Freakonomics discusses Gluten and celiac Disease.
old NYTimes article HERE.
both overdiagnosed (thanks to a sensitive lab test, mild cases are now being diagnosed) and under diagnosed (a lot of mild cases of irritable bowel disease probably never got diagnosed in the past).
the gene varies in different populations
CD has a worldwide distribution, being described in different ethnic groups from North and South America, Europe, south and west Asia, Australia and New Zealand[6,7]. The disease is rare among Africans and not expected among populations with no HLA DQ2, like Chinese and Japanese, except in individuals presenting HLA DQ8.
west Asia and south Asians do have the problem.
but the low incidence in China might be from under diagnosis, or dietary, but the disease can be found in those with irritable bowel syndrome.
This article suggests it is "rampant" and blames the westernization of the diet, (i.e. less breast feeding, earlier weaning, and the increased use of bread instead of rice in the diet) and notes that it is more common in areas with Caucasian genes (western China... they are presumably discussing the Uighur, who are Turkish in origin).
what you have to realize is that in places with primitive water supplies, diarrhea in children is common, and is indeed one of the major causes of death in young children. So a child with failure to thrive and diarrhea would just die, and everyone, including doctors, would assume it was from the many diarrhea causing diseases in the environment.
But now, with clean water, such cases are rare, so a child with constant diarrhea and failure to thrived would be seen by doctors and checked for food intolerance, including lactose deficiency and celiac disease.
a full review of the history of the disease can be read here.
this map from Dr Shar Institute shows incidence, but note all the blank areas.
|a new epidemiology of celiac disease, characterized by growth in the traditional fields and spread into new regions of the world|
just like previous studies showed the disease was rare in Asia, but is now being diagnosed, one wonders about the low rate in Africans. Again, unsafe water supplies lead to lots of diarrhea deaths, and diarrhea from protein deficiency due to earlier weaning and/or using a baby bottle but not being able to afford powdered milk.
So who has money for an expensive lab test when children are more likely to die from norovirus, measles or malaria?
but as Africa follows Asia out of rural poverty to urban living, one suspects it will be found to be much more common, and it will be diagnosed more often.
and replacing traditional diets of sorghum, maize and rice in some areas with wheat based food might make cases more common.
Rice is, of course, gluten free, and might be one reason that so few cases of celiac disease were seen in rice eating areas, but what about maize, which is a staple in many areas, i.e. East Africa, Latin America?
Ironically, that is unclear: most lay sites say avoid it, but it seems to be less problematic.
This article says maybe
Hypothetically, maize prolamins could be harmful for a very limited subgroup of CD patients, especially those that are non-responsive, and if it is confirmed, they should follow, in addition to a gluten-free, a maize-free diet.