhood or early adulthood they develop lactose intolerance symptoms. Lactose intolerance is strongly linked to race and ethnicity. People of Northern European ancestry have the lowest rate of lactose intolerance, about 5% In Hispanic, Jewish, and Southern European populations, the rate is about 70%, and it reaches 90% or more in Asian and African populations. Worldwide, in adults the inability to digest lactose is much more common
than the ability to digest it. Although the symptoms are similar, lactose intolerance is not the same as cow’s milk intolerance. Cow’s milk intolerance is a food allergy and causes an allergic reaction. Only about 3.4% of Americans have cow’s milk intolerance.
The degree to which people are lactose intolerant varies widely. Some people can drink a glass of milk daily without developing unpleasant symptoms. Others can drink only small amounts of milk at a time, and have fewer symptoms if milk is mixed with food. Some people can eat cheese, ice cream, or yogurt, but cannot drink milk. A few people are 100% lactose intolerant and even the smallest amount of lactose will produce unpleasant symptoms.
Although the greatest quantities of lactose are found in milk and dairy products, milk is used in the preparation of many processed foods such as chocolate bars, puddings, and soups. Food labels must list all the ingredients in processed foods. Lactose intolerant individuals should look for these words on the label that indicate the presence of lactose: milk, condensed milk, whey, curds, milk-by-products, dry milk solids.
Lactose is found in other unlikely places such as:
- bread and baked goods and biscuit, pancake, and cookie mixes
- processed breakfast cereals and breakfast drinks
- instant mashed potatoes
- lunch meats (except kosher meats which are lactose-free)
- salad dressings
- all chocolate candies, caramels, butterscotch, and many others
- as filler in medications. As many as 6% of prescription and over-the-counter drugs contain lactose
The amount of lactose found in these hidden sources is not enough to affect most people, but for the severely lactose intolerant, it can be enough to cause symptoms and make meal planning a necessity and eating out difficult.
Lactose intolerance is treated by eliminating lactose from the diet beyond the level where it produces symptoms. Alternately, enzymes such as LACTAID or Dairy Ease can be added to milk 24 hours before drinking. These enzymes pre-digest lactose and can eliminate 70-99% of it. Lactose-reduced milk is available at many supermarkets. All LACTAID and Dairy Ease milk is 70% lactose-free except for non-fat LACTAID, which contains no lactose. When eating other foods that contain lactose, LACTAID and Dairy Ease capsules are taken at the same time that an individual begins eating. These capsules contain enzymes to help digest lactose.
Since dairy products are the main source of calcium in the standard American diet, people who eliminate milk, cheese, yogurt, and other dairy products must adjust their diet to get enough calcium. Calcium is critical to building and maintaining strong bones and teeth and is needed for metabolic processes such as muscle contraction and nerve impulse transmission.
The United States Institute of Medicine (IOM) of the National Academy of Sciences has developed values for the adequate intake (AI) of calcium. These values are based on age and gender. Some nutritionists and researchers believe that they are too low. The AI values for calcium are listed below.
- children birth-6 months: AI 210 mg
- children 7-12 months: AI 270 mg
- children 1-3 years: AI 500 mg
- children 4-8 years: AI 800 mg
- children 9-13 years: IA 1,300 mg
- adolescents 14-18 years: IA 1,300 mg
- adults age 19-50:IA 1,000 mg
- adults over age 50: IA 1,200 mg
- pregnant women 18 years and younger: IA 1,300 mg
- pregnant women over age 18:IA 1,000 mg
- breastfeeding women 18 years and younger: IA 1,300 mg
- breastfeeding women over age 18: IA 1,000 mg
Some good sources of calcium that do not contain lactose are:
- sardines with bones, canned in oil, 3 ounces: 270-325 mg
- salmon with bones, canned, 3 ounces: 180-205 mg
- tofu, firm, made with calcium sulfate added, 1/2 cup: 204 mg
- pinto or red beans, cooked, 1/2 cup: 43 mg
- white beans, cooked, 1/2 cup: 113 mg
- bok choy, 1/2 cup cooked: 61 mg
- bread, whole wheat, 1 slice: 20 mg
- orange juice, fortified with calcium, 6 ounces: 200-260 mg
- soymilk, 1 cup: 200-300 mg
A dietitian can help the severely lactose intolerant person develop a meal plan that will meet their dietary need for calcium and/or recommend a calcium supplement. Calcium supplements are available over-the-counter at pharmacies and supermarkets.
Lactose intolerance cannot be cured. The purpose of the lactose intolerance diet is to bring the symptoms of bloating, gas, abdominal discomfort, and diarrhea under control so that the individual is comfortable, and the symptoms do not disrupt his or her daily activities.
The benefit of a lactose intolerant diet is that the uncomfortable symptoms of bloating, nausea, stomach cramps, and diarrhea are controlled.
Lactose intolerance is variable. Individuals must work out through trial and error how much and which lactose-containing foods then can eat without stimulating symptoms. During trial and error experimentation, there will be moments of misjudgment when symptoms develop.
The greatest risk to this diet is that the individual will not get enough calcium.
The lactose intolerant diet is accepted by medical professionals as a standard treatment for this condition. The diet has existed for many years and is not controversial.
Field, Tamara. The Milk Soy Protein Intolerance (MSPI) Guidebook/Cookbook New York: Vantage Press, 2001. .
Joneja , Janice V. Dealing With Food Allergies: A Practical Guide to Detecting Culprit Foods and Eating a Healthy, Enjoyable Diet Boulder, CO: Bull Pub., 2003. .
Rockwell, Sally. Calcium Rich & Dairy Free: How to Get Calcium Without the Cow Pomeroy, WA: Health Research Books, 2005. .
Schroeder, Florence E. Cooking Without Milk: Milk-Free and Lactose-Free Recipes. Nashville, TN: Cumberland House Pub., 2002.
American Gastroenterological Association. 4930 Del Ray Avenue, Bethesda, MD 20814, Telephone: (301) 654-2089. Website: <http://www.gastro.org>
International Foundation for Functional Gastrointestinal Disorders. P. O. Box 170864, Milwaukee, WI 53217, Telephone: (888) 964-2001. Fax: (414) 964-7176. Website: <http://www.iffgd.org>
National Digestive Diseases Information Clearinghouse (NDDIC). 2 Information Way Bethesda, MD 20892-3570. Telephone: (800) 891-5389. Fax: (703) 738-4929. Website: <http://digestive.niddk.nih.gov>
Guandalini, Stefano and Richard E. Frye. “Lactose Intolerance.” eMedicine.com, October 3, 2006. <http://www.emedicine.com/ped/topic1270.htm>
Jackson Siegelbaum Gastroenterology. “Lactose-Free Low-lactose Diet.” 2006 <http://www.gicare.pated/edtgs05.htm>
“Lactose Intolerance Diet.” University of Utah Health Science Center. <http://uuhsc.utah.edu/pated/handouts/handout.cfm?id=866>
Medline Plus. “Lactose Intolerance.” U. S. National Library of Medicine, March 22, 2007. <http://www.nlm.nih/gov/medlineplus/actoseintolerance.html>
National Digestive Diseases Information Clearinghouse (NDDIC). “Lactose Intolerance.” March 2006. <http://digestive.niddk.nih.gov/diseases/pubs/lactoseintolerance/index.htm>
Nemours Foundation. “Lactose Intolerance.” September 2006. <http://www.kidshealth.org/teen/food_fitness/nutrition/lactose_intolerance.html>
WebMD. “Lactose Intolerance.” <http://www.webmd.com/digestive-disorders/digestive-diseases-lactose-intolerance.htm>
Tish Davidson, A.M.