It has long been understood that excessive drinking of alcohol can lead to serious impairments in various organs including the liver and brain. However, it is now become clear that there is a real risk associated with chronic consumption of alcohol(ethanol) with increased risk of getting certain kinds of cancers including upper aerodigestive tract, the liver, the large intestine and the female breast.
In a recent paper that appeared in the journal Science, the
etiology of this relationship has been demonstrated. Multiple mechanisms have been elaborated to
explain this relationship. According to
the authors, “Among those the action of acetaldehyde (AA), the first metabolite
of ethanol oxidation is of particular interest.
Structure of
Acetaldehyde – Black – Carbon; White – Hydrogen; Red - Oxygen
“AA is toxic, mutagenic and carcinogenic in animal
experiments. AA binds to DNA and forms
carcinogenic adducts. Direct evidence of
the role of AA in alcohol-associated carcinogenesis derived from genetic
linkage studies in alcoholics. Polymorphisms
or mutations of genes coding for AA generation or detoxifying enzymes resulting
in elevated AA concentrations are associated with increased cancer risk. Approximately 40% of Japanese, Koreans or
Chinese carry the AA dehydrogenase 2*2 (ALDH2*2) allele in its heterozygous
form. This allele codes for an ALDH2
enzyme with little activity leading to high AA concentrations after the
consumption of even small amounts of alcohol. When individuals with this allele consume
ethanol chronically, a significant increased risk for upper alimentary tract
and colorectal cancer is noted. In
Caucasians, alcohol dehydrogenase 1C*1 (ADH1C*1) allele encodes for an ADH
isoenzyme which produces 2.5 times more AA than the corresponding allele
ADH1C*2. In studies with moderate to
high alcohol intake, ADH1C*1 allele frequency and rate of homozygosity was
found to be significantly associated with an increased risk for cancer of the
upper aerodigestive tract, the liver, the colon and the female breast. These studies underline the important role of
acetaldehyde in ethanol-mediated carcinogenesis.”
This article elaborated further,” Acetaldehyde is highly
toxic, mutagenic and carcinogenic. AA
interferes at many sites with DNA synthesis and repair and can, consequently,
result in tumor development [6, 7]. Numerous
in vitro and in vivo experiments in prokaryotic and eukaryotic cell cultures as
well as in animal models have shown that AA has direct mutagenic and
carcinogenic effects.”
In conclusion, these data strongly reinforce the nature of
the relationship between the chronic
drinking of ethanol and certain cancers.
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