Who Is Affected by Lactose Intolerance?
If you are lactose intolerant, you are certainly not alone. About 70% of the world’s population is lactose intolerant, including between 30 and 50 million North Americans.1,4 In Canada, about 1 million women and 400,000 men suffer from the symptoms of lactose intolerance.1
Lactose intolerance develops over time and is often a normal part of aging.1 Lactase levels are high at birth in all infants, regardless of race or ethnicity.6 Worldwide, humans lose 90 to 95 percent of their birth lactase levels by early childhood, and lactase levels continue to decline with increasing age.5 Premature babies are more likely to be lactose intolerant because lactase levels do not increase until the third trimester of pregnancy.3
The age of onset and the prevalence of lactose intolerance differ among ethnic groups. In many populations, the body’s production of lactase peaks at around the age of two, after which lactase levels start to decline,6 although most people will not notice symptoms until they are much older.3 About 20% of Hispanic, Asian, and African American children younger than 5 years are lactose intolerant, while Caucasian children do not usually develop symptoms of lactose intolerance until after the age of 4 or 5.4 Some individuals produce sufficient amounts of lactase all their lives and have no problem digesting lactose.7
Lactose intolerance is least common among people of northern European origin, who have a lactose intolerance prevalence of only about 2 percent.6 Individuals of African or Asian descent, as well as Aboriginal North Americans, are particularly susceptible to developing lactose intolerance.1 The prevalence of lactose intolerance in different multicultural groups is shown below.7
| Multicultural Group | Persons with Lactose Intolerance (%) |
| Asian | 90 |
| African | 80 |
| Native | 62-100 |
| Hispanic | 53 |
| Caucasians | 15 |
Lactose intolerance can also develop in individuals if the small intestine is injured or damaged. Persons recovering from viral or bacterial infections, abdominal surgery, radiation therapy, chemotherapy, or even those who have taken certain types of antibiotics, may temporarily or permanently become lactose intolerant.8,9
