Alcohol is absorbed, in large part, from the stomach lining directly into the bloodstream. What isn’t directly absorbed through the stomach is absorbed shortly thereafter, through the first part of the intestinal tract. This is why drinking with a meal can slow the absorption of alcohol.
The reason why cirrhosis of the liver is a common, often fatal, condition in alcoholics is because some of the alcohol reaches the liver even before it gets up to the brain. The liver immediately begins working on this foreign substance in the blood and starts converting it, with the help of enzymes.
The liver uses six different enzymes to convert alcohol from ethanol (alcohol’s scientific name) to acetaldehyde. Ironically, the acetaldehyde is more toxic than the ethanol, but that is not the last step. The liver must then work to change the acetaldehyde to acetaldehyde dehydrogenase. This is a non-toxic substance called acetic acid.
The six enzymes working on this molecular alteration are called, as a group, alcohol dehydrogenase. The liver has to work hard to process through these steps of metabolizing alcohol. Thus, the liver is usually one of the first organs to be damaged with excessive alcohol consumption.
What the liver does not metabolize is secreted through the person’s urine, feces, sweat, saliva, breath, and mother’s milk. The alcohol that is released through the breath is used as a measurement for blood alcohol content (BAC) on roadside tests. But ironically, only 5% of alcohol is excreted through the aforementioned methods. 95% of the alcohol a person consumes is metabolized by the liver.