Beer can make you drunk because it is an alcoholic beverage containing ethanol, the chemical compound responsible for intoxication. Ethanol enters the bloodstream and alters the central nervous system, causing intoxication. This effect is a predictable biological outcome, though the degree of intoxication varies widely among individuals and situations.
Alcohol Content and Beer Variety
The primary determinant of beer’s intoxicating effect is its Alcohol by Volume (ABV), which measures the percentage of pure ethanol contained within the total volume of the beverage. A higher ABV means a greater concentration of alcohol in every ounce consumed. Most common beers, such as light lagers, fall in the range of 4% to 6% ABV, with the average being around 5% ABV.
The category of “beer” is wide, including craft brews, imperial stouts, and barleywines that can easily exceed 8% or even 10% ABV. A standard drink contains 0.6 ounces of pure alcohol, typically found in a 12-ounce serving of 5% ABV beer. Stronger or larger servings contain significantly more than one standard drink. The total amount of pure alcohol consumed, calculated using the ABV and volume, determines the potential for intoxication.
How Alcohol Causes Intoxication
Intoxication begins the moment ethanol is consumed and rapidly absorbed, primarily through the small intestine, though some absorption occurs in the stomach. Once absorbed, the ethanol passes into the bloodstream and is distributed throughout the body’s water-containing tissues. This distribution is why alcohol affects the brain, as it crosses the blood-brain barrier easily.
The level of alcohol in the bloodstream is quantified as the Blood Alcohol Concentration (BAC), expressed as a percentage of alcohol per unit of blood. BAC is the direct measure of intoxication, correlating with a person’s behavior and impairment. Ethanol acts as a central nervous system depressant, meaning it slows down brain activity. It achieves this by interacting with neurotransmitters, particularly Gamma-aminobutyric acid (GABA), the brain’s main inhibitory chemical messenger.
Alcohol enhances the effects of GABA, which quiets or suppresses the activity of neurons. This increased inhibitory effect leads to the physical signs of drunkenness, such as impaired judgment, slowed reaction times, and reduced motor coordination. The liver begins metabolism almost immediately, using the enzyme alcohol dehydrogenase (ADH) to break down ethanol into acetaldehyde, a toxic compound. The liver can only process alcohol at a relatively fixed rate, meaning any excess remains in the bloodstream, contributing to the rising BAC and the feeling of being drunk.
Factors That Control How Drunk You Get
The speed and degree of intoxication from beer depend on several personal and situational factors. A person’s body size and composition play a significant role because alcohol is dispersed in total body water. Larger individuals, or those with a higher percentage of lean muscle mass, tend to have a greater body water content, which dilutes the alcohol more effectively, resulting in a lower peak BAC compared to smaller individuals consuming the same amount.
The presence of food in the stomach slows down the absorption rate of alcohol. Eating a meal before or while drinking beer prevents the stomach contents from emptying quickly into the small intestine, where most of the alcohol is absorbed. This slower absorption rate allows the liver more time to metabolize the alcohol, reducing the peak BAC.
Biological sex also affects how alcohol is processed. Females generally have a lower percentage of body water and lower levels of the stomach enzyme alcohol dehydrogenase compared to males. These differences mean that, even when adjusted for body weight, females often achieve a higher BAC and feel the effects of alcohol more quickly and intensely.
The rate at which beer is consumed is a major factor; rapid drinking overwhelms the liver’s ability to metabolize the ethanol, causing a faster and higher spike in BAC. Chronic alcohol use also leads to increased tolerance, where the central nervous system adapts to the presence of ethanol, requiring a higher BAC to achieve the same perceived level of intoxication. Certain medications can also amplify the depressant effects of alcohol, potentially leading to greater impairment at lower BAC levels.