Alcohol's Effect on the Body

views updated

Chapter 2
Alcohol's Effect on the Body

Perhaps because beer, wine, and other alcoholic beverages are so common in everyday life, most people do not think of alcohol as a drug. But alcohol is a drug, a powerful central nervous system depressant that is generally classified with similar drugs such as barbiturates, minor tranquilizers, and general anesthetics. As a depressant, alcohol depresses, or slows down, the operation of the central nervous system, which includes the brain and the spinal cord.

The depressed performance of the central nervous system caused by alcohol consumption creates the slurred speech, impaired physical coordination, and other physical signs that indicate a person has been drinking. But in Under the Influence: A Guide to the Myths and Realities of Alcoholism, authors James R. Milam and Katherine Ketcham explain that this drug is complex in the variety of ways it can affect the human body: "Alcohol is an infinitely confusing substance. In small amounts it is an exhilarating stimulant. In larger amounts it acts as a sedative and as a toxin, or poisonous, agent."17

Thus, when people first begin drinking, they usually feel happy and more energetic. As they consume more and more alcohol, however, the drug's depressive effects begin to emerge, creating the behavior associated with being intoxicated. Finally, if a person consumes enough alcohol at one time, this drug can be deadly. And all of these complex reactions to alcohol begin in one place––the brain.

Alcohol and the Brain

Alcohol is easily and quickly absorbed into the body. This process begins before the drinker even swallows a sip of beer or wine because 5 to 10 percent of alcohol is transferred to the bloodstream directly through the lining of the mouth. The beverage then passes through the stomach and small intestine, where a high concentration of small blood vessels speeds absorption into the bloodstream. As alcohol moves into the bloodstream, it spreads throughout the body. However, its effect on the brain is almost immediate. There are two reasons for this: a substantial portion of the blood that the heart pumps goes directly to the brain, and the brain's fatty material readily and easily absorbs alcohol.

People have understood for thousands of years that drinking beer, wine, and liquor makes them intoxicated, but it was not until the last two decades of the twentieth century that scientists discovered how alcohol actually does this. As late as 1974 the National Institutes of Health (NIH) issued a report saying, "No one knows how alcohol intoxicates [people]."18 But by 2000, in its Tenth Special Report to the U.S. Congress on Alcohol and Health, researchers for the NIH and its National Institute on Alcohol Abuse and Alcoholism (NIAAA) finally had the answer: "The changes in behavior seen soon after consumption of alcohol––as well as the euphoria and anxiety reductions seen with alcohol––all result from alcohol's actions on the brain."19

How Blood Alcohol Levels Rise

How intoxicated people become when they drink depends on how fast their liver can process alcohol. A normal, healthy liver can break down and eliminate 0.5 ounces of pure alcohol from the bloodstream each hour, which is the equivalent of 12 ounces of beer, 5 ounces of table wine, or 1.5 ounces of 80-proof distilled spirits. When people drink more than those amounts in an hour, their blood alcohol levels (BALs) will go up; if the levels rise high enough, they will become drunk. The following is an example of how this happens, taken from Beyond the Influence: Understanding and Defeating Alcoholism.

It's a Sunday evening in Denver, the Broncos have just won the Super Bowl, and Joe is in a party mood. Around 8 p.m. he joins some friends at a local tavern, and in the next four hours he downs twelve beers and four shots of 80-proof tequila. In all the excitement, Joe, who weighs 165 pounds, forgets to eat dinner, munching on pretzels and potato chips instead. By midnight, when Joe falls into bed, his liver has burned up 2 ounces of pure alcohol (about four beers). By 6:00 a.m., when he wakes up, his liver has eliminated an additional 3 ounces (six more beers). On his way to work at 7:00 a.m., Joe still has approximately 2 ounces of pure alcohol circulating around in his bloodstream (the remaining beers and 4 ounces of tequila). Seven hours after Joe stopped drinking, he is still legally drunk. Unfortunately for Joe, there's nothing he can do to nudge his liver along and accelerate the metabolic process. Coffee, cold showers, fruit juice, and exercise are all basically useless, for the fact remains that if you drink more than your liver can process at one time, your [BAL] will rise. If you keep drinking, you'll get drunk. And the more you drink, the drunker you'll get.

The brain and spinal cord make up the central nervous system, which controls physical behavior like walking as well as involuntary actions necessary for life, such as breathing and the beating of the heart. The central nervous system runs along the spinal cord and branches out into every part of the body. The brain is in continuous direct communication with all of these parts, sending messages through this system to control its actions. These directives, which are in effect commands to various muscles and parts of the body, pass between individual cells via what are called neurotransmitters.

The latest research on drinking shows that alcohol interferes with this flow of commands from the brain at the level of the neurotransmitters, and that this disruption of communication from the brain is the major change that causes intoxication. Thus, intoxication is caused by alcohol working directly on the brain to dull or hamper the way it works.

Intoxication is a gradual process; it does not occur after a person has consumed one drink but several. This is because alcohol in the bloodstream has to build to sufficient levels to start affecting how the brain operates.

Alcohol Levels

Alcohol is processed in the body through a series of chemical reactions. These reactions—called metabolism—break down food and other ingested substances to simple compounds the body can use. The liver is the organ that does the bulk of this work. It metabolizes alcohol, removing

[Image not available for copyright reasons]

it from the bloodstream at a constant rate of one standard drink per hour. A standard drink is defined as 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits, all of which contain .5 ounces of alcohol. Because the human body can only process alcohol at that fixed rate of one drink per hour, people who consume more than one drink per hour will gradually increase the alcohol levels in their blood. The result of this is that they will become intoxicated.

The body's blood alcohol concentration (BAC), also known as blood alcohol level (BAL), is the medically recognized method for calculating how much someone has had to drink. The BAC is the amount of alcohol in the blood measured in percentages; a BAC of 0.10 percent, for example, means that a person's bloodstream has one part alcohol per one thousand parts of blood.

As alcohol levels rise, intoxication begins. The effects of intoxication are many and varied, and they continually change as people keep drinking.


The types of behavior that begin occurring soon after people start drinking alcohol are collectively referred to as intoxication. This state includes impaired physical coordination and mental performance as well as changes in a person's emotions, including a feeling of relaxation and a lessening of fear or anxiety over personal problems. Although for most people these initial sensations are usually pleasant, the effects of alcohol intensify as drinkers consume more alcohol. This leads to difficulty in how a person reacts and responds physically, mentally, and emotionally to what is happening around him or her.

The way alcohol affects people is complex, however, and the effects it creates change as people drink more and more. Although alcohol is a depressant, it acts more like a stimulant when people first take a drink. Moderate doses of alcohol increase blood flow, accelerate the heart rate, and stimulate brain cells to speed the transmission of nerve impulses. In Beyond the Influence: Understanding and Defeating Alcoholism, Katherine Ketcham and William F. Asbury explain that these physiological changes in turn create a feeling of emotional well-being, which is the main reason that people enjoy drinking:

We turn to alcohol for relaxation and stress reduction, and the drug delivers almost immediately by making us feel happy, energetic, and at peace with ourselves. These pleasurable, tension-relieving sensations are due to alcohol's stimulating effects on the body, particularly the brain and the heart.20

In an average person, one standard drink will produce a light feeling of pleasantness or exhilaration. People who consume two glasses of wine or bottles of beer will tend to have a heightened feeling of relaxation coupled with a decrease in fine motor skills, and those who have three drinks will begin to have slower physical reaction times, decreased muscular control, and slurred speech. Even at this stage, many people will still be able to function almost normally physically and mentally, although some drinkers, especially those who do not drink often, may begin to experience some problems.

However, the more people drink the more intoxicated they will become. And as the level of alcohol in their system rises, alcohol will begin creating new and quite different physical and mental reactions.


Because the initial sensations of intoxication are so enjoyable, most people continue drinking alcohol in an attempt to heighten them.

Blood Alcohol Level and Intoxication

The amount of alcohol in a person's bloodstream is referred to as blood alcohol level (BAL) or blood alcohol concentration (BAC). It is recorded in milligrams of alcohol per 100 milliliters of blood; a BAC of 0.10 means that 1/10 of 1 percent of total blood content is alcohol. A reading of 0.10 percent is considered legal proof that a person is drunk in most states. The following are some examples of the observable effects of certain BALs on occasional social drinkers (because of their higher tolerance, an alcoholic or problem drinker must have BALs several times higher before alcohol will create the same effects in them).

At 0.03 to 0.05 percent, a flushed face, feeling of euphoria, and increased social confidence; at 0.50 to 0.15 percent, disturbed thinking and coordination, reduced self-control, irresponsible talk and behavior; at 0.15 to 0.25 percent, confused thinking, unsteady gait, slurred speech; at 0.25 to 0.40 percent, extreme confusion and disorientation, difficulty remaining upright, drowsiness, risk of falling into a coma (a state of deep unconsciousness from which the person cannot be aroused); 0.40 to 0.50 percent, risk of death due to cessation of breathing (although habitual drinkers may survive even such high levels).

The problem is that as people consume more alcohol, it begins to act like the type of drug it really is—a depressant—and it has a sedative effect. Rising levels of alcohol in a person's bloodstream begin to slow nerve and brain activity and at very high levels will make a person unconscious as surely as a sleeping pill.

[Image not available for copyright reasons]

When people are in this heightened stage of intoxication, they are commonly said to be drunk. It is alcohol's depressant power that creates the physical changes most people associate with someone who is drunk, such as inarticulate or slurred speech, out-of-focus eyes, and jerky, out-of-synch physical movements, including a staggering walk. These effects are opposite from those produced initially by small doses of alcohol, when the drug had a mildly stimulating effect on the drinker.

The severity of intoxication or drunkenness is linked directly to how much alcohol a person has in his or her bloodstream. As blood alcohol concentrations continue to increase, drinkers will have more and more trouble performing everyday tasks such as walking and talking, and even their vision will eventually become blurred.

At BACs higher than 0.30 percent, the drinker will be in a semistupor and can pass out, falling asleep for a short time or even several hours. When BACs reach 0.50 percent, a person can fall into a deep coma and will be in danger of dying. At even higher levels, alcohol works as a poison. It can kill by depressing the intoxicated person's brain activity so much that the drinker will stop breathing. This form of death is known as "alcohol poisoning."

The physical effects of alcohol are the most noticeable and the easiest to understand. However, the changes that take place in a drinker's mental and emotional states are just as dramatic.

Intoxicated Behavior

Just as alcohol can impair a drinker's physical behavior, it can also diminish the ability to reason and think clearly. Drinkers who become intoxicated discover that it becomes harder to remember things, to concentrate on what they are doing or saying, to understand what is happening to them and to others around them, and to make judgments concerning situations in which they are involved. An intoxicated person's ability to think and reason can become as garbled and disjointed as his or her attempts to speak. Harry Milt, author of Alcoholism, Its Causes and Cure: A New Handbook, explains that this impairment is one that sneaks up on people as they keep drinking:

With the first drink or two an illusion may be created of clarity of mind and thought [but] as the alcohol continues to bathe the brain, consciousness becomes blurred, thinking is slowed down, the content of thought is [reduced], memory is blurred. Concepts are poorly formulated, reasoning is foggy, judgment is blunted.21

Talking to someone who is intoxicated often seems like conversing with a child. People who are drunk often fail to understand what someone is telling them, keep interrupting to say something unrelated to what the other person is saying, and usually have trouble listening for very long because they are easily distracted. Drunk people act very much as if their intelligence has been diminished—which it is, temporarily—because their brains are not functioning correctly.

In addition to the problems intoxicated drinkers have in knowing and understanding what is going on around them intellectually, changes also take place in their emotional state. Most people feel happy when they have their first few drinks. As they drink more and more, however, their emotions change, often in a volatile way as they experience radical swings between moods as varied as joy, sadness, happiness, and anger. Increased consumption can also bring out negative personality characteristics such as aggressiveness and cruelty.

How Alcohol Acts on the Brain

Scientists now understand that people become intoxicated by the way alcohol affects their brain's ability to control the body. This process is very complex, but in its Tenth Special Report to the U.S. Congress on Alcohol and Health, which summarizes the latest research on alcohol and how it affects people, the NIH and NIAAA provide a simplified explanation of how this happens.

The brain communicates through neurons, nerve cells that are specialized to receive and rapidly conduct chemical and electrical signals. Electrical signals help fulfill the neuron's major role—to communicate information quickly to the rest of the body so that the brain can carry out its many functions. Neurotransmitters in each cell enable these signals to travel from the brain to all parts of the body. The Tenth Special Report states, "Alcohol appears to affect the function of several neurotransmitters by altering the communication mechanism between neurons. A large body of evidence suggests that this effect of alcohol on transmission [of signals from the brain] is the major change in the brain that gives rise to intoxication." In simple terms, this means that alcohol works on the cellular level to disrupt communication from the brain, resulting in the physical, mental, and emotional behaviors associated with intoxication.

One of the main effects of alcohol, as well as one of its most damaging, is to lessen people's inhibitions, making it easier for them to surrender to negative impulses or emotions they normally would resist. Sociologist Sherri Cavan writes that alcohol makes drinkers feel that "the constraint and respect the social world ordinarily requires [of their behavior] is no longer demanded [of them]."22 For example, when intoxicated drinkers become angry at someone, they often lash out physically at that person even though they would not do so if they were sober.

As with the physical effects of intoxication, the mental and emotional changes that take place continue to intensify as people consume more alcohol. The severity of this intoxication can be correlated directly to the drinker's blood alcohol levels; the higher the BAC, the drunker the person will be.

However, the degree of intoxication from drinking the same amount of alcohol will vary among individuals and even in the same individual at different times. That is because several important factors influence how rapidly alcohol will make someone intoxicated.

[Image not available for copyright reasons]

Factors in Becoming Intoxicated

Because of the way alcohol circulates in the body, a person's size plays an important part in determining how quickly alcohol will affect him or her and how drunk that person will become. A person weighing 220 pounds, for instance, will not become as intoxicated by the same number of drinks as a person weighing 120 pounds. Because the blood supply is correspondingly bigger, a similar amount of alcohol will be more diluted in the larger person's body. Another consideration is whether the drinker has eaten lately. The presence of food in a person's stomach will slow down how quickly alcohol is absorbed into the bloodstream.

There are also individual variances in the speed with which people metabolize alcohol because of their own unique body chemistry. The gender of the drinker makes a difference because women usually absorb and metabolize alcohol more quickly than men, which means they will have higher BACs after consuming the same amount of alcohol.

A key factor is whether the person having a drink is a regular drinker. Dr. Gail Gleason Milgram explains that experience with alcohol plays a part in how intoxicated people will become by consuming the same amount of alcohol:

Someone drinking a glass of wine [for the first time] may experience lightheadedness but will probably not experience that effect on subsequent occasions. However, most individuals who drink know what to expect from various amounts of alcohol because of their prior experience with drinking.23

The reason for this is that when people drink on a regular basis, their bodies build up a physical tolerance to alcohol that helps them stay sober. Regular drinkers also become so accustomed to what alcohol does to their bodies that they can better cope with the changes alcohol causes.

Health Dangers

Although alcohol's effects are powerful, there are not many immediate health risks from occasional drinking. For those who do drink too much, the most common health problem is a hangover, the symptoms of which include headaches, nausea, and other bodily discomfort. A hangover can last for hours or even days depending on how much the person drank.

Occasional drinkers must also be careful to make sure they are not taking any medication that could interact with the alcohol they are consuming. In some cases, alcohol can react with prescription drugs to make a person very ill.

A Dangerous Drug

Although there are not many health risks for those who drink moderately once in a while, alcohol in large amounts is both powerful and potentially dangerous. Many serious health consequences exist for people who drink a lot over a long period, including liver and brain damage.

Alcohol is also highly addictive, and when a person becomes hooked on drinking, this drug can destroy his or her life. In The Facts About Drugs and Alcohol, Dr. Mark S. Gold explains just how dangerous this drug can be. "Alcohol," he writes," is the most destructive drug known to mankind . . . without a doubt, the world's most abused substance."24

About this article

Alcohol's Effect on the Body

Updated About content Print Article