The ADH1B gene is located on chromosome 4q21–q23. Naturally occurring single nucleotide polymorphisms (SNPs) may be capable of altering ethanol metabolism(4). One common form of a SNP (rs1229984 or Arg48His in exon 3) is ADH1B Arg (previously referred to as *1). The ADH1B His (*2) allele encodes a super-active allozyme, which has been reported to be associated with lower rates of AD in numerous association studies. ADH1B His is common among Asian populations and moderately common in Russian and Jewish populations, but rare in western and central Europeans(5). In some African and Mexican populations rs2066702 (Arg370Cys, previously designated ADH1B *3) is observed. On the other hand, some individuals with a high daily intake of alcohol develop alcohol-induced diseases, and a proposed mechanism is that the His allele (or Cys allele) can increase the level of acetaldehyde after a certain dose of ethanol, and then result in enhanced objective and subjective negative reactions to alcohol, which would in turn reduce the likelihood of habitual alcohol use, AD, and alcohol-induced liver diseases.
