What are alcohol's effects on the body?

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Ethanol, the type of alcohol found in alcoholic beverages, is a colorless, flammable substance with psychoactive (mind-altering) properties. 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. Moderate intake of alcohol can have some health benefits; however, excessive or prolonged use has many detrimental effects on the body.
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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.

Alcohol is a central nervous system (CNS) depressant; small amounts can produce euphoria and relaxation while large amounts can result in coma or death. Furthermore, moderate alcohol intake (a maximum of one or two drinks per day) may have some health benefits; excessive and regular consumption can be severely detrimental to one’s health.

Different degrees of BAC produce different effects, including euphoria, lethargy, mental confusion, stupor, vomiting, and coma. These effects are outlined here.

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, the person may laugh more readily, be friendlier, become more socially aggressive, or do things he or she would not normally do. Of note, a BAC of 0.08 percent, the threshold for driving under the influence, is set for every US state.

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, the person may forget phone numbers, addresses, or where he or she has parked a car. Driving or operating machinery could result in serious injuries or fatalities. If walking, the person could 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 the 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 his or her 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 at this point is not uncommon.

Aftereffects from an acute drinking episode persist for up to twenty-four hours. Consumption of alcohol within several hours before going to sleep results 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, results in the disruption of sleep patterns and prevents a restful night’s sleep. The person falls asleep promptly; however, once most of the alcohol has been metabolized, the person experiences (because of a rebound effect) episodes of wakefulness and light, unproductive sleep. The following morning, the person who consumed two or more alcoholic beverages awakens fatigued and may 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.

A single episode of drinking at the euphoric level (BAC of 0.03 to 0.12 percent) can have long-term consequences. Inappropriate comments or behavior while under the influence can result in the breakup of a relationship or the loss of a job. Driving under the influence—even if below the legal limit of 0.08 percent––can result in a traffic accident, which might cause serious injuries.

Long-Term Effects

In general, regular abusers of alcohol fall into two categories of use: alcoholism and alcohol abuse. Alcoholism is a chronic condition in which a person depends on regular ingestion of alcoholic beverages. 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 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 are caused by the direct effects of alcohol on the body and by resultant 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 include diabetes, an impaired immune system, kidney infections and kidney failure, pneumonia, gastritis (inflammation of the stomach) and esophagitis (inflammation of the esophagus), and the following, all of which are common in alcoholics:

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 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 his or her spouse, children, friends, and coworkers).

Fetal Alcohol Spectrum Disorder

Fetal alcohol spectrum disorder (FASD) is a general category for the long-term effect of alcohol consumption on the fetus of a pregnant woman who also is an alcoholic. 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, mental retardation, 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 woman stops drinking when she learns that she is pregnant.

A February 2011 study found that counseling about alcohol use during pregnancy is often inadequate. A study of 12,611 women who delivered infants from 2001 through 2008 found that, despite the substantial number of women who continue to consume alcohol during pregnancy, health care providers do not routinely assess alcohol consumption or counsel all women about alcohol’s harmful effects. As with other alcohol-related disorders, nutrition and other factors (such as abuse of prescription drugs or illegal substances) play a role in the development of FASD.

A safe level of alcohol consumption, which will prevent FASD, is not known; however, no cases of FASD have been reported in which the pregnant woman consumed an occasional alcoholic beverage or even consumed a larger amount on a few occasions. A 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.

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, studies have found that heroin addicts who had given up the drug for more than one year found it more difficult to quit smoking than breaking a heroin habit. Other studies have found that it is more difficult to quit smoking than to quit using 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. Reports have shown that more than 70 percent of fatal heroin overdoses are caused by the co-ingestion of heroin and another depressant, such as alcohol. 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 his or her 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 a 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 is offered a cup of coffee 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 (up to three drinks per occasion or seven drinks per week) may have some health benefits. This level of drinking might reduce the risk of heart disease, of dying from a heart attack, and of developing gallstones, and it might possibly reduce the risk of stroke and diabetes. Drinking red wine might be particularly beneficial. The so-called French paradox observes that the French have a relatively low incidence of coronary artery disease, despite high rates of smoking, low rates of exercise, and high rates of diets that are relatively high in saturated fat. The answer to this paradox might lie in the consumption of red wine by the French.

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. Despite the positive evidence, the health benefits of resveratrol are subject to controversy. The appetite-stimulating properties of alcohol have been found to benefit the elderly, whose health can suffer from a lack of appetite. A variety of tonics containing alcohol are on the market, and they often improve appetite. They also often improve sleep patterns.


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