Alcohol's effects on the body

Consumption of alcohol—typically in the form of ethanol in alcoholic beverages—is common in human society around the world. Alcohol is considered a psychoactive drug and a depressant, with known toxic, carcinogenic, and dependency-forming qualities. It is well established among scientists and health professionals that alcohol consumption has many detrimental effects on the body, especially with excessive or prolonged use. Some research has suggested that limited consumption might have certain health benefits, but such claims are controversial.

Short-Term Effects

Alcohol is absorbed into the bloodstream through the lining of the stomach, so measurable amounts can be present within five minutes of ingestion. If alcohol is consumed after eating a heavy meal, its absorption is slowed. Alcohol is metabolized (broken down) in the liver. One to two hours are required to metabolize one drink.

The amount of alcohol in the body is usually measured as the blood alcohol content (BAC), expressed as the percentage of alcohol per liter of blood. Different degrees of BAC produce different effects, including euphoria, lethargy, mental confusion, stupor, vomiting, and coma.

• Euphoria (BAC of 0.03 to 0.12 percent). Symptoms include improved mood, increased sociability, increased self-confidence, increased appetite, inhibited judgment, impaired fine-muscle coordination, and flushed appearance. At this level, a person may laugh more readily, be friendlier, become more socially aggressive, or do things they would not normally do. Of note, a BAC of 0.08 percent is set as the threshold for driving under the influence in the United States.

• Lethargy (BAC of 0.09 to 0.25 percent). Symptoms include impaired comprehension and memory, sedation, slowed reflexes, blurred vision, and ataxia (lack of coordination), which is manifested by difficulties in balancing and walking. At this level, a person may forget phone numbers, addresses, or where they parked a car. Driving or operating machinery could result in serious injuries or fatalities. If walking, the person may be more prone to trip or fall.
• Mental confusion (BAC of 0.18 to 0.30 percent). Symptoms include pronounced confusion, labile emotions (abrupt mood changes, laughing or crying readily), increased ataxia, decreased pain sensation, slurred speech, staggering, sensory impairment (sight, hearing, and touch), vomiting, and dizziness, which is often associated with nausea. This level is sometimes referred to as falling-down-drunkenness, and a person at this level of intoxication is severely impaired.
• Stupor (BAC of 0.25 to 0.40 percent). Symptoms include severe ataxia, vomiting, unconsciousness (may be intermittent), slowed heart rate, slowed respirations, and urinary incontinence. At this level, death can occur from respiratory depression or from vomiting (if while unconscious, the person aspirates vomit into their lungs).
• Coma (BAC of 0.35 to 0.50 percent). Symptoms include unconsciousness, markedly depressed reflexes (for example, pupils do not respond to light), severe respiratory depression, and severely slowed heart rate. At this level the drinker has alcohol poisoning, and death is not uncommon if left untreated.

Aftereffects from an acute drinking episode persist for up to twenty-four hours. Consumption of alcohol within several hours before going to sleep may result in the drinker falling asleep more promptly. Consumption of one alcoholic beverage may increase total hours of sleep and may decrease awakening during the night. Higher consumption, however, often results in the disruption of sleep patterns and prevents a restful night’s sleep. The person may still fall asleep promptly; however, once most of the alcohol has been metabolized, they tend to experience episodes of wakefulness and light, unproductive sleep. High consumption may also cause a person to awaken fatigued and experience a hangover, which can include headache, nausea, thirst, sensitivity to light and noise, diarrhea, and dysphoria (depression, anxiety, and irritability). Some of these symptoms are caused by dehydration, which can occur even with moderate alcohol consumption.

The immediate effects of even a single episode of drinking at the euphoric level (BAC of 0.03 to 0.12 percent) can also potentially have longer-term consequences. For example, inappropriate comments or behavior while under the influence might result in the breakup of a relationship or the loss of a job. Driving under the influence—even if below the legal limit—could result in a traffic accident, which might cause serious injuries.

Long-Term Effects

Most scientists and health professionals agree that alcohol consumption, even at moderate levels, causes an elevated risk of many long-term health problems. Notably, alcohol is classified as a high-risk carcinogen, and is associated with numerous forms of cancer. As a result, groups such as the World Health Organization (WHO) have stated that there is no "safe" level of alcohol consumption.

Nevertheless, much of the focus on the long-term effects of alcohol continues to focus on excessive consumption or "problem drinking." While definitions vary, regular abusers of alcohol are often divided into two categories of use: alcoholism and alcohol abuse. Alcoholism is a chronic condition in which a person becomes dependent on regular ingestion of alcoholic beverages. People with alcoholism, sometimes called alcoholics, are unable to control their drinking and continue to drink even when doing so interferes with their health, interpersonal relationships, and work.

Alcohol abuse is excessive drinking—enough to cause problems in daily life—without the person necessarily having complete dependence on alcohol. The long-term effects of regularly consuming more than one or two alcoholic beverages are profound and include medical, neuropsychiatric, and social problems. Both alcoholics and alcohol abusers are more susceptible to the long-term effects of alcohol abuse. These may be caused by both the direct effects of alcohol on the body and related poor nutrition. Heavy drinkers may have a poor diet because much of their caloric intake often comes from alcoholic beverages.

Long-term alcohol abuse has medical, neuropsychiatric, and social consequences. Medical effects can include diabetes, an impaired immune system, kidney infections and kidney failure, pneumonia, gastritis (inflammation of the stomach) and esophagitis (inflammation of the esophagus). Other conditions can include the following:

• Cancer. Includes many forms of cancer, such as throat, esophagus, stomach, colon, rectum, liver, and kidney cancers. The combination of tobacco and alcohol markedly increases the risk of cancer, particularly cancers of the mouth and throat.
• Cardiovascular disease.Hypertension (high blood pressure), heart failure, cardiomyopathy (damage to the heart muscle), and stroke.
• Pancreatitis (inflammation of the pancreas). Acute pancreatitis is the sudden onset of inflammation, which may result in death. Chronic pancreatitis can continue for many years and can ultimately lead to death.
• Ulcers of the stomach or duodenum (upper portion of the stomach). A perforated ulcer is a life-threatening situation.
• Cirrhosis of the liver. This condition can lead to liver failure and death. Cirrhosis can produce portal hypertension (increased blood pressure in the venous system within the liver). Portal hypertension can produce esophageal varices (dilated blood vessels in the esophagus). Esophageal varices are prone to rupture and can result in a fatal hemorrhage.
• Vitamin deficiencies. Vitamin deficiencies, which are usually caused by a poor diet, can result in a number of severe health problems.
• Obesity. The appetite-stimulating effect of alcohol coupled with the calories in alcohol can result in obesity in some alcohol abusers.

Long-term neuropsychiatric effects of alcohol abuse include confusion; impaired memory; dementia; antegrade amnesia (also known as blackouts, the loss of memory following an episode of heavy drinking); tremors; peripheral neuropathy (numbness of the feet and hands); hallucinations (auditory and visual); fear, anxiety, and a sense of impending doom; an obsession with drinking; sexual dysfunction, including decreased libido and erectile dysfunction (inability for a male to get an erection); and delirium tremens, or DTs (tremors or convulsions). DTs occur during an episode of withdrawal from alcohol.

Long-term social effects of alcohol abuse include elevated risk of traffic fatalities or injuries to self or others, dysfunctional home life, spousal battery, child abuse, disruption of interpersonal relationships outside the home, injury or accidents at work, loss of a job or promotion, and codependency (a condition in which an alcoholic manipulates or controls others, such as a spouse, children, friends, and coworkers).

Fetal Alcohol Spectrum Disorder

Fetal alcohol spectrum disorder (FASD) is a general category for the long-term effects on a fetus from alcohol consumption while pregnant. FASD involves varying degrees of physical and mental abnormalities. The best known and most thoroughly researched form of FASD is fetal alcohol syndrome (FAS).

Children with FAS are often born with a low birth weight and have varying degrees of facial abnormalities, CNS disorders, skeletal abnormalities, and heart defects. The facial abnormalities include microcephaly (small head and brain), small eyes, thin upper lip, and a small, upturned nose. The CNS disorders include vision and hearing problems, poor coordination, learning disabilities, and sleep problems. The skeletal abnormalities include deformities of the limbs, joints, and fingers. The heart defects include atrial septal defects (defects in the wall separating the upper heart chambers) and ventricular septal defects (defects in the wall separating the lower heart chambers).

Two other forms of FASD are alcohol-related neurodevelopmental disorder (ARND) and alcohol-related birth defect (ARBD). Persons with ARND may have intellectual, behavioral, and learning disabilities. During childhood, they tend to perform poorly in school and have difficulties with mathematics, attention, judgment, memory, and impulse control. Persons with ARBD have abnormalities that include hearing problems and problems of the heart, skeletal system, and kidneys.

Affected children cannot be cured; however, the following factors can improve a child’s quality of life: early recognition of the disorder (before the age of six years); enrollment in special education programs; and a nurturing, stable, home environment. FASD is preventable if a person stops drinking when they learn that they are pregnant.

There is no established threshold of alcohol consumption during pregnancy that will definitively avoid FASD. One large study (11,513 children) published by researchers at University College London in October 2010 found that children at age five years who were born to women who drank one or two alcoholic beverages per week during pregnancy were not at increased risk for any behavioral or cognitive problems. However, a study published in JAMA in 2017 showed an association between all levels of prenatal alcohol exposure and the minor changes in the shapes of the newborns' faces when measured at twelve months. This study concluded that avoiding all alcohol by mothers is the safest option.

Alcohol Combined with Other Substances

Many abusers of alcohol also abuse other substances. Sometimes, the combination has a synergistic effect—the combined effect is significantly more harmful than either substance alone. These harmful effects can occur with both short- and long-term use of alcohol plus another substance or substances. These substances include tobacco, marijuana, CNS depressants, CNS stimulants, prescription drugs, and over-the-counter (OTC) medications.

Tobacco. The combination of alcohol and tobacco greatly increases the risk of many types of cancers. The risk of oral (mouth and tongue) cancer is extremely high in smokers (or tobacco chewers) who also drink alcohol in excess. Smoking is a particularly difficult habit to quit. For example, some studies have suggested that it is more difficult to quit smoking than to quit using heroin or cocaine.

Marijuana. Marijuana is a commonly used recreational drug and is frequently used with alcohol. The combination of the two can be particularly lethal. Vomiting after having overindulged in alcohol removes some of the alcohol from the stomach, but this reflex is suppressed with marijuana. As a result, more alcohol remains in one’s system, increasing the chance of alcohol poisoning. Even small amounts of alcohol and marijuana increase the risk of a traffic accident. Alcohol slows reaction time and alertness, and marijuana further impairs the driver. For example, marijuana reduces the frequency of a driver’s visual searches (that is, of looking right and left before entering an intersection or before changing lanes).

CNS depressants. Alcohol is a CNS depressant. Co-ingestion (mixing) of alcohol and other CNS depressants, such as heroin, barbiturates, tranquilizers, analgesics (pain relievers), and sedatives, is particularly harmful. The drug interaction can lead to depressed breathing and slowed heart rate, resulting in unconsciousness. The unconscious state can progress to coma and death. While unconscious, the person may vomit and aspirate the vomitus into their lungs, which frequently causes death.

CNS stimulants. CNS stimulants, such as cocaine, methamphetamine, and caffeine, interact with alcohol. Researchers have found that cocaine and alcohol combine in the liver to produce cocaethylene, which intensifies the euphoric effect of cocaine. Cocaine by itself has been associated with sudden death; however, cocaethylene is associated with a greater risk of sudden death than cocaine alone. Methamphetamine is another potent stimulant. Studies have suggested that when combined with alcohol, it increases the risk of alcohol poisoning. Caffeine is a mild stimulant, compared with cocaine and methamphetamine. However, the combination of alcohol and caffeine has added risks. Not uncommonly, a person who has overindulged may drink coffee in an effort to “sober up.” However, the caffeine in the coffee does not improve sobriety—it merely produces a state of wide-awake drunkenness. The increased alertness coupled with the augmented self-confidence from alcohol increases the risk of unsafe activity, such as driving an automobile.

Prescription or nonprescription medication. Many prescription drugs, such as antipsychotics and antidepressants, interact with alcohol. In addition, some OTC products, such as sleep aids and cold remedies, also may have an interaction. It is prudent for one taking any medication to read the label of the medication before consuming alcohol.

Moderate Alcohol Intake

Moderate drinking (often defined as up to three drinks per occasion or seven drinks per week) is widely considered socially acceptable in many cultures, and may even be typical behavior in some populations. Historically, there have also been many suggestions that moderate drinking may have some health benefits. These range from folk traditions such as using alcohol as a sleep aid or hangover remedy to scientific research proposing a possible link between moderate alcohol consumption and reduced the risk of heart disease or other health disorders. By the 2020s, the scientific consensus had evolved to hold that any level of alcohol consumption brings health risks that outweigh any potential positive or protective effects. Nevertheless, the issue of possible health benefits of alcohol continued to be debated and covered in the media.

Drinking red wine has often been touted as the most likely beneficial form of alcohol consumption. Red wine contains resveratrol, which is an antioxidant. Experimental evidence shows that resveratrol may have anti-inflammatory, anticancer, and blood-sugar-lowering properties, all of which promote cardiovascular health. However, any potential health benefits of resveratrol in wine has not been conclusively demonstrated, and the concept is subject to controversy. The WHO and other experts tend to note that studies indicating protective effects of alcohol are often statistically limited or otherwise flawed.

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