“Several genes code for the ALDH enzyme, including the ALDH2 gene. Two variants of the ALDH2 gene exist. The ALDH2*1 variant produces a functional enzyme, whereas the ALDH2*2 produces an inactive enzyme. Each person inherits two copies of the ALDH2 gene, one from the father and one from the mother. People who inherit two copies of the ALDH2*2 or one copy of the ALDH2*1 gene and one copy of the ALDH2*2 gene produce an impaired ALDH enzyme and are susceptible to the flushing reaction. Because they experience the unpleasant flushing reaction, these people may consume less or no alcohol and therefore be at reduced risk for alcoholism.” (Makimoto, 1998)The reason that Asian populations have a higher occurrence of flushing and other unpleasant side effects is that the inactive gene ALDH2*2 is more commonly found in people of Asian descent. Although Asians are not the only ethnic group to have one or more of the ALDH2*2 gene they are up to 50% more likely to have it than Caucasians. It follows that in order to avoid the unpleasant effects of flushing Asians would be more likely to abstain from drinking or to drink less. This can be seen as a protection against alcoholism that is found predominantly in Asian populations. An interesting aspect of the incidence of alcoholism found in populations where flushing is prevalent is that of those alcoholics found, all of them were heterozygous. In a test of 50 Chinese alcoholics in Taipei 12% had the ALDH2*2 allele. The fact that none of them had 2 ALDH2*2 alleles leads researchers to believe that possessors of homozygous ALDH2*2 alleles have such a strong flushing reaction that they are prevented from becoming alcoholic. It is apparent that the ALDH2*2 allele is instrumental in preventing alcoholism in Asian cultures (Thomasson and Li, 1993). What remains a mystery is why Asian populations are apparently the only ones to benefit from the selection for the ALDH2*2 allele. Anoth...
