The consumption of alcoholic beverages introduces ethanol, a small, water-soluble molecule, into the body. Ethanol is not digested like food but is rapidly absorbed directly into the bloodstream through the stomach and, primarily, the small intestine. Within minutes, ethanol is distributed throughout the body’s water content, affecting various organs, including the brain. The body treats this substance as a compound that must be eliminated, initiating a series of chemical reactions.
How the Body Processes Alcohol
The primary mechanism for removing alcohol is metabolism, which occurs overwhelmingly in the liver. The liver is responsible for breaking down over 90% of the ethanol consumed, converting it into less harmful compounds. This initial conversion is carried out by the enzyme Alcohol Dehydrogenase (ADH).
The ADH enzyme transforms ethanol into a highly reactive and toxic substance called acetaldehyde. Because acetaldehyde is harmful, the body must quickly process it further. A second enzyme, Aldehyde Dehydrogenase (ALDH), converts the acetaldehyde into acetate.
The resulting acetate is a harmless compound that the body can use as an energy source or break down further into carbon dioxide and water. This two-step enzymatic process establishes the rate at which the body can process alcohol. The rate of metabolism is relatively constant, averaging a reduction in blood alcohol concentration of approximately 0.015% per hour.
The Primary Exit Routes for Alcohol
While the liver’s metabolic activity handles the vast majority of alcohol, a small percentage of the unmetabolized ethanol is removed from the body directly. This direct removal accounts for about 2% to 10% of the total alcohol consumed. These processes are collectively known as excretion.
The two main channels for this excretion are the lungs and the kidneys. Alcohol is volatile, meaning it easily evaporates, and when blood carrying ethanol travels to the lungs, some of the alcohol transfers into the air sacs (alveoli), which is what breathalyzer devices measure.
The kidneys filter the blood, removing some unmetabolized ethanol, which is then eliminated in urine. A very small amount is also expelled through the skin in sweat. These excretion routes remove the original ethanol molecule, distinguishing them from the metabolic process.
The Role of Feces in Alcohol Elimination
The idea that defecation assists in alcohol removal is not supported by the body’s absorption and elimination pathways. Alcohol is absorbed very quickly, with approximately 20% entering the bloodstream from the stomach and the remaining majority absorbed rapidly in the small intestine. This process is so efficient that very little ethanol makes it further down the gastrointestinal tract.
The contents that eventually become feces are primarily undigested food matter, fiber, and dead cells that pass into the large intestine. Since ethanol is absorbed almost entirely before reaching the large intestine, virtually no alcohol is left to be expelled in the stool. Therefore, defecation plays no meaningful role in reducing blood alcohol concentration.
The final breakdown products of alcohol metabolism—carbon dioxide and water—are eliminated through breath and urine, not through the stool. The speed of sobering up is determined by the liver’s fixed metabolic rate, not by waste elimination.