Biological Impacts Of Alcohol Use:
An Overview

By:  Michaele P. Dunlap, Psy.D,  Clinical Psychologist


Ethyl alcohol or ethanol, known commonly as alcohol, is the same whether the beverage is wine, beer, or hard liquor. Beverage alcohol is a drug that depresses the central nervous system, like barbiturates, sedatives, and anesthetics. Alcohol is not a stimulant. There is no question that the person who drinks alcohol seems stimulated. Speech becomes free and animated, social inhibitions may be forgotten, and the drinker can begin to act and feel more emotional. But these effects are misleading; the "stimulation" occurs only because alcohol affects those portions of the brain that control judgment. "Being stimulated" by alcohol actually amounts to a depression of self-control. A principal effect of alcohol is to slow down brain activity, and depending on what, how much, and how fast a person drinks, the result is slurred speech, hazy thinking, slowed reaction time, dulled hearing, impaired vision, weakened muscles and fogged memory. Certainly not a stimulating experience!

Alcohol is also classified as a food because it contains calories. The average drink has about the same calorie count as a large potato but, unlike a potato or any other food, alcohol has no nutritional value. The calories are empty.


Basics of alcohol metabolism:

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 blood through the stomach walls and 80 percent is absorbed into the bloodstream through the small intestine.

Alcohol dilutes itself in the water volume of the body in order to travel through the system. Those vital organs, like the brain, that contain a lot of water and need an ample blood supply are particularly vulnerable to the effects of alcohol. Alcohol's dilution in the body does cut its effect somewhat. There one important biological difference between men and women comes into play: Muscle tissue contains more water than fat tissue, so men -- who have more muscle and less fat on the average than women -- can have about 10 percent more water in their bodies. If a lean man and a lean woman of equal weight consume the same amount of liquor, the woman is more adversely affected for this and other reasons.

The initial impact of alcohol:

The brain, liver, heart, pancreas, lungs, kidneys, and every other organ and tissue system are infiltrated by alcohol within minutes after it passes into the blood stream. The strength of the drink will have a significant effect on absorption rates, with higher concentrations of alcohol resulting in more rapid absorption. Pure alcohol is generally absorbed faster than diluted alcohols, which are, in turn, absorbed faster than wine or beer.

Alcohol taken in concentrated amounts can irritate the stomach lining to the extent that it produces a sticky mucous which delays absorption. The pylorus valve which connects the stomach and small intestine may go into spasm in the presence of concentrated alcohol, trapping the alcohol in the stomach instead of passing it on to the small intestine where it would be more rapidly absorbed into the blood stream. The drinker who downs several straight shots in an effort to get a quick high may actually experience a delayed effect. Finally, the temperature of the beverage affects its absorption, with warm alcohol being absorbed more rapidly than cold alcohol.

Measurement of effect by blood alcohol level (BAL):

The drinker's blood alcohol level rises as a factor of the relationship among the amount of alcohol consumed, body size and proportion of body fat, the amount of food in the stomach, and what is mixed with the alcohol. The BAL rises more rapidly in those who drink on an empty stomach. Water and fruit juices slow the absorption process, while carbon dioxide speeds it up. The carbon dioxide in champagne and carbonated mixers such as Cola, and soda water rushes through the stomach and intestinal walls into the blood stream, carrying alcohol with it and creating a rapid rise in BAL. A 0.08 BAL, for example, indicates approximately 8 parts alcohol to 10,000 parts other blood components. When a person drinks more alcohol than his or her body can eliminate, alcohol accumulates in the blood stream and the BAL rises.

Elimination of alcohol from a healthy adult body occurs at an average rate of approximately to 3/4 ounce per hour, the equivalent of 1 ounce of 100-proof whiskey, one large beer, or about 3 to 4 ounces of wine. When blood alcohol concentrations reach very high levels, the brain's control over the respiratory system may be paralyzed. A .30 BAL is the minimum level at which death can occur; at .40 the drinker may lapse into a coma. At .50 BAL, respiratory functions and heartbeat slow drastically, and at .60 most drinkers are dead.


The Liver:

Located in the upper-right side of the abdomen, the liver is the body's largest glandular organ. Its complex functions are associated with dozens of processes of body chemistry and metabolism. It produces the bile that helps digest fatty foods; it manufactures heparin, an anticoagulant, it stores and releases sugar. The liver also produces antibodies that help ward off disease, and it cleanses the body of poisons, including alcohol. With small amounts of alcohol, this cleansing can happen effectively. When the amount of alcohol is high, imbalances are created which can lead to hypoglycemia (low blood sugar), hyperuricemia (as in arthritis or gout), fatty liver (which may lead to hepatitis or cirrhosis), and hyperlipemia (build-up of fats sent to the bloodstream; which leads to heart problems).

The Central Nervous System:

The central nervous system (CNS) includes the brain, the spinal cord, and the nerves originating from it. Sensory impulses are transmitted to the CNS and motor impulses pass from it. When alcohol acts on the CNS, intoxication occurs, affecting emotional and sensory function, judgment, memory and learning ability. Smell and taste are dulled. The ability to withstand pain increases as the BAL rises.

Different parts of the brain seem to be affected by alcohol at different rates, creating alternate periods of restlessness and stupor. Long-term effects of alcohol on the central nervous system include tolerance, dependency, and irreversible damage. Changes in tolerance for alcohol, and the alcoholic drinker's dependency on alcohol, demonstrate that changes occur in the brain.

With each drinking episode, central nervous system functions deteriorate in a predictable sequence, beginning with intellectual functioning, followed by disturbances in sensory and motor control. Last affected are the automatic biological functions, such as breathing and heart action.

The brain is the organ that is most affected by alcohol, and proves that it is being damaged through the drinker's behavior changes and emotional distress. Three noticeable effects of alcohol injury to the brain: memory loss, confusion, and augmentation. (Augmentation is a physiological response to alcohol which results in hyper-alertness to normal situations, perceiving light as brighter or sounds as louder than usual, or the drinker’s becoming extremely sad or angry for no apparent reason.) The drinker's rapid mood swings and emotional and behavioral instability can be brought under control by stopping drinking.

Blackouts, or loss of memory for a period during drinking, are a physical effect of alcohol on the brain. They occur as alcohol cuts off the supply of oxygen to the brain. Lack of oxygen supply to the brain can kill tens of thousands of brain cells every time a person becomes intoxicated.

Another effect of alcohol on the brain is the "learned behavior syndrome"; when a behavior is learned under the influence of alcohol, the drinker sometimes must re-learn that behavior after stopping drinking.

The Blood:

One effect of drinking alcohol is "blood-sludging" where the red blood cells clump together causing the small blood vessels to plug up, starve the tissues of oxygen, and cause cell death. This cell death is most serious, and often unrecognized, in the brain. With this increased pressure, capillaries break, create red eyes in the morning, or the red, blotchy skin seen on the heavy drinker's face. Blood vessels can also break in the stomach and esophagus leading to hemorrhage, even death.

Other effects of alcohol on the blood include: anemia; sedation of the bone marrow (which reduces the red and white blood count, and weakens the bone structure); lowered resistance to infection; and a decrease in the ability to fight off infections.

The Gastrointestinal Tract:

The stomach, the small and large intestines, and the pancreas are each affected by alcohol. Alcohol increases acid in the stomach. That can result in gastritis or stomach or intestinal ulcers. The pancreas produces insulin which is necessary to regulate the amount of sugar in the blood. Drinking causes a steep rise in the blood sugar; the pancreas responds by producing insulin which causes a fast drop in blood sugar and the symptom of low blood sugar or hypoglycemia. 70-90% of alcoholics suffer to some degree from the disorder of hypoglycemia, chronic low blood sugar, as a long term effect of their drinking. Symptoms of hypoglycemia can include dizziness, headaches, lack of ability to concentrate, depression, anxiety, light-headedness, tremors, cold sweats, heart palpitations, loss of coordination, and upset stomach. In time, the drinker's overworked pancreas may stop producing insulin and diabetes can result. Conversely, a person with a family history of diabetes may be more vulnerable to problems with alcohol.

The Muscles:

Alcohol reduces blood flow to the muscles, including the heart, causing muscle weakness and deterioration. One outcome is cardiomyopathy (sluggish heart) which is common in alcoholics. Another outcome, arrhythmia (irregular heartbeat), or "holiday heart,"is often treated in emergency wards after several days of party drinking. Muscle aches are a common symptom of excessive-drinking "hangovers."

The Endocrine System:

This system controls the body's hormones and includes the pineal, pituitary, thyroid, and adrenal glands, and the ovaries or testes. Alcohol sedates these glands, resulting in under-production of hormones; effects include increased susceptibility to allergies. Alcohol can effect sexual functioning in various ways. In low doses, it lowers inhibitions and may make a person feel sexier; but in higher doses, it can decrease sexual functioning: in men, by decreasing the frequency of erections, decreasing the maintenance of erections, decreasing penile size during erection, and increasing the amount of time between erections, in women by interfering with normal processes of sexual stimulation, and blocking orgasmic response. With chronic and prolonged use of alcohol in men, there is a shrinkage of sex glands and an increase of the "female hormone" estrogen. This produces secondary sexual characteristics, such as enlarged breasts and a decrease in body hair. Prolonged use of alcohol can cause infertility in both men and women.


Tolerance: As people drink, their tolerance for alcohol may increase. They might seem to be able to "handle" alcohol better and need more to achieve the same effect as before. The liver does not become more tolerant, and is damaged over the course of time, leading to poor liver function and a noticeable decrease in tolerance, or "reverse-tolerance". A heavy drinker's reverse-tolerance is a sign of late-stage alcoholism.

Withdrawal: The effects of alcohol on the body account for the sick, uncomfortable, shaky feelings following a period of drinking. Withdrawal symptoms vary in intensity according to the amount and prolonged frequency of drinking.

Symptoms of alcohol withdrawal include:

  • hangovers -- fairly common result of overindulging-- headache, fatigue, thirst, and nervousness. There may be nausea and abdominal cramping. Diagnosed alcoholics report fewer hangovers than drinkers who are non-alcoholic, this may be because they have learned to ignore the symptoms.
  • sleep disturbance -- waking up earlier than usual after expecting to "sleep it off," being unable to fall asleep, disturbed dreaming.
  • irritability, anxiety, and restlessness -- all caused by the irritant effects of alcohol.
  • tremors, or "morning shakes"-- Tremors will clear after several days of abstinence, if there is no permanent damage to the nervous system
  • physical weakness, rapid heart rate,
  • mental sluggishness
  • difficulty thinking clearly or flexibly

All the above are lingering evidence of alcohol's impact on muscles, heart and brain.

For the drinker with only a mild degree of physical dependence, withdrawal effects may not extend beyond the symptoms listed above.

Some drinkers experience second stage withdrawal, marked by:

  • convulsions -- seizures usually occur between 12 and 48 hours of the last drink. There may be a loss of consciousness and body control.

Third stage withdrawal symptoms involve:

  • alcoholic hallucinosis and delirium tremens -- auditory, visual and tactile hallucinations occur. This period may last for three to four days, during which the de-toxifying person is in a severe state of agitation, is often completely disoriented and sleeps little, if at all. The delusions are almost always terrifying and may produce violent behavior. There is a 10%-20% mortality rate associated with this stage of withdrawal. Detoxification of the acutely ill alcoholic requires medical supervision.


Female drinkers reach higher blood alcohol levels (BAL's) faster because of less water and more fat in the body and because of differences in digestive enzymes. Women develop alcohol-related disorders such as brain damage, cirrhosis and cancers at lower levels of drinking than men. It is also known that the menstrual cycle affects alcohol metabolism in women. Women have been shown to develop their highest BAL's immediately before menstruating, and their lowest on the first day of menstruation. This can be related to hormone level shifts. There is evidence which shows that premenstrual syndrome with its emotional and physical discomfort and de-stabilized blood-sugar levels can trigger excessive drinking by some women.


Women who drink during pregnancy risk the development of both mental and physical defects in their children. Effects on the child can include: growth deficiencies; poorly formed bones and organs, heart abnormalities, cleft palate, retarded intellect, delayed motor development, poor coordination, behavior problems, and learning disabilities. Smoking cigarettes, combined with alcohol use, will increase the chance of birth defects. Use of alcohol increases the chance of miscarriage. It is best that a woman avoid alcohol, cigarettes, caffeine, and other drugs entirely during pregnancy. Antabuse is not a suitable treatment for the pregnant or potentially pregnant alcoholic woman; it interferes with maternal liver function and may cause harm to the developing fetus.

Since harm to the infant may result even before a woman realizes that she is pregnant, women who might become pregnant need to be particularly cautious about what they consume.


Secondary Diabetes: Diabetes can result from prolonged, excessive use of alcohol. Because it is caused by drinking and not from a genetic disorder, it is called "secondary" diabetes. The symptoms are identical to genetic or "primary" diabetes. Abstinence from alcohol is a vital part of treatment for this disorder.

Vitamins and Proteins: Those who use alcohol excessively deprive their bodies of essential nutrients. The drinker and the recovering alcoholic must pay special attention to diet. A diet high in protein not only provides many of the nutrients vital to recovery, but also keeps the blood sugar from too rapid change. It is better for those who drank excessively to get protein from eggs, milk, or vegetables, than from meats or cheeses. Because of an already-fatty liver, excessive drinkers cannot process the extra fat. When they eat meat, fruit should be eaten; it aids in breaking down fats. Vitamin supplements are helpful for people with drinking problems: these include, vitamins A, B, C and E. Protein supplementation may be important to reducing alcohol craving and maintaining emotional balance for alcoholics wanting to recover from their past heavy drinking. Similarly, a diet high in complex carbohydrates stabilizes blood glucose and reduces the low blood sugar state that can lead to craving alcohol. Understanding one's own special nutritional needs is an important aspect of recovery from excessive alcohol use.


Drugs such as marijuana and cocaine which are used, like alcohol, for "recreational" purposes have different, but similarly harmful, physical effects.

Research on marijuana use has shown several severe emotional and physical effects:

Frequent use can lead to the "amotivational syndrome", in which the person becomes apathetic, loses the ability to set realistic goals, lacks drive and ambition.

An active ingredient of marijuana (THC) settles in the fatty tissues of the body, especially in the reproductive organs. Male hormone levels drop and there is an increased level of impotence. Drop in hormone levels for women will affect the menstrual cycle and may result in a higher incidence of miscarriages.

Marijuana has from 7 to 10 times as much tar as one cigarette, increasing the chances of lung damage and emphysema. The chemistry of marijuana is extremely complex, dried marijuana contains over 420 chemical compounds--Delta 9 THC is generally cited as the psychoactive ingredient of marijuana, but research suggests that other compounds acting independently or interacting with Delta-9-THC also contribute to the intoxicating potency of the drug. While stored in body fats, THC and its metabolites are slowly released back into the bloodstream. Complete elimination of a single dose can take 30 days.

Given the slow clearance of marijuana's chemicals from the body, researchers predict that repeated use of marijuana at intervals of less than 8 to 10 days results in accumulation of THC and other psychoactive substances in the tissues of body and brain.

If marijuana is used with alcohol, the effect is greater than if the two effect patterns were added together.

Driving after using either alcohol or marijuana is unsafe, after using both, driving is more than twice as dangerous. Judgment, reaction time, and coordination are worse than with either drug taken alone.

Cocaine, "Crack" and amphetamines are fast-acting stimulants. People who use alcohol and stimulant drugs together will drink more to feel the effects of alcohol because of the stimulant effects. When stimulant effects wear off, the alcohol effects "catch up" quickly, and that can be extremely dangerous, both in terms of physical effects and distortions of perception and judgment.

Stimulants are also quickly-addicting drugs which cause their users to need more and more to get the same "high". Chronic stimulant use leads to dysphoria--a depressed, low-energy state; flattened emotions, a lack of interest in sex, and physical immobility.

The physical and psychological consequences of heavy stimulant use include: hallucinations and delusions, a mental state that appears "really crazy." Many stimulant users experience formication, the sensation that their skin is crawling with bugs. Impaired judgment and feelings of persecution are common. Users may overstimulate their heart muscles and cause sudden death from a single heavy dose.


Drugs prescribed for medical conditions are frequently harmful if combined with alcohol. Addiction to alcohol is addiction to all sedatives. Drugs which are prescribed to combat anxiety include various sedatives, "tranquilizers" and barbiturates; most frequently prescribed is Valium. Tranquilizers are addictive, and, if taken with alcohol will multiply the effects of both to sedate the user. This interactive effect can lead to a coma or death. Sometimes antidepressants, or amphetamines, are prescribed to treat depression or for weight control. These drugs speed up the nervous system and are addicting. Because they are stimulants, the effects of drinking while using them is like the effect of cocaine with alcohol -- they "cancel each other out" until the stimulant wears off, then intoxication occurs quickly.

Medication of any kind should not be mixed with alcohol. None should be taken by the recovering person, unless the physician who prescribes is fully aware of the alcohol use history.

Over-the-counter or "ordinary" medicine such as cold tablets or cough medicine are frequently used without caution. Drugstore medicines can have dangerous effects when mixed with each other, with alcohol, or when taken by the recovering alcoholic. Read the label. Ask the druggist.