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Understanding Alcohol's Effects

What happens when you drink an alcoholic beverage? Although alcohol affects different people in different ways, in general, it is quickly absorbed from your digestive system into your blood. The amount of alcohol in your blood reaches its maximum within 30 to 45 minutes after your last drink, according to the National Institute on Alcohol Abuse and Alcoholism (NIAAA).

Alcohol is metabolized — that is, broken down chemically so it can be eliminated from your body — more slowly than it is absorbed. You can become more intoxicated as you drink more alcohol than is eliminated, which will result in an increase in your blood alcohol level.

A standard drink is considered to be 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits — all of these contain the same amount (approximately 15 grams or 1/2 ounce) of alcohol. 

Your genetics, body weight, gender, age, the type of beverage, food in your stomach, medications in your system, and your state of health, all influence how you respond to alcohol.

Genetics

Alcohol is broken down through the work of 3 enzymes. Research shows that different people can have variations of the gene that produces these enzymes. The differences in these enzymes mean that some people metabolize alcohol differently from others. For instance, different levels of alcohol metabolizing enzymes cause facial flushing, nausea, and a rapid heartbeat in many people with East Asian heritage — making drinking unpleasant even when only moderate amounts are consumed. The NIAAA says that genetic differences in these enzymes may help to explain why some ethnic groups have higher or lower rates of alcohol-related problems.

Your weight

The extent of alcohol's effect on the central nervous system depends on how much is in your blood and how much blood you have. This is because alcohol is distributed through the body by the water in your bloodstream. The more water in your blood, the more diluted the alcohol will be.

Generally, the lower your body weight, the less blood and water you have. So, smaller people usually have a higher ratio of alcohol in their blood if they drink the same amount a heavier person drinks.

For most people, intoxication begins to occur after 2 to 3 drinks, but it can occur more quickly, with fewer drinks in a lighter person. Keep in mind that the alcohol content of different types of beer, wine, and distilled spirits can vary a lot.

Your gender

Men generally can drink more alcohol than women of the same size before they show its effects. This is because women have less body water than men of similar body weight. Because alcohol mixes with water, women tend to have a higher concentration of alcohol than men of the same weight after drinking the same amount of alcohol. Women also have lower levels of one of the enzymes that metabolizes alcohol, so the alcohol they drink stays in their bodies for a longer time. Therefore, with the same amount of consumption, a woman's brain and other organs are exposed to more alcohol and more of its toxic byproducts.

Your age

As people get older, they usually have a higher fat-to-muscle ratio and less body water, so with the same amount of intake they may have a higher concentration of alcohol in the blood than younger people of the same weight. In addition, many older people take prescription and over-the-counter (OTC) medications that may interact with alcohol. The slower reaction times and problems with seeing and hearing put older people who are intoxicated at higher risk for falls and traffic accidents. People older than age 65 who drink alcohol should limit themselves to no more than 1 drink a day.

What's in the drink

People tend to feel the effects of beer or wine a little less. This may be because the water in beer and wine creates more volume to drink compared with an equal amount of alcohol in hard liquor.

But the carbon dioxide in champagne or the soda in a mixed drink increases the rate of alcohol absorption, causing a more rapid effect.

How much food is in your stomach

How quickly alcohol is absorbed depends on how quickly the stomach empties its contents into the intestines. Foods high in fat take longer to leave the stomach. If you eat a meal, especially one containing fat, before drinking, alcohol absorption will be considerably slower than drinking on an empty stomach and your blood alcohol level will be lower.

The medications you take

Alcohol can influence the effectiveness of medications, including sleeping pills, blood thinners, and some antidepressant and antianxiety drugs. Any medications that can cause drowsiness, such as antianxiety or sleeping medications, some antidepressants and antihistamines, and many others, can increase alcohol intoxication when you drink. Be sure to ask your doctor or pharmacist if any of the medications you take can have this effect.

Your physical and emotional health

People who are fatigued or highly stressed often have a stronger reaction to moderate amounts of alcohol.

Alcohol and weight management

Alcohol contains significant calories — 7 calories in each gram. That's over 100 calories in each standard drink, not including any sugar, flavorings, and other ingredients. Drinking also may lead you to eat or overeat, especially when you are in a social setting.