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 of alcohol.
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


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