Recently my wife has developed what appears to be a case of lactose intolerance, where the body no longer produces the enzyme lactase necessary to break down lactose, the main sugar found in milk. I’ve done some reading up on the subject, and have come across many articles about how most of humanity is classifiable as “lactose intolerant”.
These articles often cite very similar and uncited statistics stating that the occurence of “LI” is something like 90% among people of Asian descent, 70% among people of African descent, and so on down to around 20% among people of European descent. There are often accompanying statistics about how the groups with the highest occurences (Asians and Africans) also typically develop the intolerance at earlier ages. The unstated assumption is that lactose intolerance is genetically determined.
There is simply no way that 90% of the Asian-Americans, 70% of the African-Americans, etc. of my acquaintance are lactose intolerant in the way that my wife currently is. I grew up in New York City, where dairy products are routinely consumed everywhere: cheese on pizza, butter or cream cheese on bagels, milk in Starbucks lattes (and provided every school day), ice cream from Mister Softee, etc. These foods were eaten across the entire ethnic spectrum of people I grew up and work with, which is pretty much the ethnic spectrum of the world. I don’t remember anybody having to scarf Lactaid pills or avoiding pizza due to lactose intolerance.
Even my parents, who immigrated from China in their 30s, can eat pizza or ice cream when the fancy takes them without running to the bathroom within a few hours.
This leads me to conclude one or more things are true:
[ul]These statistics were basically made up or based on dubious samplings at some earlier point in time, and have since been cribbed and propagated as fact without citation by various writers. (I understand that this accounts for up to 45% of quoted statistics on the Internet.)
[ul]The 90% figure for Asians and 70% for Africans is accurate for populations in Asia and Africa, and that the continued consumption of milk products throughout one’s life (as in a Western culture) is the main factor responsible for continuing to be able to produce lactase.
[ul]The definition of “lactose intolerance” used for the very high incidence rates is stretched out to the point of uselessness. Several sites mentioned that a milder form, “lactose deficiency”, generally meant that people could eat varying quantities of dairy without ill effect. If the litmus test is having a problem with drinking, say, a gallon of milk at a sitting, who really cares?[/ul]
Anybody with comments or insights?