Physiology of Alcohol
Alcohol is not digested like other foods. Instead of being converted
and transported to cells and tissues, it avoids the normal digestive
process and goes directly to the blood stream. About 20 percent
of the alcohol is absorbed directly into the bloodstream from the
stomach walls and 80 percent is absorbed into the bloodstream through
the small intestine.
Until all alcohol consumed has been metabolised, it is distributed
throughout the body. Alcohol is highly soluble in water and tends
to distribute itself in the water tissues of the body. Hence organs
containing lots of water and needs ample blood supply, like the
brain, are particularly vulnerable to the effects of alcohol.
Metabolism / Elimination
The body processes and eliminates alcohol through metabolism. About
90% of alcohol is metabolised through the liver. The other 10% is
excreted from the body through exhalation and urine.
In general, the amount of blood alcohol peaks within 30 to 45 minutes
after consumption of one drink. The average person metabolises about
1 standard drink (10 grams) per hour.
Factors affecting Metabolism and Effect of Alcohol
The effects of alcohol vary from person to person. Different people
consuming the same amount of alcohol may react differently and the
same person can have different reactions on different occasions.
The following are major factors affecting the metabolism of alcohol
and the variation in signs and symptoms:
The strength of the drink - In general, higher concentrations
of alcohol result in more rapid absorption. Pure alcohol is generally
absorbed faster than diluted alcohols, which are, in turn, absorbed
faster than wine or beer. However, alcohol taken in concentrated
amounts can irritate the stomach to the extent that it delays absorption
there as well as delays the passing of alcohol to the small intestine,
further delaying the absorption into bloodstream.
Speed of Drinking - The more rapidly the beverage is ingested,
the higher the peak blood alcohol concentration (BAC). The liver
metabolises about 10 grams of alcohol per hour.
Food - the longer the alcohol remains in the stomach, the
slower it will be absorbed and the lower will be the peak in the
blood alcohol concentration (known as BAC). This explains why eating
while drinking slows down the absorption rate. When alcohol is taken
with food, absorption generally is complete in 1-3 hours during
which time the BAC will peak. When alcoholic beverages are taken
with a substantial meal, peak BAC may be reduced by as much as 50%.
Body Weight - The more mass and fluid in the body, the more
diluted the alcohol in the body will be and requires greater amounts
of alcohol to reach a given BAC. Two people may weigh the same,
yet their bodies may have different proportions of tissue containing
water and fat. Consider a tall, thin person and a short, fat person
of the same weight. The short, fat person will have more fat and
less water making up his body than the tall, thin person. The fat
person will reach a higher BAC than the thin person when both drink
the same amount of alcohol.
Gender - Muscle tissue contains more water than fat tissue.
On average, men have more muscle and less fat than women, and can
have about 10 percent more water in their bodies. As alcohol dilutes
itself in water, females will reach a higher BAC than their male
counterparts of the same weight when both drink the same amount
Females are generally more affected by alcohol just prior to menstruation.
Females taking birth control pills or medications containing estrogen
may remain intoxicated longer than those who do not, due to the
liver's function of metabolizing both.
Drinking History - As a person's drinking increases, his
or her liver will increase its capacity to metabolise alcohol. Hence,
a heavy drinker will be able to burn off drinks much faster.
Taking drugs - The effects of alcohol may be enhanced if
the person is taking certain drugs, especially those of the sedative
class such as sleeping pills or anti-anxiety medications. Prescription,
over-the-counter, illicit and unrecognised drugs all have potential
reactions with alcohol. Alcohol together with drug could be lethal.
A person who is not habituated to either alcohol or sedatives may
cause serious harm, or death, in taking sub-lethal doses of each.
Emotional and Medical Conditions - The presence of a wide
variety of medical conditions may affect someone alcohol tolerance.
For example, many people seem more susceptible to the effects of
alcohol when they are fatigued, have recently been ill, or are under
emotional stress and strain. The usual amount of alcohol may result
in uncomfortable effects