In searching for possible explanations for the differing alcoholism rates in Indo- and Afro-Trinidadians, researchers have examined the prevalence of various alleles of the alcohol- and acetaldehyde-metabolizing enzymes. One such study found a significant difference in the distribution of alleles of the gene that codes for a type of ADH called ADH1C. One allele of that gene, labeled ADH1C*2, encodes an ADH1C enzyme with somewhat reduced activity compared with the enzyme encoded by the ADH1C*1 allele. Montane-Jaime and colleagues (2006) found that 44 percent of Indo-Trinidadians had one ADH1C*2 and one ADH1C*1 allele (i.e., were heterozygous), and 5 percent carried two ADH1C*2 alleles (i.e., were homozygous).1 In contrast, only 23 percent of Afro-Trinidadians studied had one ADH1C*2 allele and only 1 percent were homozygous. The allele was significantly associated with alcohol dependence—that is, people with at least one ADH1C*2 allele were at higher risk of developing alcohol dependence than people without the allele. Finally, alcoholics with at least one ADH1C*2 allele had significantly elevated levels of certain liver enzymes (i.e., alkaline phosphatase and gamma-glutamyltransferase) that are frequently associated with heavy drinking and alcoholic liver disease. Or conversely, it appears that the ADH1C*1 allele has a protective effect, particularly in Indo-Trinidadians.
