What Actually Happens To Alcohol In Your Body?
We drink alcohol in many different forms. Beer, wine, spirits, cocktails and everything in between. They might taste completely different but there is one thing they all have in common, ethanol.
Ethanol is the type of alcohol found in alcoholic drinks and it is the molecule responsible for most of the effects we associate with drinking. Once it enters the body, the story becomes one of absorption, circulation and eventually breakdown.
Ethanol
When we drink alcohol, the ethanol passes through the stomach and small intestine and enters the bloodstream. From there it is carried around the body. Alcohol doesn't just affect one particular organ. It reaches the brain, muscles, heart, digestive system and other tissues throughout the body via the bloodstream.
The amount of alcohol in the blood is partly determined by how much and how quickly we drink and then how quickly the body can absorb and metabolise it. Metabolising alcohol means the body uses different mechanisms to break down the ethanol molecule into other molecules using enzymes, step by step, until it reaches a format that can be expelled from the body.
The body starts the process of breaking alcohol down very quickly, but absorption into the bloodstream happens faster than the body can usually process it. So if we continue drinking alcohol on a night out at a rate faster than the body can process it, the amount of ethanol circulating in the blood increases.
Breaking Down Ethanol
Most ethanol is broken down in the liver. The first step uses an enzyme called alcohol dehydrogenase, or ADH. This converts ethanol into another chemical called acetaldehyde. Unfortunately, acetaldehyde is highly toxic and is also a known carcinogen. It is so dangerous that if a product was produced with acetaldehyde in it, it would be banned and not fit for consumption.
The body has to protect itself so it uses another enzyme called aldehyde dehydrogenase, or ALDH, which breaks down it down into the harmless acetate (which is essentially vinegar). The acetate is safely burned for energy and eventually is converted into carbon dioxide and water which can be eliminated from the body through urine and breathing.
The body is constantly trying to turn alcohol into something easier to handle. Unfortunately the only way the body can break down ethanol, is by converting it into this highly toxic molecule first.
Why Into A Toxic Chemical?
So why does it have to be converted in a toxic chemical? Because of how alcohol is made in the first place.
When yeast makes alcohol, it goes on a chemical journey. It consumes sugar for energy and pumps out alcohol as a waste product.
The fascinating part? Human metabolism basically runs this exact process in reverse. The human liver uses the exact same biological tools as yeast, but treats alcohol as the starting point instead of the end product. Because our bodies are essentially undoing what the yeast did, we are forced to recreate the toxic acetaldehyde.
While This Is Happening
The interesting part is that ethanol isn't sitting quietly in the body while the liver deals with it. It is actively changing the way the body works. In the brain, ethanol interferes with communication between nerve cells. This can affect judgement, memory, coordination, speech and mood. While we can't always feel it depending our own tolerance levels and how much we drink, the impairment begins from the moment we have the first drink.
In the kidneys, alcohol suppresses the release of vasopressin, a hormone involved in telling the kidneys to retain water. Less vasopressin means more water is released as urine. This is one of the reasons drinking alcohol can leave you dehydrated and contribute to the symptoms of a hangover like dehydration.
Alcohol can also affect the digestive system, cardiovascular system, immune system and pancreas. So although we often talk about getting "drunk" as if alcohol mainly affects the brain and trying to feel that buzz, ethanol is actually travelling throughout the body and interacting with many different systems, and not in a good way.
On balance, there are far more adverse health risks associated with drinking alcohol and very few benefits, if any significant ones, except feeling relaxed.
A Temporary Chemical Change
The effects we notice from drinking are therefore only one part of the story. There is the ethanol entering the bloodstream. There is the brain responding to the ethanol. There is the liver breaking it down. There is the toxic intermediate acetaldehyde being produced and then broken down. And there are all the knock-on effects across the body.
This is why alcohol can produce such a variety of effects. Feeling relaxed, becoming more sociable, losing coordination, needing to urinate more, feeling sleepy and eventually waking up with a hangover are all different consequences of the same substance interacting with the body's systems.
I've written more about some of these individual effects in the other alcohol blogs, including Why we Drink When Feeling Blue, What Actually Causes A Hangover and Why Breaking The Seal Doesn't Make You Pee More.
But underneath all of these different experiences is the same molecule. Ethanol.
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