The stomach has an enzyme which processes ethanol into a safer substance. The enzyme is called alcohol dehydrogenase. Heavy drinkers and people with alcohol problems tend to have severely reduced levels of this important enzyme

When an individual consumes alcohol, about 20% of the alcohol is absorbed in the stomach and 80% is absorbed in the small intestine.

The longer the stomach has to work on the ethanol, two effects may occur… enzymes will work on some of it, and the speed at which the body absorbs it will be slowed.  When a meal is eaten the exit valve of the stomach closes in order to digest the food. When food and alcohol are consumed at the same time this prevents the alcohol from passing quickly into the small intestine from where it would be rapidly absorbed giving dehydrogenase more time to work.

In general, the less an individual weighs the more they will be affected by a given amount of alcohol. Alcohol has a high affinity for water. An individual who is well muscled will be less affected than someone with a higher percentage of body fat since fatty tissue contains less water.

Alcohol is a strong poison. When alcohol enters the body, many organs go to work to expel it from the body as quickly as possible. Once absorbed by the stomach or small intestine, alcohol circulates in the bloodstream until it is processed by to the liver or lost through the urine, breath, or skin. The Liver is the main organ that rids the body of alcohol by breaking it down. It metabolizes about 90% of the alcohol in our body while about 10% is processed by the kidneys, lungs, and skin, and excreted through either the urine, breath, or skin surface.

The liver completes the breakdown of alcohol. The liver metabolizes about 90% of the alcohol in the body while about 10% is excreted through urine, the breath or skin.

The liver produces toxins in the body as a by-product of breaking down alcohol. When the liver is metabolizing alcohol it produces acetaldehyde, a substance which has toxic effects on the liver, brain and stomach lining, resulting in headache, nausea, vomiting and heartburn (also known as a hangover).

After entering the blood stream, alcohol quickly travels to all organs of the body, including the brain. In the brain, alcohol can impair the faculties, creating difficulty walking, blurred vision, slurred speech, slowed reaction times, very poor judgment, and memory impairment. These impairments can begin after only a small amount of alcohol, perhaps after only one or two drinks, at BAC levels and as low as .02.

In social drinkers impairment disappears as the individual sobers up. In chronic drinkers these symptoms can become long term.

Factors influencing the degree to which the brain is affected by alcohol:
• How much and how frequently an individual drinks
• The age at which drinking begins and how many years it continues
• Age, gender, genetic background, and family history
• General health status.

At relatively low levels (less than .07 BAC) alcohol stimulates electrical activity in the brain affecting pleasure and euphoria. It also works on the circuits targeted by drugs like Valium - calming, easing anxiety, and acting as a relaxant. Alcohol also acts on the serotonin system, which like Prozac, can increase self-confidence and reduce depression.

In larger quantities (over .08 BAC) alcohol interferes with chemical messages in the brain. It can make the drinker clumsy, with poor coordination and slurred speech. It dramatically reduces the ability to learn and form memories. Regular drinking sessions can make it very difficult to learn new skills or retain new knowledge.

After years of heavy drinking, adults with alcoholism show smaller brain sizes and run the risk of developing serious and permanent changes in the brain. Wernicke–Korsakoff Syndrome is a degenerative brain disorder usually found in poorly nourished chronic alcoholics. It results in severe mental confusion, paralysis of the nerves that move the eyes and difficulty with muscle coordination. Sufferers may be too confused to find their way out of a room and may not be able to walk. This chronic and debilitating syndrome is also characterized by persistent learning and memory problems. Victims are forgetful, quickly frustrated, have long term memory recall problems and have difficulty with new memory formation.

Blackouts are among the most dangerous of all alcohol related effects.

Alcohol is well known to interfere with the hippocanthus, the part of the brain responsible for memory formation. Heavy drinking hinders the development of new long-term memories and frequently causes fragmentary or total memory loss of events during periods of rapid drinking (binge drinking). These effects are referred to as "blackouts". Blackouts can last anywhere from several minutes to several hours.

These episodes are not to be confused with "passing out", where the subject loses consciousness. In a blackout, it is only the memory of events during the period of alcohol intoxication that are lost. Memory loss can include everything up to and including acts of violence, vandalism, sexual intercourse and driving.

Blackouts can affect alcoholics, heavy drinkers as well as social and college drinkers. Blackouts occur with greater frequency over .25 BAC. The more rapidly one drinks the higher the likelihood of blacking out.

In a survey of 772 undergraduates (Wechsler et al. 2002), 40% of the students who had consumed alcohol reported experiencing at least one blackout in the preceding twelve months. 9.4% of these drinkers who reported drinking in the previous two weeks also reported having blackouts.

General hangover symptoms include headache, feeling sick or depressed, general irritation and discomfort. These after-effects can represent a danger in the workplace as great as that of an individual who is intoxicated.

Aside from the alcohol, drinks have small amounts of additives (congeners) that give drinks their color, flavor and smell. Congeners affect individuals differently and may contribute to feeling ill.

The pounding headache is caused by dehydration. Alcohol's toxicity can cause acids to accumulate in the stomach and intestines resulting in queasiness and nausea. The stomach lining becomes inflamed (gastritis) delaying digestion.

Alcohol can inflame the esophagus, the tube that carries food from the throat to the stomach, giving you heartburn.

When an individual consumes alcohol, often glucose consumption also increases. The Pancreas responds to this by producing more insulin, which removes the glucose. Once the process has started, the insulin carries on working removing glucose from the blood. Low blood glucose levels are responsible for the shakes, excess sweating, dizziness, blurred vision and tiredness.

Alcohol lowers people's inhibitions and often means that aggressive people become more aggressive when drunk.

Because it lowers inhibitions and affects judgment, alcohol can also trigger violent and confrontational behavior in normally calm people. People who have consumed alcohol are more likely to become victims of violence and sexual assault.

It can be dangerous if alcohol is mixed with prescriptions, and certain over the counter medications. Alcohol mixed with drugs can often compounds the effects making the symptoms more pronounced. Medication that causes sedation can be very dangerous when combined with alcohol. This mixture may cause difficulty breathing and compound the effects on an individual's ability to clearly think.

The following drugs should not be taken with alcohol. Always consult your physician before combing alcohol with any other medication.
• Barbiturates
• Benzodiazepines, such as Valium or Halcion.
• Codeine
• Anti-histamines
• Some painkillers
• Anti-depressants, such as Prozac.

Just as with prescription and over-the-counter medications, drinking alcohol and taking drugs like tranquillizers (valium), amphetamines (speed), antidepressants (prozac) or marijuana (cannabis, pot or weed) increase the effects.