Summary of what alcohol does to your body, brain and health

No level of alcohol consumption is safe for our health. Here's why.

Summary of what alcohol does to your body, brain and health
Alcohol, whether it's beer, wine or spirits does not only make you tipsy or drunk. It causes cancer, shrinks your brain and makes you dumber (among other things)

This is a summary of the points presented by Andrew Huberman, in one of his YouTube videos.

Please note that:

  • I am not the author, I merely wrote this summary of the points I found interesting!
  • I'm not a health specialist. If you need medical advice/help/assistance/guidance, please consult a real doctor.


Alcohol is far more dangerous than most people assume (myself included!). Many enjoy the social dimension of drinking, the state it puts them in and, of course, the taste. Still, it feels surprising to me that few people are actually aware about the severe risks for health, even with pretty moderate consumption.

Since Andrew Huberman, who is a professor of neurobiology and ophthalmology, published a 2-hours long video about this topic, I thought it would be a good opportunity to learn more about what alcohol really is, and does to our body.

What Alcohol Does to Your Body, Brain & Health
In this episode, I discuss the physiological effects that drinking alcohol has on the brain and body at different levels of consumption and over time.

Of course, I took notes. And here they are!

No level of alcohol consumption is safe for our health

The World Health Organization (WHO) is clear on this topic:

  • Alcohol is a Group 1 carcinogen, at the same level as tobacco
  • The more alcohol one consumes, the more chances they have to get cancer
  • Alcohol can alter DNA methylation and gene expression
      • Alcohol causes many mutations of DNA, leading to cancer, especially as the immune system is weakened and/or is not able to deal with the proliferation of cancerous cells
  • Any type of alcohol (e.g., wine, beer, spirits), even with low consumption (< 3.5 liters of beer or < 1.5 liters of wine or < 450ml of spirits per week!) increase the risks of cancer
      • International Agency for Research on Cancer

Actions one can take to reduce the chances of getting cancer

  • Drink really rarely or not at all. Three to four drinks every month does not seem to cause health issues
  • Consuming folate, B vitamins and B12 in particular, because the lack of those is partially responsible for increasing cancer risks

Alcohol is toxic. It damages/kills cells and disrupts many systems

From a chemical/biological point of view, alcohol's structure is both water-soluble and fat-soluble. When one drinks alcohol, it can pass into all the cells and tissues of the body. It has no trouble just passing into the cells. Alcohol doesn't just attach to the surface of the cells. It has direct effect on the cells as it passes into those. That's why alcohol is damaging.

There are three types of alcohols: isopropyl, methyl and ethyl (aka ethanol). Humans can only drink ethanol. It produces substantial stress and damage to cells (and also kills those!). When one ingests ethanol, it has to be converted into something else because it is toxic to the body. In the body, there is a substance called NAD. Levels of NAD tend to go down across the lifespan. Increased levels of NAD may extend the lifespan. When one ingests ethanol (i.e., alcohol), NAD is involved in converting the ethanol into acetaldehyde, which is even worse than ethanol.

Acetaldehyde is poison. It damages and kills cells (indiscriminately!). The body deals with that problem by using another component of the NAD biochemical pathway to convert acetaldehyde into acetate (which is something the body can use as fuel). That process of going from ethanol to acetaldehyde to acetate does involve the production of a toxic molecule. If our body can't do the conversion of ethanol to acetaldehyde to acetate fast enough, then acetaldehyde will build up in our body and do damage all over. What makes us drunk is the poison created by the conversion: the acetaldehyde.

The conversion ends up creating some energy, but it has no nutritive value. It can't be stored, doesn't provide vitamins, aminoacids or fatty acids. It's truly empty calories. Even sugar is better energy

The body does that conversion in the liver. But the cells of the liver get exposed to acetaldehyde in the conversion process and get damaged/killed. Ingesting alcohol is ingesting a poison, which the body converts into a worse poison.

Alcohol is consumed into the gut, goes into the stomach. The liver immediately starts the conversion of alcohol (cfr next sections), and a portion of the acetaldehyde and acetate go into the brain (crosses the blood-brain barrier, aka BBB):

  • It makes us tipsy, drink and/or energized
  • It goes a bit everywhere, but tends to quickly reduce brain activity in the prefrontal cortex (PFC), and one of the first effects is drastically reduces the ability to suppress impulsive behavior. Once drunk, people pay less attention to what they say, do, their voice modulation (loudness, etc). Inhibitions are lifted, etc
  • It also has a big impact on the neural networks involved in memory formation and storage (hence why people forget)

Alcohol and in particular the toxic metabolites of alcohol increase the conversion of testosterone and estrogen (useful for cognition). It impacts libido, cognition, etc. Related article:

Alcohol is clearly bad for the brain

Alcohol consumption causes neurodegeneration of the neocortex, which is associated with memory, the ability to think and plan, the ability to regulate primitive drives, etc.

Even 1-2 drinks a day (or 14 on the weekend, or 7 on friday...) lead to thinning of the neocortex. It causes a loss of neurons in the neocortex and other brain regions. Gray matter and white matter are both impacted. Related study:

Alcohol reduces the thickness of the brain. The shrinkage varies depending on the consumption levels. Related study:

The more often one drinks, the more permanent changes there are in the brain regarding habitual and impulsive behavior. The effects remain even when not drinking anymore. There are persistent changes.

Alcohol also influences serotonine (a neuromodulator). It changes the activity of neural networks. Serotonin levels have a relationship with the mood. After a few drinks people start having motor issues, issues to speak, start leaning on things, pay less attention, etc. They slowly shut down and end up passing out.

Alcohol also changes the relationship between the hypothalamus and the pituitary gland and the adrenals. Primitive functions are affected: behavior, mindset, rage, sex drive, temperature regulation, appetite, thirst, etc.

Alcohol lowers body temperature by disrupting the parts of the brain that control body temperature. Taking cold showers is a really bad idea, it can be very dangerous (can lead to hypothermia).

Effects on happiness, motivation, and stress

After consuming alcohol, and when it wears off, it leads to a state of being less happy, less motivated, more stressed, etc.

When people drink regularly, they have more stress hormone (cortisol) at the baseline when they're not drinking. They feel more stress and more anxiety when not drinking. Those changes persist long past the time they last drank. It pushes them to drink again to go back to their "previous state". Related study:

What are high levels of alcohol consumption?

12-24 drinks per week or more. Not necessarily evenly split. It could be 7 on Friday, 7 more on Saturday, or 2 per day. It doesn't matter.

  • For men, consuming more than 4 drinks on any day or more than 14 drinks per week
  • For women, consuming more than 3 drinks on any day or more than 7 drinks per week
  • Or simply binge drinking 5 or more days in a month
    • Binge drinking is defined as bringing the Blood Alcohol Concentration (BAC) to 0.08%, or 0.08g/deciliter or higher


When is someone considered an alcoholic

Someone is considered an alcoholic when consuming heavily (cfr previous point) / on a regular basis.

Regular drinkers or people with a genetic predisposition to alcoholism tend to feel energized/in a good mood when they drink. Meanwhile, occasional drinkers will have a less long lasting period of feeling good when they drink and will more quickly transition into a more "lethargic" state. This is distinct from alcohol tolerance.

The timing of those effects can easily show who has a predisposition to alcoholism and who are more regular drinkers. This is interesting to observe in order to be able to warn/help people around us.

People who start drinking younger (14-15) or have relatives who have an issue with alcohol have a higher probability of becoming alcoholics. It can induce a long-lasting dependence on alcohol

Tolerance to alcohol depends on many factors

Chronic tolerance: reduced effects of alcohol with repeated exposure, due to changes in the brain that are the direct consequence of the toxicity of alcohol.

There are also genetic factors, habits and their effects on tolerance, etc. People with gene variants and/or who are chronic drinkers become more alert, feel great, etc when they drink more. Those people who seem to have an amazing time are often future alcoholics or are already alcoholic. They have a much higher treshold. They actually deserve to be warned.

Related paper:

Slowing down the effects of alcohol

Eating before or while drinking alcohol, slows down the absorption of alcohol into the bloodstream. It prevents us from feeling drunk as fast, especially if food includes carbohydrates, fats and proteins. But the effects will come anyway.

If already drunk, it's already in the blood stream (happens within 5-10 minutes). It will reduce the effects of what you drink next.

Helping the body recover

Alcohol dehydrates as it is a diuretic. It causes to excrete not only water, but also sodium (which is critical for neurons). It's important to recharge sodium, potassium and magnesium (electrolytes) for proper brain and organ function. Even the day after drinking few drinks, levels can be too low.

For every drink of alcohol one drinks, they should drink two glasses of water, and even better, water with electrolytes.

Blackout and hangover

Blackout is when one forgets what happened when they were drunk. That is highly concerning as it is heavily linked with severe effects/dangers of alcohol.

Hangover often includes headaches, nausea, anxiety, etc. Alcohol tends to dilate blood vessels. When alcohol wears off, there is vasoconstriction, leading to headaches. Drinking alcohol again does calm the symptoms, but causes more hangover later on.

Alcohol and sleep

Sleep after consuming alcohol is not the good sleep, as explained by Dr Matthew Walker, the author of "Why we Sleep" (a book that I strongly recommend).

When alcohol is in the bloodstream and brain, sleep is disrupted and is not of high quality. Slow-wave sleep, deep sleep, rapid eye movement sleep, are all impacted, while they're essential for a good rest.

Instead of a good night sleep, it's only possible to get into "peudo-sleep".

Alcohol impact on the gut, liver, brain axis

The gut and brain communicate through chemical signaling. The gut and the liver also communicate through neural signaling. The liver also communicates with the brain through chemical signaling and neural signaling.

Alcohol disrupts the microbiome of the gut and its communications. It also severely impacts the immune system. It causes leaky gut. (bad) bacteria from partially digested food in the gut can pass into the bloodstream, and other things being released from the liver. It also gets into the brain, disrupts neural circuits that control regulation of alcohol intake, leading to an increase of alcohol intake. It causes inflammation in different parts of the body and pushes us to drink more

Eating (low-sugar) fermented foods and probiotics can help "repair/reconstruct" the gut microbiome.



Alcohol is far worse than I thought, and I'm thankful that Dr Andrew Huberman presented this information so clearly, and so neutrally. Many people drink for fun, to relax, etc. And many don't realize how dangerous alcohol actually is, beyond its obvious effects...

Hopefully, sharing this information might help others like it helped me. Even if it's a single human, I'll be glad I shared these notes!