About 60 percent of people in the world are lactose intolerant, primarily those in Asia and Africa. In the U.S., there are between 30 million and 50 million lactose intolerant people, with about 90 percent of people of Asian heritage being lactose intolerant and up to 75 percent of African Americans and American Indians being lactose intolerant. The country with the lowest percentage of lactose intolerant people is Denmark, where only about 2 percent of the population is lactose intolerant. Zambia is the country with the highest percentage of lactose intolerant people — almost 100 percent.
More facts about lactose intolerance:
- Lactose intolerance is caused by the failure to produce the enzyme lactase in the body. Without this enzyme, the body can't break down lactose products, which can lead to cramping, diarrhea, nausea and acid reflux.
- Though almost all humans can digest milk properly as babies, about 60 percent lose the ability to produce lactase as they grow older. In China and Japan, people tend to lose 20-30 percent of their lactose-digesting ability within the first four years after being weaned.
- People who are descended from ethnic groups that historically raised or relied on cattle as a food source typically have a much lower incidence of lactose intolerance, though this is not always the case. In many instances, societies made of primarily lactose intolerant people live next to primarily lactose tolerant people, mostly in parts of Africa and the Middle East.