I located an URL takes the view - which I have theorized about the enzyme -
that it protects the body from the toxin, alcohol, found in our environment.
However, it also says that it converts it into a useable commodity for our
cells, which would seem to suggest the alcohol-as-food theory...

Marilyn

http://www.scripps.edu/pub/goodsell/pdb/pdb13/pdb13_1.html

Alcohol Dehydrogenase

 Here's a toast to alcohol dehydrogenase. While recovering from the excesses
of New Year's Eve, we might ponder the enzyme that ceaselessly battles the
champagne that we consume. Alcohol dehydrogenase is our primary defense
against alcohol, a toxic molecule that compromises the function of our
nervous system. The high levels of alcohol dehydrogenase in our liver and
stomach detoxify about one stiff drink each hour. The alcohol is converted
to acetaldehyde, an even more toxic molecule, which is then quickly
converted into acetate and other molecules that are easily utilized by our
cells. Thus, a potentially dangerous molecule is converted, through alcohol
dehydrogenase, into a mere foodstuff.

Forms and Functions

Our bodies create at least nine different forms of alcohol dehydrogenase,
each with slightly different properties. Most of these are found primarily
in the liver, including the beta3 form (PDB entry 1htb) pictured here. The
sigma form, available in PDB entry 1agn, is found in the lining of the
stomach. Each enzyme is composed of two subunits, and quite remarkably, you
can mix and match subunits between these different forms, creating mixed
dimers that are still active. Ethanol is not the only target of these
enzymes, they also make important modifications to retinol, steroids, and
fatty acids. The range of different types of alcohol dehydrogenase ensures
that there will always be one that is perfect for the current task.

Consequences

Alcohol dehydrogenase provides a line of defense against a common toxin in
our environment. But this protection carries with it some dangers. Alcohol
dehydrogenase also modifies other alcohols, often producing dangerous
products. For instance, methanol, which is commonly used to "denature"
ethanol rendering it undrinkable, is converted into formaldehyde by alcohol
dehydrogenase. The formaldehyde then does the damage, attacking proteins and
embalming them. Small amounts of methanol causes blindness, as the sensitive
proteins in the retina are attacked, and larger amounts, perhaps a glassful,
lead to widespread damage and death.