ALDH2 Lys/Glu heterozygotes experience a less severe manifestation of the flushing response due to residual but low ALDH2 enzyme activity in their cells. As a result, some are able to develop tolerance to acetaldehyde and the flushing response and become habitual heavy drinkers, due in part to the influence of societal and cultural factors (see below). Therefore, paradoxically, it is the more common low-activity ALDH2 heterozygous genotype that is associated with greatest risk of esophageal cancer from drinking alcohol.
