Feeling “drunk” involves changes in mood, coordination, and judgment. This experience is the direct result of alcohol, specifically ethanol, interacting with the intricate systems of the human body and brain. Understanding this process involves exploring how alcohol enters the bloodstream, influences brain chemistry, and is eventually processed and eliminated.
How Alcohol Enters and Spreads Through the Body
Alcohol is absorbed directly into the bloodstream, unlike most foods. About 20% is absorbed through the stomach lining, with the majority absorbed more rapidly in the small intestine. Food in the stomach can slow this process by delaying alcohol’s passage into the small intestine.
Once absorbed, alcohol quickly enters the circulatory system and distributes throughout the body’s water-containing tissues and organs. The brain, with its high water content, receives a substantial share, leading to rapid effects on mental and physical functions. The full effects of a drink can be felt within 15 to 45 minutes, depending on absorption speed.
Alcohol’s Effects on the Brain
Alcohol acts as a central nervous system depressant, slowing down brain activity. It achieves this by interfering with neurotransmitters, the chemical messengers that transmit signals between brain cells.
Alcohol significantly enhances gamma-aminobutyric acid (GABA), the brain’s main inhibitory neurotransmitter. By increasing GABA activity, alcohol reduces neuronal excitability, leading to relaxation, sedation, and slowed brain functions. At the same time, alcohol suppresses glutamate, the brain’s primary excitatory neurotransmitter. This dual action disrupts the brain’s normal communication pathways.
These neurochemical changes lead to the characteristic signs of intoxication. Impaired coordination and balance stem from alcohol affecting the cerebellum, the brain region responsible for motor control. Poor judgment and decision-making are linked to its influence on the prefrontal cortex. Slurred speech and memory problems, including blackouts, also result from alcohol’s widespread depressive effects on various brain areas. Alcohol also stimulates the release of dopamine, a neurotransmitter associated with pleasure and reward, contributing to the initial euphoric feelings.
How the Body Processes Alcohol
Alcohol’s primary mechanism for elimination is through metabolism, predominantly in the liver, which breaks down 90-98% of consumed alcohol. This metabolism occurs in a two-step process involving specific enzymes.
First, alcohol dehydrogenase (ADH) converts ethanol into acetaldehyde, a toxic compound responsible for many unpleasant effects, including hangover symptoms. In the second step, aldehyde dehydrogenase (ALDH) breaks down acetaldehyde into acetate, a much less toxic substance that is then further metabolized into carbon dioxide and water.
The liver processes alcohol at a relatively constant rate, averaging about one standard drink per hour. If alcohol is consumed faster than the liver can process it, alcohol accumulates in the bloodstream, leading to increased intoxication. Only 2-10% of alcohol is eliminated unchanged through sweat, breath, and urine.
Why Intoxication Varies
The degree of intoxication varies significantly due to biological and situational factors. Body weight plays a role because alcohol distributes throughout the body’s water content; a larger person typically has more body water, which dilutes alcohol more effectively. This means that for the same amount consumed, a smaller person generally has a higher blood alcohol concentration.
Gender also influences intoxication levels. Women generally have less body water and less stomach alcohol dehydrogenase than men. These differences can lead to women experiencing alcohol effects more quickly and intensely. Genetic variations in ADH and ALDH enzymes also affect how efficiently individuals metabolize alcohol, impacting their susceptibility to intoxication and alcohol-related side effects.
Situational factors also contribute to variations in intoxication. Consuming food before or while drinking can slow alcohol absorption, leading to a lower and more gradual peak in blood alcohol concentration. The speed of consumption is another important factor; drinking quickly overwhelms the body’s ability to metabolize alcohol, resulting in faster and higher intoxication. Sipping drinks slowly allows the body more time to process alcohol. Carbonated beverages can also increase the rate of alcohol absorption.