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How alcohol affects the human body

For the purposes of this article, you can loosely assume that alcohol = ethanol

He is out. Young man passed out on bean bag with joystick in his hand, in messy room after a party
He is out. Young man passed out on bean bag with joystick in his hand, in messy room after a party
Alcoholic drinks are one of the many perks of living in the modern world, and they can act as stress reducers if consumed in just the right quantity. Since we human beings generally have a tough time limiting ourselves to a moderate dose of things that feel or taste good, some of us will inevitably have a bit too much to drink at some point in our lives. I’m assuming that most of us know what a hangover feels like, but for the ultra disciplined amongst us (who have so far managed to resist drinking too many alcoholic drinks in one sitting), here’s a brief description. A hangover is the general “yucky” feeling a person experiences after a long night of far too much drinking. A hangover generally means being very tired, dehydrated, having a pretty persistent headache, having trouble focusing on or remembering anything, and just generally feeling like shit as your body struggles to recover from the abusive amount of alcoholic beverages you fed it the night before. From all we’ve learnt so far, I think it is fair to say that alcohol can either be a friend that helps you relax after a hard day, or it can be an enemy that will eventually poison you (to death in some cases) if you consume too much of it too quickly. The way the laws of nature keep repeating themselves time and time again is truly uncanny, and alcohol intake follows one of those general rules which advocates for everything in moderation.

The active ingredient in alcoholic drinks is called “ethanol” or “ethyl alcohol” (chemical formula – C2H5OH). Ethanol is a relatively small chemical compound that is very hydrophilic. The word hydrophilic comes from the greek words “hydr” which means water, and “philos” which means love. So in plain english, saying that ethanol is hydrophilic simply means it “loves water enough to be easily miscible or dissolvable in it”. In the world of solubility or miscibility, like usually mixes with like. So polar compounds mix well with other polar compounds while non-polar compounds mix well with other non-polar compounds. Since ethanol and water are both polar, they mix easily with each other. The chemical reason why ethanol is readily miscible with water is because the alcohol (or O-H) group in its chemical structure allows it to easily form hydrogen bonds with water. The hydrophilic nature of ethanol is a big reason why alcoholic drinks get so easily absorbed into our “mostly-made-up-of-water” bodies, and can cause all that havoc if we drink excessively.

Since both water and ethanol are polar molecules, they mix well with each other. The Hydroxyl (O-H) group on the ethanol molecule forms hydrogen bonds with the oxygen and hydrogen atoms that form each water molecule.
Since both water and ethanol are polar molecules, they mix well with each other. The Hydroxyl (O-H) group on the ethanol molecule forms hydrogen bonds with the oxygen and hydrogen atoms that form each water molecule.

Speaking of alcohol induced havoc, I have always wondered why drinking alcohol unfailingly increases the frequency of urination in the average person. Equally puzzling is understanding the scientific reason behind each dreadful hangover. Let’s spend some time together and examine the scientific reasons behind these phenomena, breaking them down into plain english where appropriate.

Why does drinking alcohol make you urinate often?

Most of us over the age of 21 would have experienced this one. Ever notice how there is always a line for the bathroom at pretty much every bar anywhere in the world that serves alcoholic drinks? Ever notice how much more often you have to urinate when you drink a substantial amount of alcohol (i.e. 2+ glasses of wine) in one sitting? The scientific reason for this is as follows…

The majority of the ethanol you consume through your alcoholic drinks gets absorbed into your bloodstream via the small intestines. Once in the bloodstream, ethanol has access to many of your other organs, one of them being the command center of your body – your brain. Near the base of your brain, there is a gland called the pituitary gland. One of the chief functions of the pituitary gland is to secrete a hormone called vasopressin. Vasopressin is an anti-diuretic hormone… or in plain english, a hormone that limits urination. Under normal circumstances, when your body senses that its stores of water are running low, the pituitary gland will produce vasopressin which will cause water reabsorption in the kidneys and limit the amount of urine you expel from your body. All of this has the net effect of keeping you from urinating until you get completely dehydrated. When alcohol is consumed however, it enters the bloodstream and causes the pituitary gland to block the production of vasopressin. Without vasopressin, the kidneys will keep sending water straight to the bladder which makes you urinate more often instead of causing some amount of water reabsorption back into the body. This is why if you are out on the town for a night of drinking, you usually have to go to the bathroom quite often. Especially once you’ve broken the seal… i.e. the first time you urinate after your first sip of alcohol for the night.

As you probably already know, frequent urination during a relatively large block of time without adequate replenishment of water and electrolytes will eventually lead to dehydration. Moderate to serious dehydration happens to be one of the major symptoms of a hangover… a nice segue to the next section where we’ll take time to understand how hangovers come about.

Why on earth do we get hangovers?

The scientific name for a hangover is veisalgia, from the Norwegian word for “uneasiness following debauchery” (kveis) and the Greek word for “pain” (algia). I laughed out loud after typing that last sentence because it is very very apropos! Most people report having pretty bad headaches, upset stomachs, and just generally feeling really tired among the many other symptoms of an alcohol induced hangover. If you’re like me, you have probably asked yourself some of the following questions at some point in your adult life. Why do we get hangovers? How can something that looks as non threatening as the clear fluid known as alcohol cause our bodies to react so strongly after we’ve had a bit too much of it to drink in some cases? And what can we do to prevent or minimize the effects of a hangover? Well to get a nice vivid picture that answers all these very astute questions, let’s spend some time getting acquainted with the way our bodies process alcohol, and the general physiological effects that excessive amounts of alcohol can have on the human body.

While drinking alcoholic drinks can make a night out on town much more enjoyable for the average human’s emotional psyche, the physical human body doesn’t quite “see” it that way. As a matter of fact, alcohol is really just poison as far as the human body is concerned and it really doesn’t take much pure alcohol to elevate your BAC (blood alcohol concentration) to dangerous levels that can actually kill you. For this reason, most alcoholic drinks have only a small amount of alcohol in them by composition. It is not at all wise to consume pure alcohol on its own. Below are a few examples of some alcoholic drinks, and the usual range of their percent alcohol content:

  • Beer (4 – 6%)
  • Wine (7 – 15%)
  • Champagne (8 – 14%)
  • Liquors such as Vodka and Rum (40 – 95%)

In biological parlance, a poison is something that will harm the body and perhaps force it to shut down unless it is somehow converted into something a lot less harmful. And yes, you guessed it… that is exactly what the body will try to do after you have consumed an alcoholic drink. Unlike many other substances we ingest, such as proteins, fats, and carbohydrates, alcohol cannot be stored in the body without dire consequences. As a result, when we ingest alcohol, processing it becomes a very high priority. This is to prevent the alcohol we have ingested from poisoning our bodies. When you consume alcoholic drinks, the first thing that happens is that the alcohol is absorbed into your bloodstream through the small intestines. The body detects this and “realizes” that it has to metabolize (break down and clear out) the alcohol from your system. A small percentage of the alcohol we consume is eliminated via excretion through the breath, urine, sweat, feces, milk, and saliva. If we think about it for a second, we’ll realize the reason behind a few things we’ve probably all heard of in the past. For one, the reason why nursing mothers are expressly forbidden from drinking alcohol is because some of it is excreted through breast milk. Needless to say, it is probably a bad idea to give a newborn child breast milk that is laced with alcohol. Secondly, the fact that some alcohol is excreted through the breath and mouth is the chief reason why breathalyzers work. The more alcohol you’ve consumed, the more intense the signal picked up by the breathalyzer will be when you blow into it. Although some of the alcohol we consume is excreted from the body via the modes discussed above, the primary means by which alcohol is removed from the body is via an organ called the liver. The liver is responsible for the elimination – through metabolism – of 95% of the alcohol you put into your body.

During the first step of alcohol elimination in the liver, the hepatic (hepatic simply means “of the liver”) enzyme called alcohol dehydrogenase converts alcohol to acetaldehyde through a process called an oxidation reaction. An oxidation reaction in plain english just means a chemical reaction that results in an increase of the ratio between the oxygen atom(s) and the hydrogen atom(s) in a given chemical compound. This can either mean the removal of a hydrogen atom or the addition of an oxygen atom to the chemical compound being oxidized. Acetaldehyde (what is created as a result of ethanol reduction) is a very unstable compound that happens to be even more toxic than ethanol itself. It quickly forms free radical structures which are highly toxic if they aren’t quickly neutralized by antioxidants such as ascorbic acid (Vitamin C) and thiamine (Vitamin B1). These free radicals can cause damage to embryonic neural crest cells, leading to severe birth defects… a strong reason why pregnant women are advised to stay away from alcohol while pregnant. To prevent all this carnage from breaking loose in the body, acetaldehyde is further oxidized almost immediately by another enzyme called acetaldehyde dehydrogenase in the liver to form acetic acid. Acetic acid is eventually broken up into carbon dioxide (CO2) and water (H2O) in the body… two chemical compounds that the body is very adept at dealing with.

The oxidation reaction which occurs in the liver to convert ethanol (which is toxic to the body) into acetic acid which is harmless.
The oxidation reaction which occurs in the liver to convert ethanol (which is toxic to the body) into acetic acid which is harmless.

Although the body has a robust mechanism for getting rid of alcohol, there is a “speed limit” to how quickly it can eliminate alcohol. Generally speaking, the average person can eliminate about 0.5 oz (15 ml) of alcohol per hour. So, it would take approximately one hour to eliminate the alcohol from a 12 oz (355 ml) can of beer with ~4% alcohol content. Several factors can influence this rate of elimination. The rate of elimination tends to be higher when the blood alcohol concentration in the body is very high. This makes sense because at that level of intoxication, the body has to work extra hard in an attempt to prevent you from poisoning yourself. People who drink often and have developed a high tolerance to alcohol as a result, may metabolize alcohol at a significantly higher rate than average, provided they haven’t already destroyed their livers with excessive drinking. This next point is the one I can personally relate to most… the body’s ability to quickly metabolize alcohol (sadly) tends to diminish with age… a big reason why we tend to suffer from more hangovers as we get older. All of this means that if you consume alcohol too quickly, your body won’t be able to eliminate all of it through the usual enzymatic pathway in the liver. The residual amount of alcohol left in your system after a night of heavy drinking is one of the chief reasons for a hangover.

When there is residual alcohol left in your body because your body cannot clear out the alcohol you put in it quickly enough, a lot of other systems in the body suffer as a result. It is pretty straightforward to understand some of the discomfort people experience as a result of too much alcohol intake. For example, a lot of folks will vomit and experience diarrhea after a night of heavy drinking. The simple reason for these forms of discomfort is because the body is trying like hell to expel as much of the poison that you put in it a couple of hours prior. On the other hand, one of the other after effects of too much alcohol consumption is particularly puzzling. I’ve always wondered why people feel tired after a heavy night of drinking even though they might have had the opportunity to get a lot of sleep (from 8 – 12 hours) after a night out on the town.

General tiredness usually occurs the day after a night of heavy drinking because the drinker won’t be able to get into the deep healing phase of sleep as the body will still be struggling to recover from alcohol’s depressive effect on the system. Consuming a lot of alcoholic drinks in a relatively short period of time inhibits your body’s natural ability to create one of its natural stimulants – an amino acid called glutamine. Glutamine production is limited because the body is too busy trying to eliminate alcohol as quickly as possible from your system. When you stop drinking, the body tries to compensate for this by producing more glutamine than it needs. The resulting spike in glutamine levels stimulates the brain while you are trying to sleep. The net effect of this is that it keeps you from reaching the deepest, most healing levels of slumber. This is a big reason why you still feel tired the day after a night of heavy drinking even though you might have slept for 12 hours straight! Further, it may actually explain why people who frequently drink too much look a lot older than they actually are. Perhaps such people have gone too many nights without the deepest levels of healing slumber, making their bodies age at a faster rate.

How to avoid a hangover

Well there is really only one surefire way to completely avoid a hangover, and that is to not drink at all. But what the heck Chuba?… Where’s the fun in that?

Well, the following steps below usually help mitigate the effects of a hangover


  • Try to eat a full meal before you go out drinking. Having a full stomach will slow down the absorption of alcohol into the body. Fatty foods and carbohydrate rich meals seem to work best for most people.
  • Take multivitamins that buffer against vitamin depletion which comes about as a result of excessive urination. Also, some vitamins (such as Vitamin E, Vitamin C, and beta carotene) are antioxidants which limit the damage caused by free radicals (remember that acetaldehyde which is a byproduct of alcohol oxidation can cause the formation of free radicals which are harmful to the body).


  • Drink in moderation. No more than 1 drink/hour. It takes the body about that long to get rid of the toxins.
  • Drink a glass of water after each beverage… keeps you hydrated and dilutes the toxins found in your alcoholic drinks.
  • Try not to mix drinks. If you’re having a beer night, drink only beer. If you’re having a wine night, drink only wine. The worst thing you can do is start with two mojito’s, then on to three glass of sauvignon blanc, and finish the night off with 2 whiskey sours.

Morning After:

  • Eat a healthy and pretty big breakfast with eggs, bananas, and plenty of water or a sports drink. This will help you replenish some of the electrolytes, nutrients, and minerals you would have lost as a result of your relatively high alcohol intake.


In conclusion, alcoholic drinks are like most things in our universe… If you use them in the right amount, they can make your life more pleasant. If you overdo it however, alcoholic drinks can turn into your worst enemy with the potential to actually poison you to death. The truth (and good news) is that alcohol cannot bring any harm to you unless you willingly give your power away to it. On that note, I’ll sign off. Take care of yourselves, and each other. Oh, and please remember to drink responsibly.
Without Wax
Oyolu B.C. Ph.D.
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2 thoughts on “How alcohol affects the human body

  1. Will it be possible to devise procedures to prevent most or all of the annoying effects of alcohol molecules, or will that require humans to switch to different recreational drugs? So I’m imaging something that would allow humans to drink, become drunk, and then reverse it at will and wake up fresh the next day. It seems like one way would be a blood transfusion, replacing the ethanol-poisoned blood with ethanol-free blood taken earlier? Alternatively is there any hope for adding something to the blood stream which converts alcohol to byproducts which cause neither drunkenness nor the classic poisoning symptoms? The other route might be to ween people off alcohol and onto synthetics; I believe that David Nutt in the UK is one person who has advocated/looked into that, e.g. Of course we’ve already discovered several interesting synthetics, but they tend to be legislated against very rapidly.

    1. Hi Dan, Thanks for the very detailed and thoughtful comment! One could imagine a synthetic oxidizing agent that specifically targets alcohol and acetaldehyde. This theoretical oxidizing agent could perhaps be administered intravenously which may speed up the process of clearing out alcohol and acetaldehyde from the system. There are a few issues with this line of thought… for one, you’d have to make sure that this oxidizing agent was somehow exclusively targeted to affect only the alcohol and acetaldehyde that was introduced to the body via an alcoholic beverage. It would be bad if several biochemical reactions in the body kept getting thrown off kilter because a foreign oxidizing agent kept interfering with them… this could potentially spell doom on a much larger scale for the human body. And yes, you bring up a very salient point when remarking that the politics of getting such a synthetic drug (assuming we could actually successfully make one) onto the market aren’t trivial.

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