When ancient cultures started eating grain, people with the genes for celiac disease may have had better protection against tooth decay. Italian scientists think this finding might explain why the disease is so common today.
Many civilizations have depended on wheat since it was first cultivated in the Middle East 10,000 years ago. No one knew that wheat gluten caused celiac disease until the 20th century. But ancient bones and medical reports indicate that people suffered and died from it long ago. Theoretically, wheat-based diets should have killed more people who carried celiac disease genes, reducing their prevalence in later generations.
Paradoxically, these genes are most common in cultures with a long wheat-growing history, from the Middle East to Western Europe, parts of India and North Africa. The Italian study strengthened this connection and found that the most common celiac disease gene, HLA-DQ2, correlates with wheat consumption in 24 countries.
What advantage could favor its survival? Previous research found that tooth decay is the only thing the gene for celiac disease might prevent. A 2012 Brazilian study found that adolescents who carry HLA-DQ2 are less prone to tooth decay. Other research has found that, even though untreated celiac disease patients are prone to defective enamel, they are less likely than healthy people to have tooth decay.
The Italian authors speculate that the gene might provide code for a mechanism to clear the sticky protein from the mouth. This ability would have been a big advantage long ago. When people started consuming more carbohydrates, tooth decay for the first time became a serious problem. Cure and prevention were nonexistent, so people with natural tooth protection from gluten-fighting genes might have had an advantage for survival.
Lionetti, E. and Catassi, C. “Co-localization of gluten consumption and HLA-DQ2 and –DQ8 genotypes; a clue to the history of celiac disease,” Digestive and Liver Disease, 2014, doi:10.1016/j.dld.2014.08.002.