Primary lactose intolerance: It is experienced when the body decreases production of lactase with age.
Secondary lactose intolerance: It is experienced as a result of illness.
Congenital lactose intolerance: It is hereditary and very rare when a baby is born with lactose intolerance
This article will focus on primary lactose intolerance resulting from a decreased production of lactase. This decrease in lactase production appears to be genetically programmed. For example, although all Asian people are lactose intolerant, they may tolerate to dairy products in childhood. However, they begin to develop symptoms of lactose intolerance by 5 years of age. In African American children, lactose intolerance develops by 10 years of age, and in Caucasian people by young adulthood.
Approximately 70% of the world’s population has primary lactase deficiency. The prevalence varies according to ethnicity, as well as the availability of dairy products in the diet. In populations with an abundance of milk products in the diet, especially among people of Northern Europe, the incidence of lactose intolerance may be as low as 2%, while 100% of the Asian population, 80% of Native Americans, and 70% of Blacks are lactose intolerant.
Lactase is an enzyme produced in the small intestine and is responsible for the breakdown of lactose, the major milk sugar. As the undigested lactose passes from the small intestine into the colon, certain bacteria found there break it down, releasing hydrogen and/or methane in the process. These gases are responsible for the uncomfortable symptoms that lactose intolerant sufferers may experience after eating dairy products:
The severity of symptoms of lactose intolerance vary, depending on the amount of lactose in the diet and the amount of lactase in an individual’s digestive system. Everyone can respond differently to lactose.
How is it diagnosed?
Symptoms of lactose intolerance are common to other digestive system disorders. Therefore, if you suspect that you might have lactose intolerance, talk to your health care provider. She or he may order lab work to rule out a serious Irritable Bowel disease. To confirm the diagnosis of lactose intolerance, your health care provider may suggest the lactose tolerance test, the hydrogen breath test, or the stool acidity test.
The Lactose Tolerance Test
Fasting before this test is required. At the beginning of the test, the patient drinks liquid containing the equivalent of lactose in two cups of milk. Over a period of 2 hours, blood samples are drawn to assess how well the body digests lactose.
In healthy people, when lactose reaches the small intestine, lactase breaks it down into glucose and galactose. The liver breaks down galactose into glucose that enters the bloodstream. Hence, after ingestion of lactose, there should be an elevation of glucose in the bloodstream. However, if lactose is not completely broken down, a rise in blood glucose level does not occur. This finding serves as a confirmation of lactose intolerance.
The Hydrogen Breath Test
This test measures levels of hydrogen in a person’s breath. Healthy people do not exhale large amounts of hydrogen. In people with lactose intolerance, as lactose passes from the small intestine into the colon and bacteria begin breaking it down, hydrogen and/or methane are produced. Those gases are absorbed by the bloodstream and carried to the lungs.
The patient drinks liquid containing lactose, and their breath is analyzed at regular intervals. Higher levels of hydrogen and/or methane in the breath confirm the diagnosis of lactose intolerance.
The Stool Acidity Test
This test can be performed on infants and children, because the previous two tests require ingestion of large amounts of lactose that may lead to diarrhea and thus dehydration. The stool acidity test measures the amount of acid in the stool. When undigested lactose passes the digestive system, lactic acid is released into the stool. Therefore, the stool’s acidity increases.
How is it managed?
Lactose intolerance is easily managed through dietary manipulation. Avoidance of foods with lactose will result in symptom resolution. To assure appropriate amount of calcium in the diet, it is crucial to include in the diet calcium-rich products, such as calcium-fortified lactose-free milk, soymilk, or calcium-fortified juice. Most lactose intolerant people can tolerate some lactose in their diet. Therefore, they should find out through trial and error the acceptable amount of dairy and include it in their diet. Studies show that dietary lactose enhances calcium absorption, and conversely, lactose-free diets result in lower calcium absorption. Thus, daily consumption of the tolerable amount of dairy is crucial to the optimal bone health.
Those who react to small amounts of lactose may try a lactase enzyme available over-the-counter. It is available in tablets and drops and is taken with the first bite of the lactose-rich food.
Hidden sources of lactose
Bread, pastries, and other baked goods
Instant potatoes, soups
Consider these tips to limit the effects of lactose intolerance and enhance your quality of life:
If you continue to drink real milk, drink less, but more often. Also, drink real milk with your meals, as it slows the digestive process and you reduce the chance for symptoms.
Not all dairy products are created equal! The amount of lactose in dairy products vary. For example, Swiss and cheddar cheese have small amounts of lactose and they generally do not cause symptoms
Buy lactose-free products
Watch out for hidden lactose!
Seek alternative sources of calcium (Read Dr. Hillary's article Calcium: Are You Getting Enough?)
Use lactase enzyme drops or tablets before meals to help with digestion of lactose
Try probiotics – bacteria that help to maintain health intestinal flora
Check out my cookbook: Lactose Free and Loving It for some great recipes!
Helpful dining out tips can be found here.
Check out our list of dairy-free menu items at some of the most popular US restaurants to make eating out even simpler! Lactose Free Restaurant Menus.