The Anatomy of a DUI – Absorption of Alcohol

In my last article I provided a brief overview of alcohol, mainly ethanol, which is the type of alcohol consumed by humans in alcoholic beverages.  Ethanol is produced through the process of fermentation (up to 15%) and by distillation for beverages with higher alcohol concentrations such as rum, vodka, whiskey, etc.  In this article I will discuss how alcohol is absorbed into the body.

13070400_mAlcohol is a Central Nervous System Depressant. It doesn’t affect a person until it gets into their central nervous system, i.e., the brain, brain stem and spinal cord.

Alcohol gets to the brain by getting into the blood. In order to get into the blood, it has to get into the body.  There are actually a number of different ways in which ethanol can get into the body (think creatively), but the most common method is by drinking alcohol beverages.


Once the ethanol gets into the stomach, it has to move into the blood. The process by which this happens is known as absorption. One very important fact is that alcohol doesn’t have to be digested in order to move from the stomach to the blood.  The ideal circumstance for rapid absorption is to drink on an empty stomach.  When the alcohol enters the empty stomach, about 20 percent of it will make its way directly through the stomach walls. The remaining 80 percent will pass through the base of the stomach and enter the small intestine where it is absorbed into the blood. Because the body doesn’t need to digest the alcohol before admitting it into the bloodstream, the small intestine will be open to the alcohol as soon as it hits the stomach.

But what if there is food in the stomach? If a person has eaten before drinking, or eats food while drinking, this will slow the absorption of alcohol.  Food has to be digested in the stomach before it can pass to the small intestine. When the brain senses that food is in the stomach, it signals a muscle (pyloric valve) at the base of the stomach to close, and cut off the passage to the small intestine. As long as the pyloric valve remains closed, little or nothing will move out of the stomach and into the small intestine. If alcohol is in the stomach along with the food, the alcohol will also remain trapped in the stomach behind the pyloric valve.

Some of the alcohol trapped in the stomach will begin to break down chemically before it ever gets into the blood, and thus it will not add to a person’s blood alcohol concentration (BAC).

In time, as the digestive process continues, the pyloric valve will begin to open, and some of the alcohol and food will pass through.  Because the alcohol only slowly gets into the blood, and because the body will continue to process and eliminate the alcohol that does manage to get in there, the drinker’s BAC (Blood Alcohol Concentration) will not climb as high as it would have if he or she had drank on an empty stomach.  Also note that high protein foods take longer to digest than low protein foods, thus slowing alcohol absorption even more.

The longer alcohol remains in the stomach during digestion of the food, the more alcohol will break down chemically and will never get to the blood stream. Thus it is important to always eat before drinking alcohol if you want to lessen the amount of alcohol that gets into the blood stream.

In the next segment of this blog, I will discuss how the body distributes alcohol and other practical considerations.  Stay tuned… and until then, be safe.