The absorption process
Unlike food, alcohol does not have to be digested before it can be absorbed into the bloodstream. Alcohol molecules are small and pass quickly and easily into the bloodstream.
Some alcohol – about 20% of whatever enters the stomach – is immediately absorbed through the wall linings of the stomach and into the bloodstream. The rest moves into the small intestine. There it gets absorbed into the bloodstream without undergoing any chemical change of any consequence.
But even though alcohol takes such a quick trip through the body’s digestive route, it doesn’t leave without having made its presence known.
If your stomach is empty and you drink, the alcohol in the drink can possibly irritate your stomach lining. It can prompt the stomach to secrete a protective mucus and also secrete gastric juices. The juices don’t affect the alcohol that much, but they do serve to dilute its concentration in the stomach.
The advice of ’lining your stomach’ before you drink, therefore, makes good digestive sense. Food, particularly protein-rich foods such as milk, meat or eggs protect the stomach lining. Eating these types of food also slows down the process by which alcohol is absorbed because the stomach has to break it down with gastric juice to start the process of digestion.1
Alcohol takes a direct route from mouth to bloodstream, but the speed of absorption can vary.
The pyloric sphincter is a small valve-like structure that lies between the stomach and the small intestine and controls the flow of food between the stomach and the small intestine.
It is also sensitive to trouble signs in the stomach. If a substance is upsetting the stomach, it probably isn’t the sort of thing your body wants your bloodstream to absorb too quickly. So, when the stomach gets irritated, the sphincter will start to get very selective about what does and doesn’t get through.
Alcohol is an irritant to the stomach lining, particularly when the stomach doesn’t have any food to buffer the interaction. At first, the irritation isn’t enough to activate the pyloric sphincter. But if you’re not careful enough how you space your drinks, the irritation level could increase (even though there’s food in the stomach) and the sphincter could simply clamp shut. When this happens the alcohol gets trapped in the stomach. If you continue to eat or drink while the sphincter is closed, you will vomit.