Alcohol and the Human Body
from
Intoximeters
Incorporated
Alcohol's Properties1
Alcohol is a general term denoting a family of organic chemicals
with common properties. Members of this family include ethanol,
methanol, isopropanol, and others. This introduction discusses the
physical, chemical, and physiological aspects of the most commonly
ingested of these - ethanol.
Alcohol (ethanol) is a clear, volatile liquid that burns (oxidizes)
easily. It has a slight, characteristic odor and is very soluble
in water. Alcohol is an organic compound composed of carbon, oxygen,
and hydrogen; its chemical formula is C2H5OH.
Alcohol is a central nervous system depressant and it is the central
nervous system which is the bodily system that is most severely
affected by alcohol (see chart below). The degree to which the central
nervous system function is impaired is directly proportional to
the concentration of alcohol in the blood2.
When ingested, alcohol passes from the stomach into the small intestine,
where it is rapidly absorbed into the blood and distributed throughout
the body. Because it is distributed so quickly and thoroughly the
alcohol can affect the central nervous system even in small concentrations.
In low concentrations, alcohol reduces inhibitions. As blood alcohol
concentration increases, a person's response to stimuli decreases
markedly, speech becomes slurred, and he or she becomes unsteady
and has trouble walking. With very high concentrations - greater
than 0.35 grams/100 milliliters of blood (equivalent to 0.35 grams/210
liters of breath ) - a person can become comatose and die. The American
Medical Association has defined the blood alcohol concentration
level of impairment for all people to be 0.04 grams/100 milliliters
of blood (equivalent to .04 grams/210 liters of breath). The following
is a generally accepted guide to the effects of alcohol.
Stages of alcohol intoxication33
BAC
(g/100 ml of blood
or g/210 l of breath) |
Stage |
Clinical symptoms |
0.01 - 0.05 |
Subclinical |
Behavior nearly normal by ordinary observation |
0.03 - 0.12 |
Euphoria |
Mild euphoria, sociability, talkitiveness
Increased self-confidence; decreased inhibitions
Diminution of attention, judgment and control
Beginning of sensory-motor impairment
Loss of efficiency in finer performance tests |
0.09 - 0.25 |
Excitement |
Emotional instability; loss of critical judgment
Impairment of perception, memory and comprehension
Decreased sensitory response; increased reaction time
Reduced visual acuity; peripheral vision and glare recovery
Sensory-motor incoordination; impaired balance
Drowsiness |
0.18 - 0.30 |
Confusion |
Disorientation, mental confusion; dizziness
Exaggerated emotional states
Disturbances of vision and of perception of color, form,
motion and dimensions
Increased pain threshold
Increased muscular incoordination; staggering gait; slurred
speech
Apathy, lethargy |
0.25 - 0.40 |
Stupor |
General inertia; approaching loss of motor functions
Markedly decreased response to stimuli
Marked muscular incoordination; inability to stand or
walk
Vomiting; incontinence
Impaired consciousness; sleep or stupor |
0.35 - 0.50 |
Coma |
Complete unconsciousness
Depressed or abolished reflexes
Subnormal body temperature
Incontinence
Impairment of circulation and respiration
Possible death |
0.45 + |
Death |
Death from respiratory arrest |
Absorption4
Alcohol is absorbed from all parts of the gastrointestinal tract
largely by simple diffusion into the blood. However the small intestine
is by far the most efficient region of the gastrointestinal tract
for alcohol absorption because of its very large surface area. In
a fasting individual, it is generally agreed that 20% to 25% of
a dose of alcohol is absorbed from the stomach and 75% to 80% is
absorbed from the small intestine. Because of this peak blood alcohol
concentrations are achieved in fasting people within 0.5 to 2.0
hours, (average 0.75 - 1.35 hours depending upon dose and time of
last meal) while non-fasting people exhibit peak alcohol concentrations
within 1.0, and in extreme cases up to as much as 6.0 hours (average
1.06 - 2.12 hours).
Distribution
Alcohol has a high affinity for water and is therefore found in
body tissues and fluids inasmuch as they contain water. Absorbed
alcohol is rapidly carried throughout the body in the blood and
once absorption of alcohol is complete an equilibrium occurs such
that blood at all points in the system contains approximately the
same concentration of alcohol.
Elimination
The liver is responsible for the elimination - through metabolism
- of 95% of ingested alcohol from the body. The remainder of the
alcohol is eliminated through excretion of alcohol in breath, urine,
sweat, feces, milk and saliva. The body uses several different metabolic
pathways in its oxidation of alcohol to acetaldehyde to acetic acid
to carbon dioxide and water.
Healthy people metabolize alcohol at a fairly consistent rate.
As a rule of thumb, a person will eliminate one average drink or
.5 oz (15 ml) of alcohol per hour. Several factors influence this
rate. The rate of elimination tends to be higher when the blood
alcohol concentration in the body is very high or very low. Also
chronic alcoholics may (depending on liver health) metabolize alcohol
at a significantly higher rate than average. Finally, the body's
ability to metabolize alcohol quickly tend to diminish with age.
Body Weight and Body Type
In general, the less you weigh the more you will be affected by
a given amount of alcohol. As detailed above, alcohol has a high
affinity for water. Basically one's blood alcohol concentration
is a function of the total amount of alcohol in one's system divided
by total body water. So for two individuals with similar body compositions
and different weights, the larger individual will achieve lower
alcohol concentrations than the smaller one if ingesting the same
amount of alcohol.
However, for people of the same weight, a well muscled individual
will be less affected than someone with a higher percentage of fat
since fatty tissue does not contain very much water and will not
absorb very much alcohol.
Rate Of Consumption
Blood alcohol concentration depends on the amount of alcohol consumed
and the rate at which the user's body metabolizes alcohol. Because
the body metabolizes alcohol at a fairly constant rate (somewhat
more quickly at higher and lower alcohol concentrations), ingesting
alcohol at a rate higher than the rate of elimination results in
a cumulative effect and an increasing blood alcohol concentration.
Alcohol Content
It's not how many drinks that you have, but how much alcohol that
you consume. As you can see from the chart below some drinks are
more potent than others.
Alcohol Content of Some Typical Drinks5
Drink |
Alcohol Content |
Manhattan |
1.15 oz. (34 ml) |
Dry Martini |
1.00 oz. (30 ml) |
Malt liquor -12 oz. (355 ml) |
0.71 oz. (21 ml) |
Airline miniature |
0.70 oz. (21 ml) |
Whiskey Sour/Highball |
0.60 oz. (18 ml) |
Table Wine - 5 oz. (148 ml) |
0.55 oz. (16 ml) |
Beer - 12 oz. (355 ml) |
0.54 oz. (16 ml) |
Reduced Alcohol Beer |
0.28 oz. (8 ml) |
Mixed drinks are based on typical drink recipes using
80 proof liquor.
The amount of alcohol in actual mixed drinks may vary.
Alcohol Content (in Percent) of Selected Beverages6
Beverage |
Alcohol Content (%) |
Beers (lager) |
3.2 - 4.0 |
Ales |
4.5 |
Porter |
6.0 |
Stout |
6.0 - 8.0 |
Malt Liquor |
3.2 - 7.0 |
Sake |
14.0 - 16.0 |
Table wines |
7.1 - 14.0 |
Sparkling wines |
8.0 - 14.0 |
Fortified wines |
14.0 - 24.0 |
Aromatized wines |
15.5 - 20.0 |
Brandies |
40.0 - 43.0 |
Whiskies |
40.0 - 75.0 |
Vodkas |
40.0 - 50.0 |
Gin |
40.0 - 48.5 |
Rum |
40.0 - 95.0 |
Aquavit |
35.0 - 45.0 |
Okolehao |
40.0 |
Tequila |
45.0 - 50.5 |
The concentration of the drinks that one ingest can have a slight
effect on the peak alcohol concentration due to the differences
in absorption rate of different concentrations of alcohol. Alcohol
is most rapidly absorbed when the concentration of the drink is
between 10% and 30%. Below 10% the concentration gradient in the
gastrointestinal tract is low and slows absorption and the added
volumes of liquid involved slow gastric emptying. On the other hand
concentrations higher than 30% tend to irritate the mucous membranes
of the gastrointestinal tract and the pyloric sphincter, causing
increased secretion of mucous and delayed gastric emptying.
Food
Food taken along with alcohol results in a lower, delayed blood
alcohol concentration peak (the point of greatest intoxication).
There are two major factors involved in this phenomenon.
First, because alcohol is absorbed most efficiently in the small
intestine, the ingestion of food can slow down the absorption of
alcohol into one's system. The pyloric valve at the bottom of the
stomach will close in order to hold food in the stomach for digestion
and thus keep the alcohol from reaching the small intestine. While
alcohol will be absorbed from the stomach it is a slower and less
efficient transition.
Second and equally important is the fact that alcohol elimination
rates are inversely proportional to alcohol concentration in the
blood. Therefore the suppressed levels of alcohol due to food ingestion
cause the body to eliminate the alcohol that is absorbed at a faster
rate.
The type of food ingested (carbohydrate, fat, protein) has not
been shown to have a measurable influence on this affect but the
larger the meal and closer in time between eating and drinking,
the greater the diminution of peak alcohol concentration. Studies
have shown reductions in peak alcohol concentration (as opposed
to those of a fasting individual under otherwise similar circumstances)
of 9% to 23%.
Medication
If you are taking any medication, it could increase the effects
of alcohol. You should always consult your physician or the medical
information that accompanies the medication when drinking alcohol
in conjunction with any medication.
Fatigue
Fatigue causes many of the same symptoms that are caused by alcohol
intoxication. These and other symptoms will be amplified if alcohol
intoxication is concurrent with fatigue.
Tolerance
Tolerance is the diminution of the effectiveness of a drug after
a period of prolonged or heavy use of that drug or a related drug
(cross-tolerance). There are two types of tolerance at work with
alcohol. The first is metabolic tolerance in which the alcohol
is metabolized at a higher rate (up to 72% more quickly) in chronic
users. Because of the higher metabolic rate for alcohol lower peak
blood alcohol concentrations are achieved by chronic alcohol users
than the average drinker when the same amount of alcohol is ingested.
The second is functional tolerance in which there is an actual
change in the organ or system's sensitivity to the drug. Studies
have shown that chronic alcohol users can have twice the tolerance
for alcohol as an average person. It is important to note however
that even in light of these tolerance factors, it has been shown
conclusively that even in heavy alcohol users functional impairment
is clearly measurable at the blood alcohol concentration levels
that are currently used for traffic law enforcement and safety sensitive
job performance.
Gender Differences
As outlined above in the section on Body Weight
and Body Type different body types coincide with different body
water percentages. In general, but by no means in all cases, women
tend to have a higher percentage of body fat and thus a lower percentage
of body water. Therefore, in general, if a man and a woman of the
same weight ingest the same amount of alcohol the woman will tend
to achieve a higher alcohol concentration. This, of course, would
not be true if the woman was very fit and the man was somewhat obese,
but on average, this is the case. Furthermore, total body water
tends to decrease with age, so an older person will also be more
affected by the same amount of alcohol. According to the table below
the differences in alcohol concentration due to average body composition
differences based on gender would be between 16% and 10% depending
on age.
Average Total Body Water
as a function of Sex and Age
Age |
Male |
Female |
18 to 40 |
61% |
52% |
over 60 |
51% |
46% |
Another gender based difference is in the elimination of alcohol.
Although not explained, studies appear to show that women eliminate
alcohol from their bodies at a rate 10% greater than that of men.
|