page_title: Lactose intolerance
section_title: Epidemiology
hierarchical_section_title: Lactose intolerance / Epidemiology
caption_attribution_description: English: Worldwide prevalence of lactose intolerance in recent populations. An average of all ethnic groups of the total population of a country is represented. Because of sometimes poor data situation partly extrapolated.[1]
context_page_description: Lactose intolerance is a decreased ability to digest lactose, a sugar found in dairy products. Those affected vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pain, bloating, diarrhea, gas, and nausea. These symptoms typically start thirty minutes to two hours after eating or drinking milk-based food. Their severity typically depends on the amount a person eats or drinks. Lactose intolerance does not cause damage to the gastrointestinal tract.
  Lactose intolerance is due to the lack of the enzyme lactase in the small intestines to break lactose down into glucose and galactose. There are four types: primary, secondary, developmental, and congenital. Primary lactose intolerance occurs as the amount of lactase declines as people age. Secondary lactose intolerance is due to injury to the small intestine. Such injury could be the result of infection, celiac disease, inflammatory bowel disease, or other diseases. Developmental lactose intolerance may occur in premature babies and usually improves over a short period of time.
context_section_description: Overall, about 65% of people experience some form of lactose intolerance as they age past infancy, but there are significant differences between populations and regions, with rates as low as 5% among northern Europeans and as high as over 90% of adults in some communities of Asia.
  Some populations, from an evolutionary perspective, have a better genetic makeup for tolerating lactose than others. In northern European countries, lack of Vitamin D from the sun is balanced by consuming more milk and therefore more calcium. These countries' people have adapted a tolerance to lactose. Conversely, regions of the south, such as Africa, rarely experienced Vitamin D deficiency and therefore tolerance from milk consumption did not develop the same way as in northern European countries. Lactose intolerance is common among people of Jewish descent, as well as from West Africa, the Arab countries, Greece, and Italy. Different populations will present certain gene constructs depending on the evolutionary and cultural pre-settings of the geographical region.
caption: Rough rates of lactose intolerance in different regions of the world
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