Alcoholic beverages owe their intoxicating effects to ethanol, a chemical compound that causes changes in perception, mood, and coordination. Understanding how ethanol interacts with the body provides insight into the experience of intoxication.
The Key Component: Ethanol
Ethanol, also called ethyl alcohol, is a clear, colorless liquid with a distinctive odor and taste. It is a simple alcohol molecule with the chemical formula C2H5OH. This compound is produced through the fermentation of sugars found in grains, fruits, and vegetables by yeast. All alcoholic drinks, whether beer, wine, or spirits, contain ethanol, which is solely responsible for their intoxicating effects.
Ethanol is highly soluble in water and mixes readily with many organic liquids. Its small, uncharged molecular structure allows it to easily cross biological membranes. This property enables ethanol to rapidly diffuse throughout the body’s tissues and fluids, including the brain, after absorption.
How Ethanol Affects Your Brain
Once absorbed into the bloodstream, ethanol quickly reaches the brain, where it acts as a central nervous system depressant. It achieves its effects primarily by interacting with neurotransmitters, the chemical messengers that transmit signals between brain cells. This interaction results in the characteristic signs of intoxication.
Ethanol enhances the activity of gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain. By binding to specific sites on GABA-A receptors, ethanol increases the influx of chloride ions into neurons, which makes them less excitable. This heightened inhibition contributes to feelings of relaxation, sedation, reduced anxiety, as well as impaired motor coordination and slurred speech.
Ethanol inhibits the function of glutamate receptors, particularly the N-methyl-D-aspartate (NMDA) subtype. Glutamate is the brain’s main excitatory neurotransmitter, involved in learning and memory. By suppressing glutamate activity, ethanol further slows down brain function, contributing to impaired judgment, memory lapses, and difficulties with cognitive processes.
Ethanol also influences the brain’s reward system by increasing the release of dopamine, a neurotransmitter associated with pleasure and motivation. This surge in dopamine contributes to the initial euphoria often experienced during alcohol consumption. However, prolonged alcohol use can lead to the brain adapting by producing less dopamine, which may contribute to cravings and continued drinking.
Factors Shaping Your Intoxication
Intoxication varies significantly among individuals and even within the same person. Several factors influence how alcohol affects someone, including body weight, as individuals with more body water tend to have a lower blood alcohol concentration (BAC) for the same amount of alcohol consumed.
Gender plays a role due to differences in average body water content and enzyme activity. Women tend to have a higher BAC than men after consuming the same amount of alcohol because they have a lower percentage of body water and may have less of the enzyme alcohol dehydrogenase in their stomach.
Food consumption before or during drinking also impacts the rate of alcohol absorption. Eating slows down the emptying of alcohol from the stomach into the small intestine, where most absorption occurs. This delay reduces the speed at which alcohol enters the bloodstream, leading to a more gradual rise in BAC. Other factors, such as the speed of consumption and the alcohol concentration of the beverage, directly affect how quickly ethanol reaches the bloodstream and brain. Higher concentrations and faster consumption rates lead to more rapid intoxication.
How Your Body Processes Alcohol
Once ethanol enters the bloodstream, it distributes throughout the body’s water-containing tissues. The liver primarily processes and eliminates alcohol through a series of metabolic steps, metabolizing about 90-98% of consumed alcohol.
The initial step in alcohol metabolism involves the enzyme alcohol dehydrogenase (ADH), which converts ethanol into acetaldehyde, a toxic compound. Acetaldehyde is then rapidly broken down by another enzyme, aldehyde dehydrogenase (ALDH), into acetate, which is much less toxic. Acetate is further metabolized into carbon dioxide and water, which are then eliminated from the body. A small percentage, about 2-10%, of alcohol is excreted unchanged through breath, urine, and sweat.
The rate at which the liver can process alcohol is relatively constant. This rate is approximately one standard drink per hour. If alcohol is consumed faster than the body can metabolize it, the amount of alcohol in the bloodstream increases, leading to higher levels of intoxication. Blood Alcohol Content (BAC) is a measure of the amount of alcohol in the blood, expressed as a percentage. A BAC of 0.08%, for instance, means there are 0.08 grams of alcohol per 100 milliliters of blood.