What is lactose intolerance?
Lactose is the sugar in milk products. Individuals who are lactose intolerant lack the enzyme or chemical (lactase) to break down this sugar for absorption. As a result, lactose gets into the large bowel (colon) and may cause gas, bloating, diarrhea and abdominal cramping. Sometimes lactose intolerance occurs after digestive infections.
Lactose intolerance affects more than 7 million Canadians. This is likely an underestimate as many individuals do not associate their symptoms with lactose-containing foods or are asymptomatic.
Signs & Symptoms of lactose intolerance
The simplest, and probably most reliable, way of diagnosing whether an individual is lactose intolerant or not is to remove all lactose products from the diet for 1 to 2 weeks and see if the symptoms resolve.
There are other tests available when the response to lactose exclusion is not clear. A blood test is readily available but probably is not needed if a trial of lactose avoidance is attempted.
How to test for lactose intolerance?
The simplest, and probably most reliable, way of diagnosing lactose intolerance is to remove all lactose products from your diet for 1 - 2 weeks and see if your symptoms disappear. If the symptoms do disappear, a diet that does not include lactose should be maintained.
There are other tests available when the response to lactose exclusion is not clear. These include blood tests, hydrogen breath test and stool acidity test for young children.
Treating lactose intolerance
If a person is lactose intolerant, the best treatment is to avoid dairy products. Many people with lactose intolerance will be able to enjoy milk, ice cream and other dairy products if taken in small amounts or with other food. Hard cheeses and yogurt may be tolerated better than other dairy products.
There are lactase enzymes available both in the pharmacy and health food stores which help minimize the effects of lactose intolerance. The commercially-produced, lactose-reduced milks are usually quite reliable and are well tolerated, as are milk substitutes such as rice milk or soya milk.
Milk products are the primary sources of calcium and vitamin D. Anyone who avoids milk products should take calcium (1 gram) and vitamin D (400 units) supplementation assuming an otherwise normal diet. Patients with difficult or persistent problems may benefit from seeing a registered dietitian.
Frequently asked questions on lactose intolerance
I have stopped drinking milk, eating cheese and ice cream but still have symptoms sometimes. Why is that?
The reason could be that you are still unknowingly ingesting milk products. Milk and milk products are often added to processed food. Products that list whey, dry milk solids, dry milk powder, whey, curds contain lactose. Be sure to check the ingredients on food labels to see if there is lactose in food products that are not obviously milk-based.
If my child is lactose intolerant, what can he eat to be sure he gets calcium in his diet?
Non-milk products that contain calcium include rhubarb, spinach, broccoli, salmon, sardines, soy milk and oranges among others. It is a good idea to speak with a nutritionist or dietitian if you or someone in your home is lactose intolerant.
Is it possible that I have celiac disease as well as lactose intolerance?
It is possible. 25% of patients who have been clinically identified as lactose intolerant, have celiac disease. In Canada, that means about 73,500 people have undiagnosed celiac disease which is the causal agent for their lactose intolerance. If you think you have celiac disease, you should speak with your doctor.
Is lactose intolerance the same thing as being allergic to milk?
No. When people are allergic to milk, their body’s immune system reacts to one or more milk proteins. Milk allergies can be life threatening even if a small amount of milk or milk product is consumed. Milk allergies are generally diagnosed in the first year of life, while lactose intolerance occurs more often in adulthood.
Statistics on lactose intolerance
- Lactose is a natural sugar found in milk. Individuals who are lactose intolerant lack the enzyme (lactase) to break down this sugar for absorption. Lactose then gets into the large bowel (colon) and may cause gas, bloating, diarrhea and abdominal cramping. Sometimes lactose intolerance occurs after digestive infections.
- Lactose intolerance is associated with lower quality of life. (Casellas et al. 2016)
- The true prevalence of lactose intolerance is unknown. In a national Canadian survey, 16% of participants perceived that they had lactose intolerence. (Barr 2013)
- Lactose intolerance is more prevalent among African Americans, Hispanic Americans, Asian Americans, and Native Americans, and less common among those of European descent. (Suchy et al. 2010)
- Elimination of milk and milk products is not necessary in lactose intolerance. In general, individuals may tolerate at least 12 g of lactose when administered in a single dose (equivalent to the lactose content in 1 cup of milk). Larger amounts of lactose may be tolerated if ingested with meals and distributed throughout the day. (Suchy et al. 2010)
Barr SI. Perceived lactose intolerance in adult Canadians: a national survey. Appl Physiol Nutr Metab. 2013 Aug;38(8):830-5.
Casellas F et al. Perception of lactose intolerance impairs health-related quality of life. Eur J Clin Nutr. 2016 Sep;70(9):1068-72.
Suchy FJ et al. NIH consensus development conference statement: Lactose intolerance and health. NIH Consens State Sci Statements. 2010 Feb 24;27(2):1-27.