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Alcoholic beverages and human responses

Được đăng lên bởi 187022106
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ALCOHOLIC BEVERAGES
AND HUMAN RESPONSES
Alcoholic beverages are, in essence, flavored solutions of
ethanol. The flavors may come from grains, as in beer; or
from grapes and other fruit, as in wine; or from any source
of carbohydrates, grains, sugar, or grapes, as in whiskey,
rum, and brandy. In addition, consumers may add their
own flavors, as lime with some beers or fruits with some
wine or carbonated sodas with distilled spirits. The spectrum of flavors is wide indeed. But the purpose of drinking
any of these is to supply ethanol in measured doses to the
user.
Ethanol is as unique as humanity itself. It is a food but
requires no digestion. It acts on many organs in the body
but has no cellular receptors as do all other drugs. It is
stable in the atmosphere to any chemical change, whereas
all other foods will undergo some kind of decomposition. It
is the only food produced solely by microbial action. It enters any cell in the body, freely, without any transport
mechanism. All other foods (and all other substances except water) require a transport mechanism to enter any
cell. It provides energy more rapidly than any other food.
This article inquires more closely into these and other
aspects of ethanol. Although alcohol is a generic term for
a large group of related substances, so common is ethanol
that the term alcohol has been usurped for it and will be
used here from now on to mean ethanol. So common is the
drinking of alcoholic beverages that the word drink or
drinker implies the drinking of alcoholic beverages and not
any others.
People have always needed a release from reality. From
earliest recorded history this release has come quite effectively from alcohol. It must have been discovered by accident, and probably in more than one place. It is readily
produced from any saccharous source, is pleasant tasting,
and not prone to any pathogenic divergence.
Whether alcohol appeared first from grapes as wine or
from grain as beer or from honey as mead is not known.
The catalyst that converts any of these into alcohol is ubiquitous. A recipe for beer has been found on a clay tablet
from Mesopotamia some 4000 yr old. It was probably
known during the new Stone Age, some 6000 yr ago. All
but three or four of the many cultures that have survived
to modern times knew alcohol. It is absent from polar people and Australian aborigines.
Probably the nature of the alcohol in any culture depended on the prevalence of the source. In cool northern
Europe it was likely to...
ALCOHOLIC
BEVERAGES
AND
HUMAN
RESPONSES
Alcoholic
beverages are,
in
essence,
flavored
solutions
of
ethanol.
The flavors may
come
from
grains,
as in
beer;
or
from
grapes
and
other
fruit,
as in
wine;
or
from
any
source
of
carbohydrates, grains, sugar,
or
grapes,
as in
whiskey,
rum,
and
brandy.
In
addition, consumers
may add
their
own
flavors, as
lime with some beers
or
fruits with some
wine
or
carbonated sodas with distilled
spirits.
The
spec-
trum
of flavors is
wide indeed.
But the
purpose
of
drinking
any
of
these
is to
supply ethanol
in
measured doses
to the
user.
Ethanol
is as
unique
as
humanity itself.
It is a
food
but
requires
no
digestion.
It
acts
on
many organs
in the
body
but
has no
cellular receptors
as do all
other drugs.
It is
stable
in the
atmosphere
to any
chemical change, whereas
all
other
foods
will undergo some kind
of
decomposition.
It
is the
only
food
produced solely
by
microbial action.
It en-
ters
any
cell
in the
body,
freely,
without
any
transport
mechanism.
All
other
foods
(and
all
other substances
ex-
cept
water) require
a
transport
mechanism
to
enter
any
cell.
It
provides energy more rapidly
than
any
other
food.
This article inquires more closely into these
and
other
aspects
of
ethanol. Although alcohol
is a
generic term
for
a
large group
of
related substances,
so
common
is
ethanol
that
the
term alcohol
has
been usurped
for it and
will
be
used
here
from
now on to
mean ethanol.
So
common
is the
drinking
of
alcoholic beverages
that
the
word drink
or
drinker implies
the
drinking
of
alcoholic beverages
and not
any
others.
People
have always needed
a
release
from
reality. From
earliest
recorded history
this
release
has
come quite
effec-
tively
from
alcohol.
It
must have been discovered
by
acci-
dent,
and
probably
in
more
than
one
place.
It is
readily
produced
from
any
saccharous
source,
is
pleasant tasting,
and not
prone
to any
pathogenic divergence.
Whether alcohol appeared
first
from
grapes
as
wine
or
from
grain
as
beer
or
from
honey
as
mead
is not
known.
The
catalyst
that
converts
any
of
these
into alcohol
is
ubiq-
uitous.
A
recipe
for
beer
has
been
found
on a
clay
tablet
from
Mesopotamia some 4000
yr
old.
It was
probably
known
during
the new
Stone Age, some 6000
yr
ago.
All
but
three
or
four
of the
many cultures
that
have survived
to
modern times knew alcohol.
It is
absent
from
polar peo-
ple
and
Australian aborigines.
Probably
the
nature
of the
alcohol
in any
culture
de-
pended
on the
prevalence
of the
source.
In
cool
northern
Europe
it was
likely
to be
beer
or
mead.
In the
Near
East
it may
have been beer
or
wine.
In the Far
East
it was
prob-
ably
beer.
In
early cultures
the
making
of
alcohol
was so
cherished
that
it
fell
under
the
domain
of the
priest
and
clergy.
Vestiges
of
this
still
remain
in
many monasteries
in
Europe.
GENERAL
METABOLISM
OF
ALCOHOL
The
first
step
in the
metabolism
of
alcohol
is a
dehydro-
genation
to
acetaldehyde.
HH HH
HC-C-OH
**
HC-C-O
HH H
This
is
mediated
by the
enzyme alcohol dehydrogenase,
with nicotine adenine dinucleotide
(NAD
+
) as
hydrogen
acceptor.
The
reaction
is
reversible,
and the
reverse reac-
tion
is the
last
step
in the
process
by
which alcohol
is
pro-
duced
by
yeast.
This reaction
is
followed
by the
oxidation
of the
alde-
hyde
to
acetate, brought about
by
another enzyme, alde-
hyde
dehydrogenase, again with
NAD
+
.
This reaction
has
never been reversed.
The
acetate
in
turn
joins with
coen-
zyme
A to
form
the
ever-present acetyl CoA. This
can
take
part
in the
citric acid cycle
and be
oxidized
to
CO
2
and
H
2
O.
This scheme
is
shown
in
Figure
1.
Alcohol
dehydrogenase (ADH) exists
in
about
20
forms,
each with
differing
activity toward ethanol
and to
other
alcohols.
These isozymes vary
in
concentration among
di-
verse ethnic groups,
no
doubt accounting
for
different
sen-
sitivities
to
alcohol
by
different
peoples.
All
forms
have zinc
as the
core metallic element.
ADH is
found
in all
tissues,
including
red and
white
blood
cells
and the
brain.
Before
1970,
it was
thought
that
ADH
existed only
in the
liver,
but
that
is
certainly
not the
case.
That
it is
present
in
many
isosteric
forms
is
probably rooted
in the
many
functions
it
performs
and the
many needs
it
satisfies
in
metabolism.
Aldehyde
dehydrogenase
(ALDH)
also exists widely
in
humans.
Cytoplasmic
ALDH
is the
same
in all
people,
whereas
the
mitochondrial
ALDH
does
differ
among peo-
ple,
with
that
found
in
Asians being less active
than
the
form
found
in
whites.
But it is
probable
that
mitochondrial
ALDH
is not
nearly
as
important
in
oxidizing acetaldehyde
as is
cytoplasmic ALDH. Because very
little
acetaldehyde
is
found
circulating
in the
blood even after high alcohol
intake,
it is
assumed
that
the
rate-limiting step
in
alcohol
metabolism
is the first
step—its
dehydrogenation
to
acet-
aldehyde.
HOW
ALCOHOL
IS
CONSUMED
Wine
The
fermentation
of the
juice
of
grapes produces
a
wine
containing about
12%
alcohol
by
volume (10%
by
weight).
The
stoichiometry
of
fermentation,
C
6
H
12
O
6
->
2C
2
H
5
OH
+
2CO
2
180 92 88
dictates
that
a
22°Brix grape juice will give
an
alcohol
so-
lution
of
somewhat more
than
10% by
weight. Perhaps
by
evolutionary coincidence,
a 10%
alcohol solution
is
close
to
the
limit
that
most yeasts
can
produce.
Because most countries
forbid
the
addition
of
water
to
grape juice
before
fermentation, wines worldwide
are
very
similar
in
alcohol content. Champagnes, which
are
fer-
mented twice,
may be a
little
higher,
say 14% by
volume.
Fortified
wines, such
as
port
and
sherry,
are
wines
to
which
brandy
has
been added
at
some
stage.
These
may
contain
as
much
as 20%
alcohol
by
volume.
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