Alcohol in the Body
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
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 affects of alcohol.
ml of bloodor g/210 l of breath)
|0.01 - 0.05
nearly normal by ordinary observation
|0.03 - 0.12
sociability, talkitivenessIncreased self-confidence;
decreased inhibitionsDiminution of attention,
judgment and controlBeginning of sensory-motor
impairmentLoss of efficiency in finer
|0.09 - 0.25
instability; loss of critical judgmentImpairment
of perception, memory and comprehensionDecreased
sensitory response; increased reaction
timeReduced visual acuity; peripheral
vision and glare recoverySensory-motor
incoordination; impaired balanceDrowsiness
|0.18 - 0.30
mental confusion; dizzinessExaggerated
emotional statesDisturbances of vision
and of perception of color, form, motion
and dimensionsIncreased pain thresholdIncreased
muscular incoordination; staggering gait;
slurred speechApathy, lethargy
|0.25 - 0.40
inertia; approaching loss of motor functionsMarkedly
decreased response to stimuliMarked muscular
incoordination; inability to stand or
walkVomiting; incontinenceImpaired consciousness;
sleep or stupor
|0.35 - 0.50
unconsciousnessDepressed or abolished
reflexesSubnormal body temperatureIncontinence
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,
while non-fasting people exhibit peak alcohol concentrations within 1.0 to
as much as 6.0 hours.
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.
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
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
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.
of Some Typical Drinks
liquor -12 oz. (355 ml)
Wine - 5 oz. (148 ml)
- 12 oz. (355 ml)
drinks are based on typical drink recipes
using 80 proof liquor.
The amount of alcohol in actual mixed drinks may vary.
(in Percent) of Selected Beverages
||Alcohol Content (%)
||3.2 - 4.0
||6.0 - 8.0
||3.2 - 7.0
||14.0 - 16.0
||7.1 - 14.0
||8.0 - 14.0
||14.0 - 24.0
||15.5 - 20.0
||40.0 - 43.0
||40.0 - 75.0
||40.0 - 50.0
||40.0 - 48.5
||40.0 - 95.0
||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 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%.
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 causes many of the same symptoms that are caused by alcohol intoxication.
These and other symptoms will be amplified if alcohol intoxication is concurrent
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.
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.
Body Water as a function of Sex and Age
|18 to 40