How Lactose Intolerance is Diagnosed
The elimination diet is easy to try. To see whether you’re lactose intolerant, just cut out all milk and dairy products, including foods made with milk or other dairy products, for a short period of time — a few days to a week. If your symptoms go away, you may have your answer. You may determine that certain foods bother you more than others.
Your doctor also may decide to conduct other tests to zero in on a diagnosis of lactose intolerance. These tests include the following:
A hydrogen breath test: After drinking a high-lactose beverage, your breath is analyzed over a period of time to check the levels of hydrogen. People who produce lactase have less hydrogen in their breath. People who don’t produce lactase and are lactose intolerant are more likely to have high levels of hydrogen in their breath. The hydrogen is caused when bacteria ferment the undigested lactose in the colon.
A stool acidity test: If you don’t produce lactase and can’t digest lactose, acids and sugar can be detected in a stool sample. This test often is used for infants and young children experiencing digestive problems to help healthcare providers rule out various causes.
Lactose intolerance is uncommon in infants and young children, but babies born prematurely may be affected.
Intestinal biopsy: In this test, the doctor examines a small piece of your intestinal tissue and measures the level of lactase activity.
Genetic testing: Scientists can use genetic testing to determine whether you have the genes associated with production of lactase in adulthood or the genes associated with lactase nonpersistence.
A 2010 report on lactose intolerance and health by the National Institutes of Health concluded that it’s impossible to accurately estimate the number of people in the United States who are affected by lactose malabsorption or lactose intolerance. In part, that’s because studies have been inconsistent in the way they define the condition. The bottom line is that the majority of the world’s adults are affected — whether they have symptoms or not — because many humans aren’t designed to digest milk after infancy.
The number of lactose intolerant people in the United States is likely to grow in the coming years. Census data shows that the nonwhite minority in the United States is going to be a majority by the year 2050. People in this minority are the most likely to be lactose intolerant.