It's known that regular alcohol use - even at moderate levels - can increase the chances of developing various types of cancer.

After several decades of research, the increase in risk is now widely accepted to account for around 3.5% of cancer deaths worldwide. ( ref. Wikipedia )

The exact biological mechanism(s) which cause this increase have not yet been identified.

It's currently thought that the increased risk may be due to toxic breakdown products of alcohol, rather than the alcohol itself.

Much of the ongoing research is focusing on acetaldehyde, the first and most toxic metabolite of alcohol.

Although the exact mechanism of ethanol-associated carcinogenesis still remains unknown, a number of factors may contribute to the development of alcohol-associated cancer, including ethanol metabolising enzymes.

Source : Human Genomics, 3(2):101-102

Also see : Alcohol and ageingplugin-autotooltip__plain plugin-autotooltip_bigAlcohol and ageing

The length of an individual's 'telomeres' - buffer caps which mark the beginning and end of the DNA sequences of chromosomes - have been used as a measure of actual physical 'ageing' (as opposed to measurement in years). [ * see note below ] and Alcohol and the cardiovascular systemplugin-autotooltip__plain plugin-autotooltip_bigAlcohol and the cardiovascular system

"Light-to-moderate drinkers tend to display an overall better cardiovascular health and longevity compared with abstainers or heavy drinkers (Klatsky et al., 1981; Maskarinec et al., 1998; Gaziano et al., 2000; Maraldi et al., 2006).