Lactose Intolerance


Lactose intolerance is the inability to digest significant amounts of lactose, the major sugar found in all forms of milk or products derived from cows including fat free cows milk. Lactose intolerance is caused by a shortage of the enzyme lactase, which is produced by the cells that line the small intestine. Lactase breaks down milk sugar into two simpler forms of sugar called glucose and galactose, which are then absorbed into the bloodstream. Not all people deficient in lactase have the symptoms commonly associated with lactose intolerance, but those who do are said to have lactose intolerance.

People sometimes confuse lactose intolerance with cow’s milk intolerance because the symptoms are often the same. However, lactose intolerance and cow’s milk intolerance are not related. Being intolerant to cow’s milk is an allergic reaction triggered by the immune system. Lactose intolerance is a problem caused by the digestive system. Close to 50 million American adults are lactose intolerant.


What causes lactose intolerance?

Some causes of lactose intolerance are well known. Primary lactase deficiency is a condition that develops over time. After about age 2 the body begins to produce less lactase, though most people will not notice symptoms until they are much older.

Secondary lactase deficiency occurs when injury to the small intestine or certain digestive diseases reduce the amount of lactase a person produces. These diseases include celiac disease, inflammatory bowel disease, and Crohn’s disease.

Researchers have identified a genetic link for lactose intolerance. Some people are born with a likelihood of developing primary lactase deficiency because it has been passed to them genetically (inherited from their parents).

Who is at risk for lactose intolerance?

Between 30 and 50 million Americans are lactose intolerant and certain ethnic and racial populations are more affected than others. Up to 80 percent of African Americans, 80 to 100 percent of American Indians, and 90 to 100 percent of Asian Americans are lactose intolerant. The condition is least common among people of northern European descent.


Common Symptoms Include:

  • Nausea
  • Cramps
  • Bloating
  • Gas
  • Diarrhea

Symptoms 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. 

How is lactose intolerance diagnosed?

Lactose intolerance can be hard to diagnose based on symptoms alone. People sometimes think they suffer from lactose intolerance because they have the symptoms associated with the disorder, not knowing other conditions such as irritable bowel syndrome can cause similar symptoms. A doctor can use tests to diagnose lactose intolerance but may first recommend eliminating cow’s milk from the diet to see if the symptoms go away.


Tests Used to Detect Lactose Intolerance

Lactose intolerance can be hard to diagnose based on symptoms alone. People sometimes think they suffer from lactose intolerance because they have symptoms associated with the disorder, not knowing that other conditions, such as irritable bowel syndrome, can cause similar symptoms. 
Noting your body’s response to lactose restriction may be sufficient to diagnose lactose intolerance. A gastroenterologist can also use tests to determine if you’re lactose intolerant.

Lactose tolerance test: Given to older children as well as adults. Before the test, patients fast (do not eat) and blood is drawn to measure the fasting blood glucose (blood sugar) level. Patients then drink a large amount of a liquid that contains lactose. Blood samples are taken over a two¬hour period to determine glucose levels, which tell how well the body is able to digest lactose.

Hydrogen breath test: Measures the amount of hydrogen in the breath. Normally, very little hydrogen is detectable in the breath. However, undigested lactose leads to the formation of various gases, including hydrogen, by bacteria in the colon. 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. Hydrogen in the breath means improper digestion of lactose. Certain foods, medications, and smoking can affect the test’s accuracy and may need to be avoided before the test.

Controlling Symptoms

No known way exists to increase the amount of lactase enzyme the body can make, but symptoms can be controlled through diet. 
Small children born with lactase deficiency should not be fed any foods containing lactose. Most older children and adults do not need to avoid lactose completely, but individuals differ in the amounts of lactose they can handle.  Dietary control of the problem depends on each person’s knowing, through trial and error, how much milk sugar and what forms of it your body can handle.

Check out our Lactose Free diet for food and nutrition specifics.

Watch for Hidden Lactose

Although milk and foods made from milk are the only noteworthy natural sources, lactose is often added to prepared foods. It is important for people with very low tolerance for lactose to know about the many foods that contain lactose, even in small amounts, including:

  • 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 “nondairy” products, such as powdered coffee creamer and whipped topping, may include ingredients that are derived from milk and therefore contain lactose. It is important to read the food label.

Read Food Labels

Learn to recognize the following ingredients that may contain.  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 contain lactose, as do some tablets for stomach acid and gas. A pharmacist can answer questions about the amounts of lactose in various medicines.