Editing Lactose intolerance (section)

== Epidemiology ==
[[File:Lactose tolerance in the Old World.svg|thumb|upright=1.4|An estimate of the percentage of adults that can digest lactose in the indigenous population of the Old World<ref name="Itan et al. 2010"/>]]
Worldwide, about 65% of people experience some form of lactose intolerance as they age past infancy, but there are significant differences between populations and regions. As few as 5% of northern Europeans are lactose intolerant, while as many as 90% of adults in parts of Asia are lactose intolerant.<ref name=GHR2016>{{cite web|title=Lactose intolerance|url=https://ghr.nlm.nih.gov/condition/lactose-intolerance|website=Genetics Home Reference|access-date=18 November 2016|url-status=live|archive-url=https://web.archive.org/web/20161119060547/https://ghr.nlm.nih.gov/condition/lactose-intolerance|archive-date=19 November 2016}}</ref>

In northern European countries, early adoption of dairy farming conferred a selective evolutionary advantage to individuals that could tolerate lactose. This led to higher frequencies of lactose tolerance in these countries. For example, almost 100% of [[Irish people]] are predicted to be lactose tolerant.<ref name="Itan et al. 2010"/> Conversely, regions of the south, such as Africa, did not adopt dairy farming as early and tolerance from milk consumption did not occur the same way as in northern Europe.<ref name="SilanikoveLeitner2015" /> Lactose intolerance is common among people of Jewish descent, as well as from West Africa, the Arab countries, Greece, and Italy.<ref name=GHR2016/> Different populations will present certain gene constructs depending on the evolutionary and cultural pre-settings of the geographical region.<ref name="SilanikoveLeitner2015" />