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How Alcohol Affects Your Body Alcohol 101, Part 2

How Alcohol Affects Your Body

Alcohol 101, Part 2

How Alcohol Affects Your Body


Welcome to Part 2 of our three-part series on everything you need to know about alcohol. This second part explains the different effects alcohol has on your body, covering topics like why drinking can make you crave junk food and make it so hard to get restful sleep. In part 1 of this series, we covered how your body processes alcohol, and in part 3 we’ll dive into what you can do to help your body out when you’re drinking.

Specifically, let’s take a look at the biochemical effects of drinking alcohol. There are lots of reasons why people – including many of us at ZBiotics – choose to have a drink now and then. Alcohol is social, tasty, cultural, and – when enjoyed responsibly – fun. But there are tradeoffs that we all should understand. Knowing those tradeoffs, and making the decision to drink with that knowledge, is how we can truly drink responsibly.

We’ve discussed before that – contrary to popular belief – alcohol does not cause dehydration, but it does affect our bodies in several important ways.

Note that when we say “alcohol,” we’re referring to the molecule ethanol. There are several other molecules you are exposed to when you drink, but commonly when we think of alcoholic beverages, it is the ethanol that is really the star of the show.

1. Alcohol causes intoxication

This is the obvious one. Alcohol can make you feel buzzed, tipsy, drunk, etc., depending on how much you drink. It creates feelings that range from increased confidence and wellbeing to reduced judgment and more severe impairment. At a high level, intoxication occurs when alcohol inhibits the normal functioning of neurons in your brain, changing the way those neurons communicate with one another.

The amount of intoxication you experience relative to the amount of ethanol you ingest depends on several factors. In addition to how much and how often you drink, things like your sex, genetic makeup, weight, and microbiome can affect how intoxicated you feel.

However, as a general rule, your blood alcohol content will rise approximately 0.02-0.05% per standard alcoholic drink, and your body can metabolize enough alcohol to drop your BAC roughly 0.01-0.02% per hour (i.e. <1 drink per hour).


There are several charts of this variety. This one is from the California’s DMV. These are all rough estimations that don’t take into account your particular body and all the factors that could affect you in a given night, but this serves as a good guide and starting place. Citation.


2. Alcohol exposes us to a known carcinogen

Alcohol is a known carcinogen (i.e. capable of causing cancer). There are very few things in the world that companies can legally sell for consumption that are as toxic to human health as alcohol. It essentially has been grandfathered in by cultural normalcy and the fact that people enjoy it and are willing to accept the tradeoff. But if a drug company today developed ethanol for the first time, there is likely no way that the FDA would allow it to enter the market, given its known health consequences. Of course, that being said, the dose makes the poison, and in moderation the risk is low.

3. Alcohol affects our brains and our sleep

Alcohol can cross the blood-brain barrier (meaning it has direct access to your brain), and it can bind to multiple types of neurotransmitter receptors in the brain. This is how it creates feelings of intoxication. Not surprisingly, this action is also at the root of many of the undesirable side-effects of drinking.

The most notable effect is that alcohol generally disrupts your brain’s ability to regulate feelings of excitement and relaxation, largely by affecting your brain’s GABA and glutamate receptors. This creates a kind of pendulum swing back and forth that initially creates sleepiness, but then periodically will pull you out of your deepest levels of sleep into wakefulness throughout the night. This hurts the quality of your sleep for as long as alcohol is in your system. And it can lead you to feeling tired the next day regardless of how many hours you were asleep (citation).

Put another way, drunk sleep is bad sleep.


Alcohol's Effect on Sleep
Here is an example of alcohol’s effect on a typical sleep cycle. Alcohol decreases the time it takes to fall asleep, and during the first half of the night both increases Stage 4 (slow wave) sleep and suppresses REM sleep. Then, in the 2nd half of the night, the pendulum swing starts, with alcohol increasing wakefulness and interfering with REM sleep. Citation. Chart format adapted from site.


4. Alcohol irritates our gut and disrupts our microbiome

Alcohol is what we use in the lab to sterilize surfaces and equipment of unwanted bacteria and other cells. So it shouldn’t be surprising to learn that the alcohol you drink can irritate the cells that line your stomach and intestines (citation). Nor should it be surprising that alcohol can also disrupt your gut microbiome: the community of good bacteria that live in your gut (citation). This irritation and disruption is responsible for at least part of any stomach aches you might feel when/after you drink, as well as diarrhea and other generally unpleasant trips to the bathroom the next day (vasopressin also plays a role in this, but we’ll get to that later).

5. Alcohol creates imbalances in leptin, vasopressin and other hormones

Alcohol can have a noticeable impact on our appetite and food cravings (we’ve all experienced the “drunken munchies”). This is in part because alcohol affects multiple hormones regulating your appetite. For example, alcohol has an inhibitory effect on leptin, a hormone that suppresses appetite (citation), which contributes to our cravings for late-night junk food after drinking.

As a side note, the full science behind why alcohol causes the “drunken munchies” is fascinating. In addition to its effects on leptin, it includes alcohol’s effects on blood sugar, starvation receptors in your brain (citation), and emotional regulation issues such as inhibition and self-control. But that’s a story for another post…

Beyond leptin and appetite, alcohol inhibits vasopressin, which is a hormone in your body responsible for water recycling and urination (among other things). You may have noticed that it ends up feeling like you have to pee a lot more frequently when you are drinking, and this observation is frequently extrapolated to wild (and scientifically refuted) claims about the extreme dehydrating effects of alcohol. Often, it is alcohol’s impact on vasopressin that is used to justify these claims in numerous blogs and write-ups throughout the internet. However, fascinatingly, your experience of feeling like you need pee more frequently has a lot more to do with how much liquid you’re putting in your body than the alcohol itself (see our full blog piece here on that science).

However, this is not to say that alcohol’s inhibition of vasopressin does not have any effect. Alcohol’s vasopressin inhibition causes another pendulum swing – one that creates wider hormonal imbalances affecting much more than just urination. Alcohol’s impact on vasopressin could be responsible for all kinds of effects as your endocrine system rebalances. These include feelings of anxiety, changes in your tolerance for alcohol, and changes in your cravings for alcohol (citation).

6. Alcohol leads to accumulation of the toxic byproduct acetaldehyde

As noted in several places on the ZBiotics website and blog, a relatively small but ultimately impactful amount of the alcohol you drink is converted to acetaldehyde in your body, mostly by your microbiome. While this is only a small amount of acetaldehyde, this molecule is extremely toxic. It generally wreaks havoc throughout your body, causing all sorts of nasty effects – many of which are felt the day after drinking.

We won’t go into detail on acetaldehyde here, but you can find more info in our science section.

In summary

Alcohol doesn’t just make you intoxicated; it affects your sleep, your appetite and cravings, your mood, your decisions, and so much more. That’s because alcohol affects a wide range of systems in your body, including your brain, your hormone levels, and your gut microbiome.

However, when used in moderation and alongside responsible drinking behaviors, it can be a positive part of adult behavior. We believe that knowing how alcohol affects us helps us make better decisions.

In the next and final part of this series, we will dive into some behaviors specifically designed to help with these known biochemical effects, so you can have your night out and enjoy a full next day too!


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