Only certain East Asian populations have a high prevalence of a gene that protects against alcohol overconsumption, and researchers speculate that some event must have occurred over the past few thousand years to make this genetic protection advantageous, Reuters reported April 23.

Yale University researchers said that unknown environmental factors ar the likely cause for the prevalence of the ADH1B*47His gene variant among some Asian populations, but not others. The gene causes rapid metabolism of alcohol into acetaldehyde, a chemical that produces hangovers, flushing, nausea and other unpleasant symptoms that make even moderate drinking a poor experience.

Researchers found that the gene variant was very prevalent in East Asia, fairly common in West Asia and North Africa, and rare in other parts of the world. In Asia, the gene was most common among speakers of the Hmong and Altaic languages. Within these groups, environmental factors apparently made survival more likely among individuals with the gene than those who lacked the variant.

However, researchers doubt that protection against alcoholism was the key to survival, noting that consumption of highly concentrated forms of alcohol is a relatively recent phenomenon. One possibility is that the gene protected these populations from toxins in their traditional foods that was not present in the diets of other populations.

The study was published in the journal PLoS One.